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V’
Enera,.The
Worldwatch
.by:
in Asia
Paper No. 11
Denis Hayes
Published by:
Worldwatch Institute
1776 Massachusetts Ave., N.W.
Washington, DC 20336 USA
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Denis Hayes
nergy: The Solar Prospect Denis Hayes
Worldwatch Paper 11
March 1.977
This paper is adapted from the author’s forthcoming
book,
Rays of Hope: The Transition
to u Post-Petroleum
World
(W. W. Norton, 1977). The section on “Plant Power” is
adapted from an article that will appear in BioScience in mid,-he remainder of the paper may be partially reprouuced with acknowledgement
to Worldwatch Institute.
The views and conclusions contained in this document are
those of the author and do not necessarily represent those of
Worldwatch Institute, its directors, officers, or staff.
Library
Q Copyright Worldwatch Institute, 1977
of Congress Catalog Card Number 77-72418
ISBN 0-916468-10-O
Printed on recycled paper
‘IC’aLleof Contents
Dawnof
anEra . . . . . . . . . . . . . . . . . . . ._. . . . . . , . . . . . . . . . . . . . 5
Soiar Heating and Cooling
................................
Electricity from the Sun. .................................
Catching the Wind
.....................................
Falling Water ..........................................
Plant Power
..........................................
Storing Sunlight
.......................................
13
.21
.28
.35
..4
0
.57
Turning Toward the Sun. ..................................
61
Notes .................................................
67
ii
Dawn of an Era
a
bout one-fifth of all energy used arou’nd the world now comes
from solar resources: wind power, water power, biomass, and
direct sunlight. By the year 2000, such renewable energy
sources could provide 40 percent of the global energy
budget; by 2025, humanity could obtain 75 percent of its energy from
solar resources. Such a transition would not be cheap or easy, but its
benefits would far outweigh the costs and difficulties. The proposed
timetable would require an unprecedented worldwide commitment of
resources and talent, but ihe consequences of failure are similarly unprecedented. Every essential feature of the proposed solar transition
has already roven technically viable; if the SO-year timetable is not
technical.*
met, the roa crblocks will have been political-not
Different solar sources will see their fullest development in different
regions. Wind pow& potential is greatest in the temperate zones
while biomass flourishes in the tropics. Direct sunlight is most intense in the cloudless desert, while water power depends upon mountain rains. However, most countries have some potential to harness
all these renewable resources, and many lands have begun to explore
the feasibility of doing so.2
A major energy transition of some kind is inevitable. For rich lands
and oar alike, the ener y patterns of the past are not rologue to
the Puture. The oil-base f societies of the industrial worl B cannot be
sustained and cannot be replicated; their spindly foundations, anchored in the shifting sands of the Middle East, have beguil to erode.
Until recently most poor countries eagerly looked forward to entry
into the oil era with its airplanes, diesel tractors, and ubiquitous
automobiles. However, the fivefold increase in oil prices since 1973
virtually guarantees that the Third World will never derive most of its
energy from petroleum. Both worlds thus face an awesome discontinuity in the production and use of energy.
In the past, such energy transformations
invariably produced farreaching social change. The 18th-century substitution of coal for
wood and wind in Europe, for example, accelerated and refashioned
the industrial revolution. Later, the shift to petroleum altered the
nature of travel, shrinking the planet and reshaping its cities. The
coming energy transition can be counted upon to fundamentally alter
tomorrow’s world. Moreover, the quantity of energy available may,
in the long run, prove much less important than where and how this
energy is obtained.
Since many energy sources besides the sun could replace oil and gas,
we need to know now what consequences the choices we make today
will have in 50 years. While we can obviously possess no detailed
information about the state of the world SO years from now, even
rough calculations may yield insights of importance for energy
policy. If we optimistically
assume that the world’s population will
level off after one more doubling and stabilize at eight billion by
2025, and if we conservatively assume that per capita energy use will
then amount to one-third the current U.S. level, we can broadly assess
different ways of trying to meet this aggregate demand.3
If this energy were all provided by coal, an absolutely intractable
problem would result. Coal combustion necessarily produces carbon
dioxide and adding CO2 to the air raises the earth’s temperature by
retarding the radiation of heat into space (a phenomenon known as
the reenhouse effect). Since CO2 remains in the atmosphere for
h un Idre s or perhaps thousands of years, the impact of CO2 emissions is cumulative and irreversible on any relevant time scale. At our
projected level of coal consumption, the atmospheric inventory of
CO2 would increase about 4 percent a year; such growth in atmospheric carbon dioxide would, virtually all meteorologists agree, soon
alter the heat balance of the entire pianet dramatically.
If the postulated energy demand were met with nuclear fission, about
15,000 reactors as large as the biggest yet built would have to be con-
strutted-one
new reactor a day for SO years. Sustaining these reactors would require the recycling of 20 million kilograms of plutonium
annually. Every year, enough plutonium would be recycled around 7
the world to fabricate four million Hiroshima-size bombs. Such a
prospect cannot sanely be greeted with equanimity.
Nuclear fusion is a speculative technology. No one knows what it
will cost, how it will work, or even whether it will work. The deuteriurn-tritium reaction-the “simplest” fusion reaction and the focus of
almost all current research-will
reduce large amounts of radioactive
waste and can be used to bree B plutonium. Some advanced fusion
cycles-most notably those that would fuse two deuterium nuclei or
that would fuse a proton with a boron atom-could,
theoretically,
provide a nearly inexhaustible supply of relatively clean power. But
such reactions will be vastly more difficult to achieve than the deuterium-tritium
reaction. In short, there is no chance that most of the
world’s energy demand will be met by fusion in 2025.4
Thus we are left with the solar options: wind, falling water, biomass,
and direct sunlight. Fortunately, they are rather attractive. Solar
sources add no new heat to the global environment, and-when
in
equilibrium-they
make no net contribution
to atmospheric carbon
dioxide. Solar technologies fit well into a political system that emphasizes decentralization, pluralism, and local control.
Sunlight is abundant, dependable, and free. With some minor fluctuations, the sun has been bestowing its bounty on the earth for more
than four billion years, and it is expected to continue to do so for
several billion more. The sun’s inconstancy is regional and seasonal,
not arbitrary or political, and it can therefore be anticipated and
planned for.5
Our ancestors captured the sun’s energy indirectly by gathering wild
vegetation. Their harvest became more reliable with the revolutionary
shift to planned cultivation and the domestication of animals. As
civilization developed, reliance upon the sun grew increasingly circuitous. Slaves and draft animals provided a roundabout means of
harnessing large quantities of photosynthetic
energy. Breezes and
currents-both
solar-powered
overseas travel.
8
phenomena-drove
milis
and invited
In earlier eras, people were intensely aware of the sun as a force in
their lives. They constructed buildings to take advantage of prevailing winds and of the angles at which the sun’s rays hit the earth.
They built industries near streams to make power-generation
and
transport easier. Their lives revolved around the agricultural seasons.
In the 14th century, coal began to contribute an increasing fraction
of Europe’s energy budget-a trend that accelerated greatly in the
18th and 19th centuries. During the past 75 years, oil and natural gas
became the principal energy sources in the industrialized world. In
the fossil fuel era, the sun has been largely ignored. No nation includes the sun in its official energy budget, even though all other
energy sources would be reduced to comparative insignificance if it
were. We think we heat our homes with fossil fuels, forgetting that
without the sun those homes would be -240" C when we turned on
our furnaces. We think we get our light from electricity, forgetting
that without the sun the skies would be permanently black.6
About 1.5 quadrillion megawatt-hours of solar energy arrive at the
earth’s outer atmosphere each year. This amount is 28,000 times
greater than all the commercial energy used by humankind. Roughly
35 percent of this energy is reflected back into space; another 18
percent is absorbed by the atmosphere and drives the winds; and
about 47 percent reaches the earth. No country uses as much energ
as is contained in the sunlight that strikes just its buildings. Indee (Y,
the sunshine that falls each year on U.S. roads alone contains twice
as much energy as does the fossil fctel used annually by the entire
world. The wind power available at prime sites could produce several
times more electricity than is currently generated from all sources.
Only a fraction of the world’s hydropower capacity has been tapped.
As much energy could be obtained from biomass each year as fossil
fuels currently provide.
How easily and cheaply these vast energy sources can be harvested is
disputed. Opinions naturally rest heavily upon the questions asked
and the assumptions made. How much distance can separate an ener-
“No country uses as much energy as is
contained in the sunlight that strikes
just its buildings.”
gy facility and its potential users? Will people and industries migrate
to take advantage of new energy sources? Should only huge, utilityscale sites be considered or should individual and community-sized
sites be counted as well? What limits will environmental, political, and
aesthetic factors impose?
Past efforts to tap the solar flow have been thwarted by unreasonable
economic biases. The environmental costs of conventional fuels, for
example, have until recently been largely ignored. If reclamation were
required of strip mining companies, if power plants were required
to stifle their noxious fumes, if oil tankers were prohibited from
fouling the oceans with their toxic discharges, if nuclear advocates
were forced to find a safe way to dispose of long-lived radioactive
wastes, conventional power sources would cost more and solar equipment would be more economically competitive. As such costs have
been increasingly “internalized,”
conventional sources have grown
more expensive and solar alternatives have consequently become
more credible.7
Moreover, fuel prices long reflected only the costs of discovery, extraction, refining, and delivery; they failed to include the value of the
fuel itself. Over the years, improvements in exploitation techniques
drove fuel prices relentlessly downward, but these low prices were
chimerical. Although, for example, U.S. oil prices (corrected for inflation) fell 37 percent in the 25 years between 1948 and 1972, the nation was living off its energy capital during this period-not
its interest. The world has only a limited stock of fuel, and it was only a
rl1,~ ’ ‘T- ?F !: -;e ltlore
that fuel began to run out.8
Unlike finite fuels, sunlight is a flow and not a stock. Once a gallon
of oil is burned, it is gone forever; but the sun will cast its rays
earthward a billion years from now, whether sunshine is harnessed
today for human needs or not. Technical improvements in the use of
sunlight could lower prices permanently; similar technical improvements in the use of finitc fuels could hasten their exhaustion.
The current world economy was built upon the assumption that its
limited resources could be expanded indefinitely. No nation charged
10
OPEC-style severance royalties when oil was removed from the earth;
depletion allowances were granted to those who exploited it. No nation charged a reasonable “scarcity rent” for fuel; the needs of future
generations were discounted to near zero. Now tha: the world’s remaining supply of easily obtainable high-grade fuel is mostly in the
hands of single-resource nations with legitimate worries about their
long-range futures, prices have increased fivefold in five years. As a
consequence, solar energy is ra idly shaking off the false economic
constraints that previously hin dPered its commercial development. In
1976, the Uni+ Ad States produced one million square feet of solar
collectors; in 1977, the figure is expected to triple.9
Since sunlight is ubiquitous and can be used in decentralized facilities,
many proposed solar options wou!d dispense with the expensive
transportation and distribution networks that encumber cor,ventional
energy systems. i0 The savings thus obtained can be substarltial;
transmission and distribution today account for ,lbout 70 ercent of
the cost of providing electricity to the average U.S. resi f ence.” Ii1
addition, line losses during electrical transmission may amount to
several percent of all the energy produced, and the unsightly transmission tendrils that link centralized energy sources to their users
are vulnerable to both natural disasters and human sabotage.
Probably the most important element in a successful solar strategy
is the thermodynamic matching of appropriate energy sources with
compatible uses. The quality of energy sought from the sun and the
costs of collecting, converting, and storing that energy usually correlate directly: the higher the desired quality, the higher the cost.
Sources and uses must therefore be carefully matched, so that expensive, high quality energy is not wasted on jobs that do not require it.12
No country has undertaken a comprehensive inventory of the quality
of energy it uses throughout its economy. Moreover, the energy currently employed for various tasks is often of far higher qualit than
necessary. The use of nuclear rea tors operating at a million d egrees
C to make electricity to run resid-2ntial water heaters to provide bath
water at 30" C is surely the height of thermodynamic foolishness.
Preliminary calculations suggest that roughly 34 percent of end-use
energy in the United States is employed as heat at temperatures under
100” C; much of this energy heats buildings and provides hot water.
Another 24 percent is for heat at temperatures of 100" C or higher,
much of it for industrial processes. Thirty percent of end-use energy
is employed to power the transportation system; 8 percent is used as
electricity and 3 percent as miscellaneous mechanical work. In Canada, a somewhat higher percentage is used for low-grade heat and
somewhat less is used for transportation. Although both countries
are highly industrialized, highly mobile, and have high energy useGNP ratios, most of the energy budgets of both could easily and
economically be met using existing solar technologies.13
Cheap, unsophisticated coliectors can easil-. provide temperatures up
to 100" C. Selective surfaces-thin,
space-age coatings that absorb
much sunlight but re-radiate negligible heat-greatly
increase the
temperatures that collectors can attain. Because air conducts and convects heat, high-temperature collectors are often sealed vacuums. Focusing collectors, which use lenses or mirrors to focus sunlight into a
small target area, can obtain still higher temperatures. The French
solar furlrace at Odeillo, for instance, can reach temperatures of about
3ooo"c.
Solar thermal-electric plants appear economically sound, especially
when operated only to meet daytime peak demands or when crossbred
with existing plants that use other fuels for night-time power production. Ocean thermal facilities may be a source of base-load electricity in some coastal areas. Decentralized photovoltaic cells will be
the most attractive source of solar electricity if the cost reductions
commonly projected materialize.
Wind power can be harnessed directly to generate electricity. But
because electricity is difficult to store, some wind turbines might best
be used to pump water into reservoirs or to compress air. The air and
water can then be released as needed to generate electricity or to Perform mechanical work. Energy from intermittent sources like wind
machines can also be stored as high temperature heat or in chemical
fuels, flywheels, or electrical batteries.
11
12
Biological energy sources, which include both organic wastes and fuel
crops, could by themselves yield much of the worid’s current energy
needs. Such sources can provide liquid and gaseous fuels as well as
direct heat and electricity. Particularly attractive in a solar economy
would be the use of biomass for the co-generation of electricity and
industrial process steam.
While no single solar technology can meet humankind’s total demand
for energy, a combination of solar sources can. The transition to a
solar era can be begun today; it would be technically feasible, economically sound, and environmentally
attractive. Moreover, the most
intriguing aspect of a solar transition might lie in its social and
political ramifications.14
Most policy analyses do not encompass these social consequences of
energy choices. Most energy decisions are based instead on the naive
assumption that competing sources are neutrai and interchangeable.
As defined by most energy experts, the task at hand is simply to obtain enough energy to meet the projected demands at as low a cost
as possible. Choices generally swing on small differences in the
marginal costs of competing potential sources,
But energy sources are not neutral and interchangeable. Some energ
sources are necessarily centralized; others are necessarily disperse J .
Some are exceedingly vulnerable; othc.rs are nearly impossible to disrupt. Some will produce many new jobs; others will reduce the number of people employed. Some will tend to diminish the gap between
rich and poor; others will accentuate it. Some inherently dangerous
sources can be permitted widespread growth only under authoritarian
regimes; others can lead to nothing more dangerous than a leaky
roof. Some sources can be comprehended only by the world’s most
elite technicians; others can be assembled in remote villages using
local labor and indigenous materials. Over time, such considerations
may prove weightier than the financial criteria that dominate and
limit current energy thinking.
Appropriate energy sources are necessary, though not sufficient, for
the realization of important social and political goals. Inappropriate
“Most energy decisions are based on the
naive assumption that competing sources
are neutral and interchangeable.”
energy sources could make attaining such goals impossible. Decisions
made today about energy sources will, more than most people imagine, determine how the world will look a few decades hence. While
energy policy has been dominated by the thinking of economists and
scientists, the crucial decisions will be political.
The kind of world that could develop around energy sources that are
efficient, renewable, decentralized, simple, and safe cannot be fully
visualized from our present vantage point. Indeed, one of the most
attractive promises of such sources is a far greater flexibility in social
design than is afforded by their alternatives. Although energy sources
may not dictate the shape of society, they do limit its range of possibilities; and dispersed solar sources are more compatible than centralized technologies with social equity, freedom, and cultural pluralism. All in all, solar resources could power a rather attractive world.
Solar Heating and Cooling
Solar energy is most easily captured as low-grade heat. Development
of the flat-plate collector that is used ,to catch such heat is generally
credited to the 18th century Swiss scientist Nicholas de Saussure,
who obtained temperatures over 87” C using a simple wooden box
with a black bottom and a glass top. ‘Ine principle used by de Saussure is simple: lass is transparent to sunlight but not to the radiation
of longer wave Bengths given off by the hot collector itself. Sunlight
flows easily through the glass top into the collector where it is
trapped as heat. The modern flat-plate collector operates on this same
basic principle, although im roved materials achieve much higher
temperatures and are more crurable. Simple and easy-to-make solar
collectors could supply heat now
rovided by high-quality
fuels.
More than one-third of the energy lYudget of all nations is spent to
produce heat at temperatures that flat-plate solar collectors can
achieve.15
The simplest task to accomplish directiy with solar power is heating
water, and solar water heaters are being utilized in many countries.
More than two million have been sold in Japan, and tens of thou-
13
14
sands are in use in Israel. In the remote reaches of northern Australia,
where fuels are expensive, solar water heaters are required by law on
all new buildings. Until replaced by cheap natural gas, solar water
heaters were much used in California and in Florida; Miami alone had
about 50,000 in the early 1950s. Since 1973, interest in solar water
heaters has rekindled in many parts of the world. In poorer ~ou:;~tries,
cheap hot water can make a significant contribution to public wellbeing: hot water for dishwashi’ng and bathing can reduce the burden
of infectious diseases, and clothes washed with hot water and soap
outlast clothes beaten clean on rocks at a river’s edge.
Sunlight can also be used to heat buildings. All buildings receive and
trap radiant energy from the sun. Warming a home on a winter day,
this heat may be desirable; but it can constitute indecent exposure,
broiling and embroiling the occupants of an all-glass office building
in mid-summer. Solar buildings, designed to anticipate the amount of
solar energy available in each season, put sunlight to work. To harness diffuse solar energy to meet a building’s needs, options that vary
in efficiency, elegance, and expense can be employed.‘6
Solar heating systems for buildings can be either “active” or “passive.” in active systems, fans and pumps move air or liquid from
a collector first to a storage area and then to where it is needed. Passive systems store energy right where sunlight impinges on the building’s structural mass; such systems are designed to shield the structure from unwanted summer heat while capturing and retaining the
sun’s warmth during the colder months. Passive solar buildings act
as “thermal flywheels,” smoothing the effects of outside temperature
fluctuations between day and night-a principle as old as the ancient
thick-walled structures of Mohenjo-Daro in the Indus Valley and the
adobe Indian pueblos in the American Southwest. Although more
money and attention has been lavished upon active systems, many
of the world’s most successful solar buildings employ simple, inexpensive passive designs.
In the latitudes that girdle the Earth between 35” N and 35” S, roofs
of buildings can be built to serve as passive solar storage devices.
For this region, American designer Harold Hay has built a “sky-
therm” house, the flat roof of which is covered by large polyethylene
bags filled with water. By adroitly manipulating slabs of insulation
over the roof during the day or night, Hay can heat the house in the
winter and cool it in the summer. A.K.N. Reddy and K.K. Prasad at
the Indian Institute of Science in Bangalore have suggested a similar,
but less expensive design for poor countries; their model uses rooftop
ponds of water.
In latitudes above 35” either north or south, a flat roof can catch
less and less of the low winter sun. Vertical walls and steep roofs are
more effective solar collectors in these regions than are flat roofs. In
France, Felix Trombe and Jacques Michel have built several solar
houses, each with a glass wall facing south and a thick concrete wall
located a short distance inside the glass. Openings near the top and
bottom of the concrete walls create a natural circulation pattern as hot
air rises and moves into the living areas while cool air flows through
the bottom opening into the solar-heated space between the glass and
the concrete. During the summer, when additional heat is unwanted,
the top air passages are closed and the rising air is channeled outside.
This same approach has been successfully employed by Doug Kelbaugh in his passive solar house in Princeton, New Jersey.
In addition to such passive approaches, hundreds of active solar
heating systems have been built, using a variety of collectors and
storage systems. Each technology stresses certain features-good
performance, rugged durability, attractive appearance, or low costeach of which is often achieved at the sacrifice of others. The U.S.
effort has been by far the most expensive and ambitious, though important work has been done in the Soviet Union, Great Britain, Australia, Japan, Denmark, Egypt, and Israel.
Flat-plate solar collectors suffice for normal heating purposes. After
heat has been collected and then transported to storage reservoirs,
technologies
most active solar heating systems use conventional
(n~;;~rdradiators or forced-air ducts) to deliver it to the living areas as
Solar collectors are being used in diverse locations to heat buildings.
The town of Mejannes-le-Clap
in southern France has announced
15
16
plans to obtain most of its heat tram the sun. Several U.S. solarheated communities, as well as individual schools, meeting halls,
office buildings, and even hamburger stands, nre now under construction. Saudi Arabia plans to build a new town at Jubail, using
sunlight for heating, for cooling, and for running water pumps; the
Saudis are now also building the world’s largest solar-heated building
-a 325,000 square fooi athletic fieldhouse--in Tabuk.
Storing heat for a couple of days is not difficult; heated water or
gravel will do the job if 2 l>-ge insulated storage bin. is used. Eutectic
caI tc ,--I ‘_/ I -; :I).?: .;‘r - \” 3 prodigious amounts of heat when they
1_I : <,ttd>e i, : nen they re-solidify, can reduce the minimum storage v~3lume
ded by a factor of six. The most serious
pl(,hlrr;3< 17!.:;*;‘-:
.- storage of heat in phase-changing eutectic
Jalt~ nave bc,en overcome, according to Dr. Maria Telkes, a leading
American expert in solar thermal storage.17
In the 1940s, the Japanese built an energy storage system that
worked on an annual cycle. During cold months, heat was pumped
from a large container of water; by the end of the winter, a huge
block of ice had formed, into which excess building heat was cast
during the summer. The Japanese concept was recently revived by
Harry Fischer of the Oak Ridge National Laboratory in Tennessee.
Fischer found that when combined with a solar collector, a radiator,
and an efficient heat pump, such an annual storage system can perform admirably over a wide range of climates. Fischer’s prototype
worked so well hat several private companies decided to develop the
concept further.18
Many simple solar technologies can be used to cool buildings. Simple
ceiling vents may suffice to expel hot air, at the same time drawing
cooler air up from a basement or well. In dry climates, evaporative
coolers can be used to chill the air. In .more humid areas, solar-absorption air conditioners may be needed. The logical successors to
contemporary cooling units, solar air conditioners are currently being
developed in Japan and the United States. While early solar air
conditioners required heat at about 120” C for optimum performance,
a Japanese company has developed a unit that operates satisfactorily
.--
“The day is dawning when heating
and cooling self-sufficiency will be an
economical option for most new
buildings.”
at 75" C-a temperature any commercial solar collector can easily
muster. Fortuitously, solar air conditioners reach peak cooling capacity when the sun burns brightest, which is when they are most
needed. Consequently, solar air conditioners could reduce peak demands .I~ many electrical power grids. As cost-effective solar air conditioners reach the market, the overall economics of solar systems will
improve be< ?IJ~C the collectors will begin providing a year-round
1.
tienelf:r I+
It is harder in temperate than in tropical regions to provide with solar
technologies 100 percent of the heat buildings need. It is generally
cheaper at present to et supplementary heat during long cloudy periods from conventiona B fuels, wind power, biogas, or wood. However,
when solar equipment is mass-produced, prices should plummet,
while fossil fuel prices can only climb. Moreover, major improvements
in the design of collectors, thermal storage systems, and heat-transfer
mechanisms are being made. Indeed, the day is dawning when heating and cooling self-sufficiency will be an economical option for most
new buildings.
Solar heating systems are most attractive when considered in terms of
“lifetime costs”; the initial investment p/us the lifetime operating
costs of solar systems often total less than the combined purchase
and operating costs of conventional heating systems. For example,
recent U.S. studies have shown solar heating to be more economical
than electrical heating except in competition with cheap hydropower.20
Investments in solar technologies can be mortgaged at a steady cost
over the years, while the fuel costs of alternative systems will rise at
least as fast as general inflation. In fact, the initial cost alone of solar
heating systems often amounts to less than the initial cost of electrical resistance heating, if the cost of the building’s share of a new
power plant and the electrical distribution system is included. However, the cost of a solar heating system must be borne entirely by the
homeowner, while a utility builds the power plant and strings the
power lines. The utility borrows money at a lower interest rate than
the homeowner can obtain, and it averages the cost of electricity from
the expensive new plant with that of power from cheap plants built
decades earlier so that true marginal costs are never compared.z*
18
Solar heated buildings are now commercially viable. However, largescale changes in the housing industry are not accomplished easilywitness the 30,000 autonomous building code jurisdictions
in the
United States. The building industry is localized-even the giant construction firms each produce fewer than one-half of one percent of
all units. Profit margins are small, and salability has traditionaily
reflected the builder’s ability to keep purchase prices low. Nonetheless, a respected market research organization, Frost and Sullivan,
predicts that 2.5 million U.S. residences will be solar heated and
cooled by 1985, and the American Institute of Architects has urged
an even more ambitious solar development program.22
Solar heating becomes even more attractive when it is crossbred with
other compatible technologies. Its happy marriage to absorption airconditioners and heat pumps has already been mentioned. Greenhouses too can be splendid solar collectors, producing much more
heat than they need in even the dead of winter, if they are tightly
constructed, well insulated, and fitted with substantial thermal storage capacity. Whereas many old-style attached greenhouses placed
demands on the heating system of the main house, inexpensive solar
greenhouses can actually furnish heat to the living area while they
extend the growing season for home-grown vegetables. A program to
build greenhouses for low-income families in northern New Mexico
out of local materials, low-cost fiberglass, and polyethylene has already proven successful.
In addition to warming buildings, low-grade heat from simple solar
devices can also be used to dry crops-a task that now often consumes prodigious amounts of propane and methane gas. Solar dryers
are now being used to remove moisture from lumber and textiles, as
well as from corn, soybeans, alfalfa, raisins, and prunes. The sun has
always been used to dry mcc;t of the world’s laundry.
For more than a century, solar advocates have gathered crowds by
cooking food with devices that use mirrors to intensify sunlight.
Now that firewood sup lies are growing scarce in many parts of the
Third World, solar coo kping is being taken more seriously. Althou h
solar cookers proved popular in some village experiments in ta e
1960s, their high cost, as much as $25 each, prohibited widespread
use. Today, however, cheap new reflecting materials like aluminized
mylar can be stretched over inexpensive locally-made frames. In poor
countries, solar cookers will be only supplementary devices for now,
since these mechanisms cannot function at night or in cloudy weather
and since storing high- temperature heat is expensive. But if heat
storage technology advances, solar stoves and ovens may play an increasingly important role in rich and poor countries alike.
Solar technology now also encompasses desalination devices that
evaporate water to separate it from salt. In the late 19th century, a
huge solar desalination plant near Salinas, Chile, provided up to
6,000 gallons of fresh water per day for a nitrate mine. Recent research has led to major improvements in the technology of solar
desalination, especially to improvements in “multiple-effect”
solar
stills. Today, this sun-driven process holds great promise, especially
in the Middle East and other arid regions. A small Soviet solar desalination plant in the Kyzyl Kum Desert in central Asia now produces four tons of fresh water a day.23
Relatively low temperature sources of heat can
erate pumps and engines. In the 186Os, Augustin
physicist, developed a one-half horsepower solar
early 20th century, more efficient en ines were
or ether instead of water as the wor a ing fluid.
man constructed a So-horsepower solar engine
irrigation water from the Nile.
also be used to opMouchot, a French
steam engine. In the
built using ammonia
In 1912, Frank Shunear Cairo to pump
Scores of solar devices were built around the world in the early decades of this century, but none withstood the economic competition of
low-cost fossil fuels. In recent years, with fuel prices soaring, solar
pumps have begun to attract attention again. In 1975, a JO-horsepower solar pump of French design was installed in San Luis de la
Paz to meet this Mexican town’s irrigation and drinking needs. Mexico has ordered ten more such pumps; and Senegal, Niger, and Maur-
19
20
itania have installed similar devices. At resent, solar pumps make
economic sense only in remote areas w Kere fuel and maintenance
costs for conventional systems are extremely high. But, many authorities believe, the costs of solar pumps could be dramatically reduced
by taking advanta e of the findings of further research and the economies of mass pro f uction.24
Solar energy can be used directly in various industrial processes. A
study of the Australian food-processing industry found, for example,
that heat comprised 90 ercent of the industry’s energy needs; almost
all this heat was at un crer 150" C, and 80 percent was below 100" C.
Such low-temperature heat can be easily produced and stored using
elementary solar technologies. Similarly, a study of an Australian
soft-drink plant found that enough collectors could be retrofitted
onto the factory’s roof to provide 70 percent of all the plant’s heat
requirements.25
recent study of U.S. industrial heating demands concludes that
about 7.5 percent of all heat is used at temperatures below 100°C and
28 percent below 288°C. However, direct solar power can be used to
pre- hea t materials from ambient temperatures to intermediate temperatures before another energy source is employed to achieve the still
higher temperature demanded for an industrial process. Such solar
pre-heating can play a role in virtually every industrial heat application. If pre-heating is used, 27 percent of all energy for U.S. industrial heat can be delivered under 100" C and about 52 percent under
A
288" c.26
Much of the energy used in the residential, commercial, agricultural,
and industrial sectors is employed as low-temperature heat. In the recent past, this demand has been filled by burning fossil fuels at thousands of degrees or nuclear fuels at millions of degrees. Because such
energy sources were comparatively cheap, little thought was given to
the thermodynamic inefficiency of using them to produce low-grade
heat. Now that fuel costs are mounting rapidly, however, demands
for heat increasingly will be met directly from the sun.
“A sensible energy strategy demands
more than the simple-minded substitution
of sunlight for uranium.”
Electricity from the Sun
It was long believed that nuclear power would replace the fossil fuels.
Because nuclear power is best utilized in centralized electrical power
plants, virtually all energy projections therefore show electricity ful.filling a growing fraction of all projected energy demands. Some
solar proponents advocate large centralized solar power plants as
direct replacements for nuclear power plants to meet this demand.
However, solar technologies can provide energy of any quality, and
remarkably little of the world’s work requires electricity. A sensible
energy strategy demands more than the simple-minded substitution of
sunlight for uranium.27
Electricity now comprises less than 20 percent of energy use in virtually all countries. If energy sources were carefully matched with energy uses, it is difficult to imagine a future society that would I-PQ~
more than one-tenth of its energy budget as e!Pct:iiiiy-the
.highest
quality and most expensive form of energy. Today, only 11 percent
of U.S. energy is used as electricity, and much of this need could be
met with other energy sources. To fill genuine needs for electricity,
the most attractive technology in many parts of the world will be
direct solar conversion,
Two types of large, land-based solar thermal power plants are rcceiving widespread attention. The “power tower” is currently attracting
the most money and minds, although a rival concept-the
“solar
farm” -is also being investigated. The power tower relies u on a large
field of mirrors to focus sunlight on a boiler located on a Righ structure- the “tower.” The mirrors are adjusted to follow the sun across
the sky, always maintaining an angle that reflects sunlight back to
the boiler. The boiler, in turn, produces high pressure steam to run a
turbine to generate electricity. The French, who successfully fed
electricity into their national grid from a small tower prototype in
January of 1977, plan to have a lo-megawatt unit operating by 1981
and have been a gressively tr ing to interest the desert nations of the
Middle East in t1 is effort. T h e United States is now testing a small
prototype involving a N-acre mirror field and a ZOO-watt tower in
21
99
“”
New Mexico, and it plans to put a lo-megawatt
operation by 1980 at Barstow, California.
power plan t into
An electric utility in New Mexico plans to combine three 430-foot
power towers that generate a total of 50 megawatts with an existing
gas-fired power plant at Albuquerque. The proposed complex would
utilize the existing generators, turbines, condensers, switchyard
etc.
The resulting hybrid, which would cost $60 million and cover 170
acres, would have no heat storage capacity; it would simply heat its
boilers with gas when the sun failed to shine. A survey by the utility
identified 600 existing power plants in the American Southwest (with
about 40,000 megawatts of electrical generating capacity) that could
be retrofitted with solar power towers.
The “solar farm” concept would employ rows of parabolic reflectors
to direct concentrated sunlight onto pipes containing molten salts
or hot gases. Special heat exchangers would transfer the 600" C heat
from the pipes to storage tanks, filled with melted metal, from whence
it could be drawn to generate high pressure steam to run a turbine.
Both the solar farm and the power tower approaches require direct
sunlight because their concentrating mirrors cannot use diffuse light.
Both will also probably be feasible only in semi-arid regions with
few cloudy days and little pollution. One objection raised to such
facilities is that they would despoil large tracts of pristine desert.
However, proponents point out that the area needed to produce 1,000
megawatts of solar electricity is less than the amount of land that
would have to be strip-mined to provide fuel for a similar sized coal
plant during its SO-year lifetime and that the solar plant’s land could
be used forever. In fact, according to Aden and Marjorie Meinel, a
l,OOO-megawatt solar farm on the Arizona desert would require no
more land than must, for safety reasons, be deeded for a nuclear reactor of the same capacity.28
Large, centralized solar electric plants consume no finite fuels, produce no nuciear explosives, and hold no ecological punches. With
development, such plants should also be economically competitive
with fossil-fueled, fission, and fusion power plants. However, they
reduce only electrici
and they are subject to all the problems inrlneeds
erent in centralized x igh technologies. To the extent that energy
can be met with lower quality sources or decentralized equipment, the centralized options should be avoided.
As a power source in countries where land is scarce or where cloud
cover is frequent, solar electric plants are less promising; efficient
long-distance cryogenic electrical transmission may prove feasible
but will probably be extremely expensive. Proposals to tap North
African deserts for power for Western Europe or to course Mexican
sunlight through New York’s power grid are therefore unlikely to
bear fruit. A more likely consequence of solar thermal-electric development would be the relocation of many ener y-intensive industries
in sunny climes. In fact, Professor Ignacy Saca s, director of the International Center for Research on Environment and Development
in Paris, has predicted that a new solar-powered industrial civilization will emerge in the tropics.
Land-based solar electric plants must bow to one incontrovertible
fact: it is always night over half the earth. If such facilities are to
generate power after the sun sets, oversized collectors must be built
and the excess heat retained in an expensive storage facility until it
is needed. But ocean thermal electric conversion (OTEC) plants,
which use the ocean as a free collector and storage system, are unaffected by daily cycles. Because the ocean’s temperature varies little,
OTEC plants can be a source of steady, round-the-clock power.
The temperature difference between the warm surface waters of tropical oceans and the colder waters in the depths is about 20" C. In
1881, J. D’Arsonval
su gested in an article in Revue Scientifique
that this difference coul f be used to run a closed-cycle engine. In the
192Os, another French scientist, Georges Claude, persuaded the
French government to build a number of open-cycle power plants to
exploit these ocean thermal gradients. After World War II, the French
Government built several OTEC plants (the largest of whicli had a
capacity of 7.5 megawatts) in the hope that such plants would provide inexpensive energy to France’s tropical colonies. French interest
23
24
in the project crumbled along with its overseas empire, but the idea
of harnessing ocean thermal gradients to generate power lingers on.29
Because of the small temperature differences between deep and surface waters, OTEC’s potential efficiency is severely limited. Moreover, as much as a third of the power an OTEC facility produces
may be required to pump the enormous amounts of water needed to
drive the cycle. Despite these difficulties and the additional problem
of transporting power to users on the shore, OTEC proponents contend that the system will be cheap enough to underprice competing
sources of electricity. However, this contention is untested, and
estimates of an OTEC unit’s cost range from about $450 to almost
$4,000 per installed kilowatt-excluding
the costs of transporting the
electricity to the land and the costs of any environmental damages.
The real cost will probably fall between these extremes, but early
models, at least, will likely veer toward :he high end.3o
The OTEC concept does not involve any new basic technology. Its
proponents tend to downplay the technical difficulties
as simply
matters of “good plumbing,” even though the system would require
pumps and heat exchangers far larger than any in existence. Because
they do not consume any fuel, OTEC systems are largely insured
against future cost increases that could affect nuclear or fossilfueled plants. On the other hand, with so many of their costs as,
literally, sunk investments, the viability of OTECs will depend entirely upon their durability and reliability-two
open questions at this
point. Unexpected vulnerabilities
to corrosion, biolcJca1 fouling,
hurricanes, or various other plagues could drive costs up dramatically.
Intensive deployment on the scale urged by OTEC’s most ardent advocates could also possibly engender a variety of environmental
problems that a few scattered plants would not provoke. An increase
in the overall heat of substantial bodies of water and the upwelling
of nutrient-rich
waters from the ocean bottom could both bring on
unfortunate consequences. Ocean temperature shifts could have farreaching impacts on weather and climate, and displacing deep waters
would disturb marine ecology. In addition, physicist Robert Williams
of Princeton calculates, the upwelling of carbon-rich water from the
ocean bottom could cause atmospheric carbon dioxide to increase
substantially .31 OTECs, like other large centralized sources of electricity, have costs that multiply rapidly when large numbers of plants
are built. This technology should probably be limited to a modest
number of facilities in ocean areas where conditions are optimal.
The most exciting solar electric prospect is the photovoltaic cell-now
the principal power source of space satellites. Such cells generate
electricity directly when sunlight falls on them. They have no moving
parts, consume no fuel, produce no pollution, operate at environmental temperatures, have long lifetimes, require little maintenance,
and can be fashioned from silicon, the second most abundant element
in the Earth’s crust.32
Photovoltaic cells are modular by nature, and little is to be gained by
grouping large masses of cells at a single collection site. On the contrary, the technology is most sensibly applied in a decentralized
fashion-perhaps
incorporated in the roofs of buildings-so
that
transmission and storage problems can be minimized. With decentralized use, the 80 ercent or more of the sunlight that such tel.;
do not convert into ePectricity can be harnessed to provide energy for
space heating and cooling, water heating, and refrigeration.
Fundamental physical constraints limit the theoretical efficiency of
phntovoltaic cells to under 25 percent. Numerous practical problems
force the real efficiency lower-for silicon photovoltaics, the efficiency
ceiling is about 20 percent. To obtain miiximiim efficiency, reiativeiy
pure materials with regular crystal structures are required. Such
near-perfection is difficult and expensive to obtain. High costs have,
in fact, been the principal deterrent to widespread use of photovoltaic cells.
Cost comparisons between photovoltaic systems and conventional
sy! ‘ems can be corn licated. Solar cells produce electricity only when
the sun shines, whi Pe conventional power plants are forced to shut
down frequently
for repairs or maintenance. Depending on the
amount of sunlight available where a photovoltaic array is located,
25
26
the cells might produce between one-fourth and one-half as much
power per kilowatt of installed capacity as an average nuclear power
plant does. Adding to the costs of photovoltaics is the need for some
kind of storage system; on the other hand, the use of photovoltaics
may eliminate the need for expensive transmission and distribution
systems.
Depending upon who does the figuring, photovoltaic cells now cost
between 20 and 40 times as much as conventional sources of baseload electricity. However, as a source of power just during daylight
periods of peak demand, photovoltaics cost only four to five times as
much as conventional power plants plus distribution systems. Moreover, the costs of conventional power plants have shot steadily upward in recent years while the costs of photovoltaic cells have rapidly
declined, and several new approaches are being pursued in an effort
to further diminish the costs of photovoltaic arrays. For example,
focusing collectors that use inexpensive lenses or mirrors to gather
sunlight from a broad area and concentrate it on the cells are being
employed. The Winston collector can obtain an eight-to-one concentration ratio without tracking the sun; “tracking”
collectors can
obtain much higher multiples, but at far greater expense.33
Another approach to cutting the costs of photovoltaic cells has been
to use less efficient but much cheaper materials than those usually
used; amorphous silicon and combinations of cadmium sulfide and
copper sulfide are strong candidates. Although the required collector
area is thus increased, total costs may be less. Conversely, another
approach has been to improve the processing of high-grade materials
for photovoltaic cells. Currently, each cell is handcrafted by artisans
who use techniques not unlike those employed in a Swiss watch factory. Simple mechanization of this process could lead to large savings. The costs of photovoltaic cells, which amounted to $200,000
per peak kilowatt in ~959, have already fallen to about $13,000 per
peak kilowatt and most experts believe that prices will continue to
fall rapidly.34
Increased production is of paramount
prices of photovoltaics. In an 18-month
importance in lowering the
period of 1975-76, U.S. pur-
chases of photovoltaic cells for earth-bound purposes doubled and
the average price per cell dropped by about 50 percent. Price reductions of from 10 to 30 percent for each doubling of output have been
common in the electrical components industries, and photovoltaic
production should prove no exception to the rule.
The objective of the Low-Cost Silicon Array Project of the U.S. Energy Research and Development Administration
is to produce photovoltaics for less than $500 per peak kilowatt, and to produce more
than 500 megawatts annually by 1985. This program, contracted
through the California Institute of Technology, involves a large
A general consensus appears to
number of major corporations.
be developing among the participants that the goals are reachable
and may even be far too modest. Under the auspices of the government’s “Project Sunshine,” Japan has undertaken a similar research
effort.35
From a “net energy” perspective, photovoltaics are appealing. Detailed studies of the energy needed to manufacture such cells shows
that the energy debt can be paid in less than two years of operation.
With more energy-efficient production processes, the energy payback
period could, theoretically, be reduced to a matter of weeks. If the
energy some cells produce is fed back to produce more cells, photovoltaics can become true energy “breeders’‘-making
more and more
energy available each year without consuming any nonrenewable resources. In fact, Malcolm Slesser and Ian Hounam have calculated,
an initial one-megawatt investment in photovoltaic cells with a twoyear payback period could multiply in 40 years to provide 90 percent
of the world’s energy needs. These calculations may be a bit optimistic, and the world does not want or need to consume 90 percent
of its energy in the form of electricity; but photovoltaics, like other
solar technologies, hold up well under net-energy analysis.36
A variety of options are available to produce electricity directly from
the sun. Several of the approaches sketched here-all of which have
been technically demonstrated-are
now economically competitive
with fossil-fueled plants under some conditions. Prices can be reasonably expected to fall dramatically as more experience is gained. Al-
27
though solar electricity will probably never be really cheap, it is
doubtless worth payin some economic premium for a source of electricity that is safe, f ependable, renewable, non-polluting,
and-in
the case of photovoltaics-highly
decentralized.37
Catching the Wind
The air that envelopes the Earth functions as a XLbillion-cubic-kilometer storage battery for solar energy. Winds are generated by the
uneven heating of our spinning planet’s land and water, plains and
mountains, equatorial regions and poles. The idea of harnessing this
wind to serve human needs may have first occurred to someone
watching a leaf skitter across a pond. Five thousand years ago, the
Egyptians were already sailing barges along the Nile. Wind-powered
vessels of one sort or another dominated shipping until the Nineteenth century, when ships driven by fossil fuels gradually eased
them out. A few large cargo schooners plied the waters off the U.S.
Atlantic Coast until the 1930s, and the largest windjammers were the
greatest wind machines the world has known.38
The windmill appears to have originated in Persia two millenia ago.
There, vertical shaft devices that turned like merry-go-rounds
were
used to grind grain and pump water. After the Arab conquest of
Persia, wind power spread with Islam throughout the Middle East and
to the southern Mediterranean lands. Invading Mongols carried the
windmill back to China. Returning crusaders likewise appear to have
transferred the technology to Europe-though
the tilt (30 degrees to
the horizontal) of the axes of early European mills have led some
scientists to believe that the device may have been invented independently by a European. Eventually, horizontal-axis windmills with
blades that turned like ferris wheels were developed, and they spread
throughout Europe.39
By the 17th century, the Dutch had a commanding lead in wind technology and were already using wind power to saw wood and make
paper. In the late 19th century the mantle of’ leadership passed to the
“It is doubtless worth paying some
economic premium for a source of
electricity that is safe, dependable,
renewable, and non-polluting.”
Danes, who had about 100,000 windmills in operation by 1900. Under the leadership of Poul la Cour, Denmark began making significant investments in wind- enerated electricity and by 1916 was operating more than 1,300 win f generators.
The windmill played an important role in American history, especially
in the Great Plains, where it was used to pump water. More than six
million windmills were built in the United States over the last century; about 150,000 still spin productively.
Prior to the large-scale
federal commitment to rural electrification in the 1930s and 1940s,
windmills supplied much of rural America with its only source of
electricity.
After World War I, cheap hydropower and dependable fossil fuels
underpriced wind power plants. However, research in many parts of
the world continued, and many interesting windmill prototypes were
constructed. In 1931, the Soviet Union built the world’s first large
wind generator near Yalta. Overlooking the Black Sea, this loo-kilowatt turbine produced about 280,000
kilowatt-hours
of electricity
per year. In the 195Os, Great Britain built two 100-kilowatt turbines.
In 19.~7, Denmark built a ZOO-kilowatt turbine, and France constructed an BOO-kilowatt wind generator. In 1963, a l,OOO-kilowatt wind
turbine was built in France.
The largest wind generator ever built was the 1,250-kilowatt Grandpa’s Knob machine designed by Palmer Putnam and erected on a
mountain top in central Vermont. It began generating electricity on
August 29, 1941, just two years after its conception. However, the
manufacturer had been forced to cut corners in his haste to finish
construction before the icy hand of war-time rationing closed upon
the project, and the eight-ton propeller blades developed stress cracks
around their rivet holes. Although the cracking was noticed early,
the blades could not be replaced because of materials shortages. Finally, a blade split, spun 750 feet in the air, and brought the experiment to a crashing conclusion. The private manufacturer had invested more than one million dollars in the project and could afford to risk
no more.40
30
Despite the enthusiasm of occasional wind-power champions in the
federal government, no more major wind generators were constructed
in the United States until 1975. Then, NASA began operating a lOOkilowatt prototype near Sandusky, Ohio, that resembles a huge helicopter mounted sideways atop a transmission tower. The next major
step in the American program will be a 1,5OO-kilowatt wind turbine
to be built jointly by General Electric and United Technology Corporation by 1978.
Before the GE-UTC turbine begins operating, however, it may have
slipped into second place in the size sweepstakes. Tvind, a Danish
college, has nearly completed a 2,OOO-kilowatt wind turbine, at a cost
of only $350,000.
(Doubtless the most important factor in holding
down expenses for the Tvind generator is that the college staff paid
for the project out of their own pockets. If successful, Tvind will
hearten those who hope that major technical accomplishments can
still be achieved without reliance on central governments or big business.)41
The Tvind wind machine, like virtually all large wind turbines today,
will have only two blades. While more blades provide more torque
in low-speed winds (making multiple blades particularly useful for
purposes such as small-scale water pumping), fewer blades capture
more energy for their cost in faster winds. A two-blade propeller can
extract most of the available energy from a large vertical area without
filling the area with metal that could crack or split in a storm.
Since power production increases with the square of a turbine’s size,
large wind machines produce far more energy than do small ones.
Moreover, wind power increases as the cube of velocity, so a lo-meterper-second wind produces eight times as much power as a s-meterper-second breeze does. Consequently, some wind power enthusiasts
limit their dreams to huge turbines on very windy sites. In particular, a
recent survey of large U.S. corporations conducting wind power research disclosed that only one company had any interest in small or
intermediate sized turbines.42
However, the “think big” approach does not necessarily make sense.
The crucial question for windmills is how much energy is harnessed
per dollar of investment. Increases in output are desirable only if
the value of the additional energy extracted exceeds the extra cost,
and economic optimization does not necessarily lead to the construction of giant turbines. Smaller windmills might lend themselves more
easily to mass production and might be easier to locate close to the
end-user (thus reducing transmission costs). Small windmills
can
produce power in much lower winds than large ones do and can thus
operate more over a given time. Smaller-scale equipment also allows a
greater decentralization of ownership and control, and the consequences of equipment failure are not likely to be catastrophic. Finally,
wind turbine development will probably be constrained by practical
limits on propeller size. Large turbines place great stresses on both
the blade and tower, and all giant turbines built to date have suffered
from metal fatigue.
On a small scale, wind power can be cheaply harnessed to perform
many kinds of work. The Valley of Lasithi on Crete uses an estimated 10,000 windmills, which catch the wind in triangular bands of
white sail cloth, to pump irrigation water. Similar windmills built of
local materials have recently been erected in East Africa. The New
Alchemy Institute in Massachusetts, working with the Indian Institute of Agricultural
Research and the Indian National Aeronautical
Laboratory, has developed a 25-foot sailwing pump for rural use;
employing the wheel of a bullock cart as the hub and a bamboo frame
for the cloth sails, this simple machine could provide cheap power to
Indian villages. The Brace Research Institute in Canada has designed
a Savonius water pump that can be constructed from two 45-gallon
oil drums cut in half. Already used in the Caribbean, the device costs
about $50 to make and will operate at wind speeds as low as 8 mph.
Traditionally,
wind has been used primarily to pump water and to
grind grain. Windmills can also produce heat that can be stored and
used later in space heating, crop drying, or manufacturing processes.
A particularly attractive new approach is to compress air with wind
turbines. Pressurized air can be stored much more easily than electricity, a fact to which virtually every gasoline station in the United
31
32
States attests. Stored air can either be used as needed to directly power
mechanical equipment or released through a turbine to generate electricity. On a large scale, pressurized air can be stored in underground
caverns.
The modern wind enthusiast can choose from many options: multiple-blade propellers, triple-blade props, double-blade props, singleblade versions with counterweights,
sailwings, cross-wind paddles,
and gyromills. In some wind turbines, the propeller is upwind from
the platform, while in others it is located downwind. Some platforms
support single large turbines; others support many small ones. A
machine with two sets of blades turning in opposite directions is
being tested in West Germany.43
One of the most interesting multiple-blade
devices for small and
moderate sized generators is under development at Oklahoma State
University. This mill resembles a hu e bicycle tire, with flat aluminum
blades radiating from the hub li &e so many spokes. Instead of
gearing the generator to the hub of the windmill,
the Oklahoma
State machine operates on the principle of the spinning wheel: the
generator is connected to a belt that encircles the faster-moving outer
rim.
The Darrieus wind generator, favored by the National Research
Council of Canada and by Sandia Laboratories in New Mexico, looks
like an upside-down egg beater, and turns around its vertical axis like
a spinning coin. The Darrieus holds several striking advantages over
horizontal axis turbines: it will rotate regardless of wind direction;
it does not require blade adjustments for different wind speeds; and it
can operate without an expensive tower to provide rotor clearance
from the ground. Aerodynamically
efficient and light-weight,
the
Darrieus might cost as little as one-sixth as much as a horizontalshaft windmill of the same capacity. In early 1977, a ZOO-kilowatt
Canadian Darrieus wind turbine began feeding electricity into the
24,000-kilowatt
power grid that serves the Magdalen Islands in the
Gulf of St. Lawrence. If this machine lives up to its economic potential, other Darrieus turbines will be installed.d4
intriguing
new ap roaches to wind power may well be gestating.
Little money or ef Port has been put into wind turbine research over
the last two decades, although aeronautical engineering has made
enormous strides over the same period. With interest in wind machines gathering force, new approaches could soon emerge. For example, a “confined vortex” generator being developed by James Yen
steers wind through a circular tower, creating a small tornado-like
effect; this generator utilizes the difference in pressure between the
center of the swirling wind and the outside air to drive a turbine.45
Large amounts of electricity could, theoretically, be generated by
relatively small turbines of this type. The U.S. Energy Research and
Development Administration
recently awarded Dr. Yen $200,000 to
develop this idea further. However, the viability of wind power does
not depend upon scientific breakthroughs;
existing wind technologies can compete on their own terms for a substantial share of the
world’s future energy budget.
Estimating the probable cost of wind power is a somewhat speculative undertaking. The cost of generating electricity with the wind
can be measured in two different ways-depending
upon whether the
sys tern provides “base load” power or only supplementary power. If
wind generators feed power directly into a grid when the wind blows,
and if other generating facilities have to be constructed to handle
peak loads when the wind isn’t blowing, the average costs of building
and maintaining such windmills must compete with merely the cost of
fuel for the “alternative potver plant. Obviously,
this calculation
hinges not only on how much a windmill costs to construct, but also
on how long it lasts and how reliably it functions. Conclusions are
premature until experience has been gained, but many studies have
suggested that intermittent electricity could be generated today from
the wind for considerably less than the cost of providing fuel for an
existing oil-fired unit. Moreover, wind power costs could diminish
significantly as more experience is acquired, while oil costs will certainly rise.46
If wind is to be used to provide constant, reliable power, then the cost
of building a wind generator plus a storage facility must not exceed
the total cost (including the environmental cost) of building and
33
34
operating a conventional power plant. Used in conjunction with a
hydro-electric facility with reserve ,capacity, wind turbines should
already have a substantial cost advantage over conventional power
plants. For other storage set-ups, cost calculations remain unsubstantiated, but studies of analogous technologies suggest that such
base-load wind systems will be economically sound. When social and
environmental costs are included, the case becomes even stronger.
Accordingly, such systems should now be built and operated so that
these calculations can be proven.
The rate and extent to which wind power is put to work is much
more likely to be a function of political considerations than of technical or economic limits. The World Meteorological Organization has
estimated that 20 million megawatts of wind power can be commercially tapped at the choicest sites around the world, not including
the possible contributions from large clusters of windmills at sea.47
By comparison, the current total world electrical generating capacity
is about one-and-one-half
million megawatts. Even allowing for the
intermittent nature of the resource, wind availability will not limit
wind power development. Long before a large fraction of the wind’s
power is reaped, capital constraints and social objections will impose
limits on the growth of wind power.
Well-designed, well-placed wind turbines will achieve a high net energy output with an exceptionally mild environmental and climatic
impact: wind machines produce no pollution, no hazardous materials, and little noise. In fact, the principal environmental consequences
of wind power will be the comparatively modest ones associated with
mining and refining the metals needed for wind turbine construction
-ill effects associated with virtually every energy source. Windmills
will have to be kept out of the migratory flyways of birds, but these
routes are well-known
and can be easily avoided. Where aesthetic
objections to the use of wind technology arise, windmills could be
located out of the visual range of populated areas, even a few miles
out to sea. Moreover, some wind machines, such as the Darrieus,
strike many as handsome. All things considered, a cleaner, safer,
less disruptive source of energy is hard to imagine.48
“The rate 2nd extent to which wind
power is put to work is much more
likely to be a function of political
considerations than of technical or
economic limits.”
Falling Water
Numerous surveys of the world’s water-power resources suggest that
a potential of about three million megawatts exists, of which about
one-tenth is now developed. The figure is unrealistic, however, since
reaching the three-million-megawatt
potential would require flooding
fertile agricultural bottomlands and rich natural ecosystems. On the
other hand, none of the surveys include the world’s vast assortment
of small hydro-electric sites. By even the most conservative standards, potential hydropower developments definitely exceed one million megawatts, while current world hydro-electric capacity is only
340 thousand megawatts.
Industrialized regions contain about 30 percent of the world’s hydroelectric potential as measured by conventional criteria but produce
about 80 percent of all its hydro-electricity.
North America produces
about one-third, Europe just a little less, and the Soviet Union about
one-tenth. Japan, with only 1 percent of the world’s potential, produces over 6 percent of global hydro-electricity.
In contrast, Africa is
blessed with 22 percent of all hydro-electric potential, but produces
only 2 percent of all hydro-electricity-half
of which comes from the
Aswan High Dam in Egypt, the Akosombo Dam in Ghana, and the
Kariba Dam on the Zambesi River between Zambia and Rhodesia.
Asia (excluding Japan and the USSR) has 27 percent of the potential
resources, and currently generates about 12 percent of the world’s
hydro-electricity;
most of its potential lies in the streams that drain
the Tibetan Plateau, at sites far from existing energy markets. Latin
America, with about 20 percent of the world’s total water-power resources, contributes about 6 percent of the current world output.
Nine of the world’s 15 most powerful rivers are in Asia, three are in
South America, two are in North America, and one is in Africa.49
The amount of hydropower available in a body of moving water is
determined by the volume of water and by the distance the water falls.
A small amount of water dropping from a great height can produce
as much power as a large amount of water falling a shorter distance.
The Amazon carries five times as much water to the sea as does the
35
world’s second largest river, the Congo; but because of the more
favorable topography of its basin, the Congo has more hydro-electric
potential. In mountainous headwater areas, such as Nepal, where
relatively small volumes of water fall great distances, numerous
choice sites exist for stations of up to 100 megawatts each.50
Used by the Romans to grind grain, water wheels reached their highest pre-electric form. in the mid-1700s with the development of the
turbine wheel. The Versailles waterworks produced about 56 kilowatts of mechanical power in the 18th century. In 1882, the first
small hydro-electric facility began producing 125 kilowatts of electricity in Appleton, Wisconsin; and, by 1925, hydropower accounted
for 40 percent of the world’s electric power.. Although hydro-electric
capacity has since grown IS-fold, its share of the world’s electricity
market has fallen to about 23 percent.
Early hydro-electric development tended to involve small facilities in
mountainous regions. In the 1930s, emphasis shifted to major dams
and reservoirs in the middle and lower sections of rivers, such as the
Tennessee Valley dams in the United States and the Volga River dams
in the Soviet Union. The world now has 64 hydroplants with capacities of 1,000 megawatts or more each: the Soviet Union has 16, the
United States has 12, Canada has 11 (the U.S. and Canada share
another), and Brazil has 10.
The environmental and social problems associated with huge dams
and reservoirs far outweigh those surrounding small-scale installations or projects that use river diversion techniques. Moreover, the
increments by which small facilities boost a region’s power supply
are manageable. In contrast, a tripling or quadrupling of a power
supply in one fell swoop by a giant dam can lead to a desperate
search for energy-intensive
industries to purchase surplus power,
dramatically upsetting the politics and culture of an area.
Much of the extensive hydro-electric development in Japan, Switzerland, and Sweden has entailed use of comparatively small facilities,
and such small units hold continuing promise for developing countries. In late 1975, China reportedly had 60,000 small facilities that
together generated over two million kilowatts-about
20 percent of
China’s total h y d ro-electric capacity. The Chinese facilities are located
in sparse1 populated areas to which sending electricity from huge
centralize cy facilities would involve prohibitive
transmission costs.
Local workers build the small earth-filled or rock-filled dams that
provide substantial flood control and irrigation benefits as they bring
power to the people.5’
Nevertheless, building enormous facilities to capture as much power
as possible while taking advantage of the economies of large scale
is tempting. Although this approach has been used extensively and
rather successfullv in temperate zones, many of the remaining
prime locations a!e in the tropics, where troubles may arise. The
Congo, for example, with a flow of 40,000 cubic meters per second
and a drop of nearly 300 meters in the final 200 kilometers of its
journey to the ocean, hds an underdeveloped hydro-electric potential
of 30,000 megawatts. But experience in other warm areas indicates
that great care must be taken in exploiting such resources.
The Aswan High Darn provides a textbook case of the problems tha:
can encumber a major hydro-electric development in the tropics. So
trouble-ridden is Aswan that its costs largely offset its benefits. Although Aswan is a source of electricity, of flood and drought control,
and of irrigation, th c dam’s users and uses sometimes conflict. For
example, Aswan provides more than 50 percent of Egypt’s electrical
power, but its production is highly seasonal; during winter months,
the flow of water through the dam is severely diminished while irrigation canals are cleaned. This reduced flow, causes power generation to
drop from a designed capacity of 2,000 megawatts to a mere 700
megawatts. Furthermore, lack of money for an extensive transmission
grid has meant that electricity does not reach many of the IUI ~1 villages that had hoped to benefit from the project.
Aswan saved Egypt’s rice and cotton crops during the droughts in
northeastern Afrir.a in 1972 and 1973. Irrigation has increased food
production by bringing approximately 750,000 formerly barren acres
under cultivation, and by allowing farmers to plant multiple crops
on a million acres that had previously been harvested only once a
37
38
z
ear. These timely boosts have enabled Egy t’s food production to
eep pace, though just barely, with its rapi crly growing population.
On the other hand, the dam has halted the natural flow of nutrientrich silt, leaving downstream farmers to rely increasingly upon energy-intensive chemical fertilizers; and the newly irrigated areas are
so plagued by waterlogging and mounting soil salinity that a $30million drainage program is now needed. In addition, the canals in
some areas rapidly clog with fast-growing water hyacinths.
The Aswan has also given a new lease to an age-old health hazard
in Egypt. Schistosomiasis, a disease caused by parasitic worms carried by water snails, has long been endemic in the Nile delta where
most of Egypt’s population is concentrated, but in the past it was
rarely found in upstream areas. Since the construction of the large
dam, infestations of this chronic and debilitating affliction are also
common along the Nile and its irrigation capillaries in Upper Egypt.
Many of the major problems associated with Aswan should have
been anticipated and avoided. Even now, Aswan’s worst problems
probably can be either solved or managed. But after-the-fact remedies
will be costlier and less effective than a modest preventative effort
would have been.
The inevitable siltation of reservoirs does more to spoil the use of
dams as renewable energy sources than does any other problem. Siltation is a corn lex phenomenon that hinges upon several factors, one
of which is t Re size of the reservoir. For example, the Tarbela Reservoir in Pakistan holds only about one-seventh the annual flow of
the Indus, while Lake Mead on the Colorado can retain two years’
flow. The life expectancy of the Tarbela is measurable in decades;
Lake Mead will last for centuries. The rate of natural erosion, another factor in siltation, is determined primarily by the local terrain.
Some large dams in stable terrains have a life expectancy of thousands of years; others have been known to lose virtually their entire
storage capacity during one bad storm. Logging and farming can
greatly accelerate natural erosion too; many reservoirs will fill with
silt during one-fourth their expected life spans because these and
other human activities ruin their watersheds.
“The greatest potential for future
hydropower development lies in
those lands that are currently most
starved for energy.”
Siltation, which affects the dam’s storage capacity but not its power
generating capacity, can be minimized. Water can be sluiced periodically through gates in the dam, carrying with it some of the accumulated silt. Reservoirs can be dredged, though at astronomical costs. By
far the most effective techni ue for handling siltation is lowering the
t rough reforestation projects and enrate of upstream erosion %
lightened land use.52
Dams cannot be evaluated apart from their interaction with many
other natural and artificial systems. They are just one component,
albeit a vital one, of river basin management. Locks will have to be
provided on navigable rivers, and fish ladders (one of the earliest victories of environmentalists)
must be installed where dams block the
spawning routes of anadromous fish. If a dam is located in a dry
area, power eneration must be coordinated with downstream irrigation needs. I f a populated basin is to be flooded, the many needs of
displaced people as well as the loss of fertile bottomland must be
taken into account. Unpopulated basins are politically easier to dam,
but in unsettled areas care must nevertheless be taken to preserve
unique ecosystems and other irreplaceable resources.
Dams are vulnerable to natural forces, human error, and acts of war.
The 1976 colla ses of the Bolan Dam in Pakistan, the Teton Dam in
Idaho, and a Parge earthen dam outside La Paz on Mexico’s Baja
Peninsula serve as em hatic reminders of the need for careful geological studies and the hig E:est standards of construction.
Dams recommend themselves over most other energy sources. They
provide many benefits unconnected to power production; they are
clean; and their use does not entail the storage problems that plague
so many other renewable sources. Indeed, using dams as storage
mechanisms may be the most effective way to fill in the gaps left by
solar and wind power. In addition, the conversion of water power
into electrical power is highly efficient-85
percent or more. Finally,
dams can be instruments of economic equity; the greatest potential
for future hydropower development lies in those lands that are currently most starved for energy.
39
Plant Power
Green plants began collecting and storing sunshine more than two
billion years ago. They photosynthesize an estimated one-tenth of
one percent of all solar energy that strikes the earth. Somewhat more
than half of this fraction is spent on plant metabolism; the remainder
is stored in chemical bonds and can be put to work by human beings.
All fossil fuels were once biomass, and the prospect of dramatically
shortening the time geological forces take to convert vegetation into
oil, gas, and coal (roughly a third of a billion years) now intrigues
many thoughtful persons. Dry cellulose has an average energy content of about four kilocalories per gram-60 percent as much as bituminous coal, and the hydrocarbons produced by certain plants contain more energy than coal does. Biomass can be transformed directly
into substitutes for some of our most rapidly vanishing fuels.
Because green lants can be grown almost everywhere, they are not
very susceptib Pe to international
political pressures. Unlike fossil
fuels, botanical energy resources are renewable. In addition, biomass
operations involve few of the environmental drawbacks associated
with the large-scale use of coal and oil.
The ultimate magnitude of this energy resource has not been established. Measuring the earth’s total
hotosynthetic
capacity poses
difficulties,
and estimates vary consi crerably. Most experts peg the
energy content of all annual biomass production at between 15 and
20 times the amount humans currently get from commercial energy
sources, although other estimates range from 10 to 40 times.sj Using
all the vegetation that grows on Earth annually as fuel is unthinkable. But the energy that could reasonably be harvested from organic
sources each year probably exceeds the energy content of all the fossil
fuels currently consumed annually.
Two important caveats must be attached to this statement. The first
qualification
concerns conversion efficiency. Much of the energy
bound in biomass will be lost during its conversion to useful fuels.
These losses, however, need be no greater than those involved in converting coal into synthetic oil and gas. The second catch is geographical: the areas with the greatest biomass reduction are wet e uatorial
-not the temperate lands where Puel use is highest to 27ay. The
;ifi?%ogical
energy potential of the United States, calculated liberally, probably amounts to about one-fifth of current commercial energy use; in contrast, the potential in many tropical countries is much
higher than their current fuel consumption levels. However, many
equatorial nations will be hard-pressed to secure the capital and to
develop the technology needed to use their potential plant power.54
Organic fuels fall into two broad categories: waste from non-energy
processes (such as food and paper production) and crops grown
explicitly for their energy value. Since waste dis osal is unavoidable
and often costly, converting waste into fuels-t Ke first option-is
a
sensible alternative to using valuable land for garbage dumps. However, the task of waste collection and disposal usually falls to those
who cling to the bottom rungs of the economic and social ladder and,
until recently, waste seldom attracted either the interest of the welleducated or the investment dollars of the well-heeled. But change is
afoot, partly because solid waste is now often viewed as a source of
abundant high-grade fuel that is close to major energy markets.
\
The wastes easiest to tap for fuels may be those that come from food
production. Bagasse, the residue from sugar cane, has long been
used as fuel in most cane-growing regions. Corn stalks and spoiled
grain are being eyed as potential sources of energy in the American
Midwest. And India’s brightest hope for bringing commercial energy
to most of its 600,000 villages is pinned to a device that produces
methane from excrement and that leaves fertilizer as a residue.
Agricultural
residues-the
inedible, unharvested portions of food
crops-represent
the largest potential source of energy from waste.
But most plant residues are sparsely distributed, and some cannot be
spared: they are needed to feed livestock, retard erosion, and enrich
the soil. Yet, wisely used, field residues can guard the soil, provide
animal fodder, and serve as a fuel source.
41
Agricultural energy demands are highly seasonal, and usage peaks do
not always coincide with the periods during which residue-derived
energy is most plentiful. In agricultural systems still largely dependent upon draft animals, this problem is minimized: silage and hay
can easily be stored until needed. On mechanized farms, energy storage poses a somewhat more difficult problem.
Animal excrement is another potentially valuable source of energy.
Much undigested energy remains bound in animal excrement: and
cattle feedlots, chicken coo s, and pig sties could easily become energy farms. Indeed, animal cpung has been burned in some parts of the
world for centuries; in the United States, buffalo chips once provided
cooking fuel to frontiersmen on the treeless Great Plains. In India
today, about 68 million tons of dry cow dung are burred as fuel each
year, mostly in rural areas, although more than 90 percent of the
potential heat and virtually all the nutrients in excrement are lost in
inefficient burning $55Far more work could be obtained from dung if
it were first digested to produce methane gas; moreover, all the nu’trients originally in the dung could then be returned to the soil as fertilizer .56
In May 1976, Calorific Recovery Anaerobic Process Inc., (CRAP),
of Oklahoma City received Federal Power Commission authorization
to provide the Natural Gas Pipeline Company annually with 820
million cubic feet of methane derived from feedlot wastes. Other similar proposals are being advanced. Although most commercial biogas
plants planned in the United States are associated with giant feedlots,
a more sensible long-term strategy might be to range-feed cattle as
long as possible and then to fatten them u , a thousand at a time, on
farms in the midwestern grain-belt. Cow cfung could power the farm
and provide surplus methane, and the residue could be used as fertilizer. In addition, methane generation has been found to be economically attractive in most dairies-an important point since more than
half of all U.S. cows are used for milk productions7
Collectible crop residues and feedlot wastes in the United States contain 4.6 quadrillion Btus (quads)-more energy than all the nation’s
farmers use. Generating methane from such residues is often eco-
nomical. However, developing a farm that is totally energy self-sufficient may require a broader goal than maximizing short-term food
output?
Human sewage, too, contains a large store of energy. In some rural
areas, particularly in China and India, ambitious programs to produce gaseous fuel from human and animal wastes are under way. Unfortunately,
toxic industrial effluents are now mixed with human
waste in many of the industrialized world’s sewage systems, and these
pollutants make clean energy-recovery vastly more difficult. If these
pollutants were kept separate, a large new energy source would become available.
The residues of the lumber and paper industries also contain usable
energy. A study conducted for the Ford Foundation’s Energy Policy
Project found that if the U.S. paper industry were to adopt the most
energy-efficient technologies now available and were to use its wood
wastes as fuel, fossil fuel consumption could be reduced by a staggering 75 percent. The Weyerhaeuser Company recently announced
a $75 million program to expand the use of wood waste as fuel for
its paper mills; “We’re getting out of oil and gas wherever we can,”
commented George Weyerhaeuser, the company’s president. Sweden
already obtains 7 percent of its total energy budget by exploiting
wastes of its huge forest-products industry.
Eventually, most paper becomes urban trash. Ideally, much of it
should instead be recycled-a process that would save trees, energy,
and money. But unrecycled paper, along with rotten vegetables, cotton rags, and other organic garbage, contains energy that can be economically recaptured. Milan, Italy runs its trolleys and electric
buses partly on power produced from trash. Baltimore, Maryland
expects to heat much of its downtown business district soon with
fuel obtained by distilling 1,000 tons of garbage a day.
American waste streams alone could, after conversion losses are subtracted, produce nearly five quads per year of methane and “charoil”
-about 7 percent of the current U.S. energy budget. Decentralized
43
agrarian societies could derive a far higher percentage of their commercial energy needs from agricultural, forest, and urban wastes.
The second plant-energy option, the production of “energy crops,”
will probably be limited to marginal lands, since worldwide population pressures are already relentlessly pushing food producers onto
lands ill-suited
to conventional
agriculture. Yet, much potential
energy cropland does exist in areas where food production cannot be
sustained. Some prime agricultural land could also be employed during the off-season to grow energy crops. For example, winter rye
(which has little forage value) could be planted in the American
Midwest after the fall corn harvest and harvested for energy in the
spring before maize is sowed.
Factors other than land scarcity limit biomass growth. The unavailability of nutrients and of an adequate water supply are two. Much
marginal land is exceedingly dry, and lumber and paper industries
will make large demands on areas wet enough to support trees. The
energy costs of irrigating arid lands can be enormous, reducing the
net energy output dramatically.
Yields from energy crops will ref!ect the amount of sunlight such
crops receive, the acreage devoted to collecting energy, and the efficiency with which sunlight is captured, stored, harvested, transported, and put to work. Ultimately, they will also depend upon our ability to produce crops that do not sap the land’s productivity and that
can resist common diseases, pests, fire, and harsh weather.
The most familiar energy crop, of course, is firewood. A good fuel
tree has a high annual yield when densely planted, resprouts from cut
stumps (coppices), thrives with only short rotation periods, and is
generally hardy. Favored species for fuel trees are eucalyptus, sycamore, and poplar-an
intelligently
planned tree plantation would
probably grow a mixture of species.
Forests canopy about one-tenth of the planet’s surface and represent
about half the earth’s captured biomass energy.59 A century ago,
the United States obtained three-fourths of its commercial energy
“Forwnopjut
one-fourth of the
planet’s sulfate ar&reppesent about half
the earth’s captured biomass energy.”
from wood. In the industrialized world today, only a small number of
the rural poor and a handful of self-styled rustics rely upon fuel
wood. However, the case is emphatically different in the Third World.
Thirty percent of India’s energy, and 96 percent of Tanzania’s comes
from wood.60 In all, about half the trees cut down around the world
are burned to cook food and to warm homes.
In many lands, unfortunately,
humans are propagating faster than
trees. Although much attention has been paid to the population-food
equation, scant notice has been given to the question of how the
growing numbers will cook their food. As desperate people clear the
land of mature trees and saplings alike, landscapes become barren;
and, where watersheds are stripped, increasingly severe flooding occurs. In the parched wastelands of north central Africa and the fragile
mountain environments of the Andes and the Himalayas, the worsening shortage of firewood is today’s most pressing energy crisis.bi
A variety of partial solutions have been suggested for the “firewood
crisis.” In southern Saudi Arabia, some tribes impose the same penalty for the unauthorized cutting of a tree as for the taking of a human
life. China has embarked upon an ambitious reforestation program,
and many other nations are following suit. Some forestry experts advocate substituting fast-growing trees for native varieties as a means
of keeping up with demand. 62 However, the vulnerability of forests of
genetically similar trees to diseases and pests calls the application of
such agricultural techniques to silviculture into question.
Improving the efficiency with which wood is used would also help
alleviate the firewood shortage. In India, using firewood for cooking
is typically less than 9 percent efficient. The widespread use of
downdraft wood-burning stoves made of cast iron could, S. B. Richardson estimates, cut northern China’s fuel requirements for heating
and cooking by half. 63 Other efficient wood-burning
devices can be
made by local labor with local materials.
Wood can be put to more sophisticated uses than cooking and space
heating. It can fuel boilers to produce electricity, industrial process
steam, or both. The size of many prospective tree-harvesting opera-
45
46
tions (about 800 tons per day) is well tailored to many industrial energy needs. Decentralized co-generation using wood would also fit in
well with current worldwide efforts to move major industries away
from urban areas. In particular, the creation of forest “plantations”
to produce fuel for large power plants at a cost comparable to that of
coal has been recommended .64 However, some researchers argue that
the cost of transporting bulk biomass should lead us to think in
terms of energy “farms” of a few thousand hectares or less.65
Trees are not the only energy crops worth considering. A number of
other land and water crops have their advocates among bioconversion
specialists. Land plants with potential as energy sources include
sugarcane, cassava (maniac), and sunflowers, as well as some sorghums, kenaf, and forah> grasses. Among the more intriguing plants
under consideration are Euphorbia
lathrtls and Euphorbia
tirncaIIi,
shrubs whose sap contains an emulsion of hydrocarbons in water.
While other plants also produce hydrocarbons directly, those proresemble the constituents in petroleum. Such
duced by Euphorbia
plants might, Nobel laureate Melvin Calvin estimates, produce the
equivalent of 10 to 50 barrels of oil per acre per year at a cost of $10
or less per barrel. Moreover, Euphorbia
thrives on dry, marginal
land .66
Several different crops could be cultivated simultaneously, a report
by the Stanford Research Institute suggests, and side-by-side cropping could allow year-round harvesting in many parts of the world.
Such mixed cropping would also increase ecological diversity, minimize soil depletion, and lower the vulnerability
of energy crops to
natural and human threats.67
Emnthusiastic reports by NASA National Space Technology Laboratories have focused attention on the energy potential in water hyacinths. Thought to have originated in Brazil, the fast-growing water
hyacinth now thrives in more than 50 countries; it flourishes in
the Mississippi, Ganges, Zambezi, Congo, and Mekong rivers, as
well as in remote irrigation canals and drainage ditches around the
world. The government of Sudan is experimenting with the anaerobic
digestion of thousands of tons of hyacinths mechanically harvested
from the White Nile. However, a recent Battelle Laboratory report discounts the potential commercial importance of water hyacinths in the
United States, in part because of their winter dormancy.68
Algae is another potential fuel. Some common types of this scummy,
nonvascular plant have phenomenal growth rates. However, current
harvesting techniques require large inputs of energy, the use of which
lowers the net energy output of algae farming. Although solar drying
would improve the energy balance, engineering breakthroughs are
needed before impressive net energy yields can be obtained.
One of the more fascinating proposals for raising energy crops calls
for the cultivation of giant seaweed in the ocean. As Dr. Howard
Wilcox, manager of the Ocean Farm Project of the U.S. Naval Undersea Center in San Diego, points out, “most of the earth’s solar energy
falls at sea, because the oceans cover some 71 percent of the surface
area of the globe.” The Ocean Farm Project, an effort to cultivate
giant California kelp to capture some of this energy through photosynthesis, presently covers a quarter-acre. But the experimental
operation will, Wilcox hopes, eventually be replaced by an ocean
farm 470 miles square. Such a sea field could, theoretically, produce as
much natural gas as the U.S. currently consumes.69
Biomass can be transformed into useful fuels in many ways, some of
which were developed by the Germans during the petroleum shortages of World War II. Although one-third to two-thirds of the energy
in biomass is lost in most conversion processes, the converted fuels
can be used much more efficiently than raw biomass. The principal
technologies now being explored are direct combustion, anaerobic
digestion, pyrolysis, hydrolysis, hydrogzsification,
and hydrogenation.
In the industrialized
world, organic energy is often recovered by
burning urban refuse. To produce industrial process steam or electricity or both, several combustion technologies can be employed:
waterwall incinerators, slagging incinerators, and incinerator turbines. Biomass can also be mixed with fossil fuels in conventional
48
boilers, while fluidized-bed boilers can be used to burn such diverse
substances as lumber mill wastec, straw, corn cobs, nutshells, and
municipal wastes.
Since trash piles up menacingly in much of the urban world, cities
can afford to pay a premium for energy-generating processes that
reduce the volume of such waste. Urban trash lacks the consistency
of coal, but its low sulfur content makes it an attractive energy
source environmentally.
Following the lead set by Paris and Copenhagen 50 years ago, several cities now mix garbage with other kinds
of power-plant fuel to reduce their solid waste volume, to recover
useful energy, and to lower the average sulfur content of their fuel.
A $35 million plant in Saugus, Massachusetts burns garbage from
12 towns, producing steam that is then sold to a nearby General
Electric factory that hopes to save 73,000 gallons of fuel oil per
day on its new fuel diet.
The next easiest method of energy recovery is anaerobic digestion-a
fermenting process performed by a mixture of micro-organisms in the
absence of oxygen. In anaerobic digestion, acid-forming bacteria convert wastes into fatty acids, alcohols, and aldehydes; then, methaneforming bacteria convert the acids to biogas. All biomass except wood
can be anaerobicaliy digested, and the process has been recommended
for use in breaking down agricultural residues and urban refuse.71
Anaerobic digestion takes place in a water slurry, and the process
requires neither great quantities of energy nor exotic ingredients.
Anaerobically digested, the dung from one cow will produce an average of ten cubic feet of biogas per day-about
enough to meet the
daily cooking requirements of a typical Indian villager.
Many developing and some industrial nations are returning to this old
technology, anaerobic digestion, for a new sourre of energy. Biogas
generators convert cow dung, human excrement, and inedible agricultural residues into a mixture of methane and carbon dioxide that also
contains traces of nitrogen, hydrogen, and hydrogen sulfide. Thirty
thousand small biogas plants dot the Republic of Korea; and the
People’s Republic of China claims to have about two million biogas
plants in operation70
India has pioneered efforts to tailor biogas conversion to small-scale
operations. After the OPEC price increases of 1973, annual gobar
(the Hindi word for cow dung) gas plant sales shot up first to 6,560
and then to 13,000. In 1976, sales numbered 25,000. “We’ve reached
take-off,” says H. R. Srinivasan, the program’s director. “There’s no
stopping us now.”
In addition to methane, other products can be derived from the biogasification of animal wastes and sewage. The residue of combustion
is a rich fertilizer that retains all the original nutrients of the biomass
and that also helps the soil retain water in dry periods. At Aurobindo
Ashram in Pondicherry, India, wastes from cows, pigs, goats, and
chickens will be gasified; the residue will be piped into ponds supporting algae, aquatic plants, and fish grown for use as animal fodder; and treated effluents from the ponds will be used to irrigate and
fertilize vegetable gardens. Experience with biogas plants in “integrated farming sys terns” in Papua-New Guinea suggests that the byproducts of such controlled processes can be ev:.:n more valuable
than the methane.72
In developing countries, decentralized biological energy systems like
that planned in Pondicherry could trigger positive social change. For
small, remote villages with no prospects of getting electricity from
central power plants, biogas can provide relatively inexpensive, highgrade energy and fertilizer. Ram Bux Singh, a prominent Indian developer and proponent of gobar gas plants, estimates that a small
five-cow plant will repay its investment in just four years.73 Larger
plants serving whole villages are even more econom;cally enticing.
However, where capital is scarce, the initial investment is often difficult to obtain. In India, the Khadi and Village Industries Commission
promotes gobar plant construction by granting subsidies and lowinterest loans. The Commission underwrites one-fifth of the cost of
individual plants and one-third of the cost of community plants. In
the poorer areas, the Commission pays up to 100 percent of the cost
of cooperative plants.
In efforts to hold down the cost of gobar plants and to conserve both
scarce steel and cement in developing lands, researchers are producing
49
new materials for use in digester construction. For example, a large
cylindrical bag, reinforced with nylon and equipped with a plastic inlet and outlet, can be installed in a hole in the ground and weighted
down in about one hour. The total cost can be as little as 15 percent
of that of conventional digesters. Other experimental models are now
being made out of natural rubber, mud bricks, bamboo pipes, and
various indigenous hardwoods. In general, the ideal biogas plant for
poor rural communities would be labor-intensive to build and operate
and would be constructed of local materials.
The principal problem plaguing Third World biogas plants are temperature shifts, which can slow down or halt digestion. Low temperatures are particularly
troublesome in Korea and China, where gas
production slumps in winter when energy demands are highest. Possible remedies include improving insulation, burying future facilities
to take advantage of subterranean heat, and erecting vinyl or glass
greenhouses over the digesters to trap solar energy for heating. Alternatively, some of the gas produced in the digester could be used to
heat the apparatus itself.
Alan Poole, a bioconversion specialist with the Institute for Energy
Analysis at Oak Ridge, estimates that methane produced at the rate
of 100 tons per day in a U.S. biogas plant would cost less than $4.00
per million Btu’s, which approximates the expected cost of deriving
commercial methane from coal. 74 In industrial countries, however,
the recent trend has been away from anaerobic digestion. In 1963,
this process was utilized in 70 percent of the U.S. wastewater treatment plants, but today it is being replaced-especially
in smaller cities
and towns-by
processes that use more energy than they produce.
The switch, which is now taking place at a capital cost in excess of
$4 billion annually, was prompted largely by digester failures. Although poor design and operator error can both lead to pH imbalances or temperature fluctuations, the principal cause of unreliability
appears to be the presence of inhibitory materials-especially
heavy
metals, synthetic detergents, and other industrial effluents.
These same industrial contaminants can also cause serious problems
if the digested residues are used as fertilizer in agriculture. Some of
these inhibitory substances can be separated routinely, but some will
have to be cut off at the source and fed into a different
process if excrement is to be anaerobically digested.
treatmen.t
Anaerobic digestion produces a mixture of gases, only one of which
-methane-is
of value. For many purpilses, the gas mixture can be
used without cleansing. But even relatively pure methane is easy to
obtain. Hydrogen sulfide can be removed from biogas by passing it
over iron filings. Carbon dioxide can be scrubbed out with lime water
(calcium hydroxide). Water vapor can be removed through absorption. The remaining gas, methane, has a high energy content.
Biogas plants have few detractors, but some of their proponents fear
that things are moving too fast and that large sums of money may be
invested in inferior facilities when significant improvements may
wait just around the corner. A recent report to the Economic Social
Commission for Asia and the Pacific said of the Indian biogas program that “the cost should be drastically reduced, the digester temperature controlled during the winter months through the use of solar
energy and the greenhouse effect, and the quality of the effluent improved,” b ef ore huge amounts of scarce capital are sunk in biogas
technology. To these misgivings must be added those of many in the
Third World who are afraid that the benefits of biogas plants may fall
exclusively or primarily to those who own cattle and land-accentuating the gap between property-owners and the true rural poor.75
To quell the fears of those with reservations about biogas development, most government programs stress community plants and cooperative facilities; and many countries are holding off on major
commitments of resources to the current generation of digesters. But,
whether small or large, sophisticated or crude, fully automated or
labor-intensive, privately-owned
or public, biogas plants appear destined for an increasingly important role in the years ahead.
While hundreds of thousands of successful anaerobic digesters are
already in operation, many other energy conversion technologies
are also attracting increased interest. Hydrolysis, for example, -an be
used to obtain ethanol from plants and wastes with a high cellulose
content at an apparent overall conversion efficiency of about 25 per-
5
5
cent The cellulose is hydrolyzed into sugars, using either enzymes or
chemicals; the sugar, in turn, is fermented by yeast into ethanol,
Though most research on hydrolysis has thus far been small in
scale, Australians have advanced proposals for producing prodigious
quantities of ethanol using eucalyptus wood as the base and concentrated hydrochloric acid as the hydrolyzing
agent. Ethanol so produced could substitute for a large share of Australia’s rising oil imports.76
Pyrolysis is the destructive distillation of organic matter in the absence of oxygen. At temperatures above .5OO”C, pyrolysis requires
only atmospheric pressure to produce a mixture of gases, light oil,
and a flaky char-the
proportions of each being a function of
operating conditions. In particular, this process recommends itself for
use with woody biomass that cannot be digested anaerobically.
True p!irolysis is endothermic, requiring an external heat source.
Many systems loosely termed “pyrolysis”
are actually hybrids, employing combustion at some stage to produce heat. Three of the
dozen or so systems now under development are far enough along
to warrant comment. The Garrett “Flash Pyrolysis” process involves
no combustion, but its end product (a corrosive and highly viscous
oil) has a low energy content. The Monsanto “Langard” gas-pyrolysis
process can be used to produce steam with an overall efficiency of
54 percent. The Union Carbide “Purox” system, a high-temperature
operation with a claimed efficiency of 64 percent, uses pure oxygen
in its combustion stage and produces a low-Btu gas.77
Hydrogasification,
a process in which a carbon source is treated with
hydrogen to produce a high-Btu gas, has been well studied for use
with coal. But -further research is needed on its potential use with
biomass since, for example, the high moisture content of biomass
may alter the reaction. Similarly,
fluidized-bed
techniques, which
work well with coal, may require a more uniform size, shape, density,
and chemical composition than b&mass of ten provides. Experimental
work on the application of fluidized-bed
technologies to biomass
fuels is now being conducted by the U.S. Bureau of Mines in Brucetown, Pennsylvania.
“The selection of energy systems will
be partially dictated by the type of fuel
desired: the ends will specify the means.”
Hydrogenation, the chemical reduction of organic matter with carbon
monoxide and steam to produce a heavy oil, requires pressures greater than 100 atmospheres. The U.S. Energy Research and Development Administration
is paying for a $3.7-million pilot plant at Albany, Oregon; at the Albany plant, hydrogenation will be used to tap
the energy in wood wastes, urban refuse, and agricultural residues.
The selection of energy systems will be partially dictated by the type
of fuel desired: the ends will specify the means. In a sense, the development of biological energy sources is a conservative strategy,
since the products resemble the fossil fuels that currently comprise
most of the world’s commercial energy use. Some fuels derived from
green plants could be pumped through existing natural gas pipelines,
and others could power existing automobiles. Nuclear power, in
contrast, produces only electricity, and converting to an energy system that is mostly electric would entail major cultural changes and
enormous ‘capital expenditures.
Biomass processes can be designed to produce solids (wood and charcoal), liquids (oils and alcohols), gases (methane and hydrogen), or
electricity. Charcoal, made through the destructive distillation of wood,
has been used for at least 10,000 years. It has a higher energy content
er unit of weight than does wood; its combustion temperature is
Righer, and it burns more slowly. However, four tons of wood are
required to produce one ton of charcoal, and this charcoal has the
energy content of only two tons of wood. For many purposes-including firing boilers for electrical generation-the
direct use of wood
is preferable. Charcoal, on the other hand, is better suited to some
specialized applications, such as steel-making.
Methanol and ethanol are particularly useful biomass fuels. They are
octane-rich, and they can be easily mixed with gasoline and used in
existing internal combustion engines. Both were commonly blended
with gasoline, at up to 15 to 25 percent, respectively, in Europe between 1.930 and 1958. Brazil recently embarked upon a $5OO-million
program to dilute all gasoline by 20 percent with ethanol made from
sugar cane and cassava. Meanwhile, several major U.S. corporations
53
are showing keen interest in methanol. These alcohols could also fuel
low-polluting external combustion engines.78
54
The gaseous fuels produced from biomass can be burned directly to
cook food or to provide industrial process heat. They can also be
used to power pumps or generate electricity. Moreover, high quality
gases such as methane or hydrogen can be economically mo*,:ed long
distances via pipeline. A “synthesis gas” consisting of hydrogen and
carbon monoxide was manufactured from coke in most U.S. towns at
the turn of the century; known popularly as “town gas,” it was
piped to homes for lighting and cooking. A similar “local brew”
might make sense today for areas rich in trees but poor in the type of
biomass needed for anaerobic digestion. Synthesis gas can be further
processed into methane, methanol, ammonia, or even gasoline.
The price in constant dollars for oil-based fuels declined during the
1950s and 196Os, partly because uses were found for more and more
of the by-products of the refining process. Similarly, as the residues
of biological energy processes find users, the production of fuels
from biomass will grow more economically attractive.
Many biomass schemes reflect the assumption that energy crops can
supply food as well as fuel. Even the plans to cultivate islands of
deep-sea kelp include schemes for harvesting abalone in the kelp beds.
Many energy crops, including water hyacinths, have proven palatable
to cattle and other animals, once solar dryers have reduced moisture
to appropriate levels.
More sophisticated by-product development has also been planned
by students of chemurgy, the branch of applied chemistry concerned
with the industrial use of organic raw materials. In the 1930s, George
Washington Carver produced a multitude of industrial products from
peanuts, while Percy Julian derived new chemicals from vegetable oils.
And, for the record, the plastic trim on the 1936 Ford v-8 was made
from soybeans.
Organic fuels can bear many different relationships to other products.
Sometimes the fuels themselves are the by-products of efforts to
produce food (e.g., sugar), natural fibers (e.g., paper), and lumber
or wood chemicals (e.g., turpentine). Sometimes the residues of fuelproducing processes may be turned into plastics, synthetic fibers,
detergents, lubricating oils, greases, and various chemicals.
Biological energy systems are free of the more frightening drawbacks
associated with current energy sources. They will produce no bombgrade materials nor radioactive wastes. In equilibrium, biological energy sources will contribute no more carbon dioxide to the atmosphere thr n they will remove through photosynthesis; and switching
to biomass conversion will reduce the cost of air pollution control
since
the raw materials contain less sulfur and ash than many other
r
fuels
do. Indeed, some biological energy systems would have positive
environmental impacts. Reforestation projects will control soil erosion, retard siltation of dams, and improve air quality. One type of
biomass, water hyacinths, can control certain forms of water pollution, while others remove many air pollutants.
Without wise management, however, biological energy systems could
engender major environmental menaces. The most elementary danger
associated with biomass production is robbing the soil of its essential
nutrients. If critical chemicals in the soil are not recycled, this “renewable” energy resource will produce barren wastelands.
Recycling nutrients can, alas, bring its own problems. First, if industrial wastes are included in the recycled material, toxic residues
may build up in the soil. Some evidence suggests that certain contaminants-especially
such heavy metals as cadmium and mercuryare taken up by some crops. Second, some disease-causing agents,
especially viruses, may survive sewage treatment processes. Many of
these potential infectants found in wastes can be controlled simply by
aging the sludge before returning it to the soil. But, during outbreaks of particularly virulent diseases, human excrement will have
to be treated by other means, such as pasteurization, before being applied to agricultural lands.
Because of the relatively low efficiency with which plants capture
sunlight, huge surfaces will be needed to grow large amounts of
55
56
biomass. If biological energy farms significantly
alter existing patterns of surface vegetation, the reflectivity and the water-absorption
patterns of immense tracts of land could change. Moreover, new demands for gigantic tracts of land may eventually intrude upon public
reserves, wetlands, and wilderness areas.
Ocean farming can go overboard too. The surface of the deep ocean
is largely barren of plant nutrients, and large-scale kelp farming of
the deep ocean might involve the use of wave-driven pumps to pull
cold, nutrient-rich
water from the depths up to the surface. A
100,000-acre farm might require the upwelling of as much as two billion tons of water a day, with unknown consequences for the marine
environment. Deep waters also contain more inorganic carbon than
surface waters do; upwelling such waters would entail the release of
carbon dioxide into the atmosphere. (Ironically, a classic defense of
biological energy systems has been that they would avoid the buildup of atmospheric CO2 associated with the combustion of fossil
fuels.) All these effects might be somewhat mitigated if ocean farms
were located in cooler regions to the north and south, where the
temperature difference between surface waters and deep waters is less.
If the quest for energy leads to the planting of genetically similar
crops, the resulting monocultures will suffer from the threats that
now plague high-yielding
food grains. Vulnerability
to pests could
necessitate widespread application of long-lived pesticides. An eternal
evolutionary race would begin between plant breeders and b,lights,
rots, and fungi. Moreover, biological energy systems are themselves
vulnerable to external environmental impacts. A global cooling trend,
for example, could significantly alter the growing season and the net
amount of biomass an area could produce.
Using biomass conversion requires caution and respect for the unknown. If the expanded use of biological energy sources in equatorial
countries resulted in the spread of harvestin
technologies designed
for use in temperate zones, dire effects coul Lf follow. If the biomass
fuels became items of world trade instead of instruments of energy independence, the sacking of Third World forests by multinational
lumber and paper companies could be accelerated.
“The broad social effects of biological
energy systems defy pat predictions.”
The broad social effects of biological energy systems defy pat predictions. Biological ener y systems could, for exam le, be designed to be
labor-intensive and a iihly decentraiized, but tK ere is. no guarantee
that they will evolve t 1s way of then own accord. Like all rnnovations, they must be carefully monitored; like all resources, they must
be used to promote equity and not the narrow interests of the elite.
Photosynthetic fuels can contribute significantly to the world’s commercial energy supply. Some of these solid, liquid, and gaseous fuels
are rich in energ’y; and most can be easily stored and transported.
Plant power can, without question, provide a large source of safe,
low-polluting,
relatively inexpensive energy. But all energy systems
have certain intractable limits. For photosynthetic systems, these include the availability of sunlight and the narrowness of the radiation
range within which photosynthesis can occur. Access to land, water,
and nutrients will also set production boundaries. And, at a more
profound level, we must ask how much of the total energy that
drives the biosphere can be safely diverted to the support of a single
species, Homo sapiens.
Storing Sunlight
Jets and trucks cannot run directly on sunbeams. At night, of course,
nothing can. Solar energy is too diffuse, intermittent, and seasonally
variable to harness directly to serve some human needs. Of course,
interruptions of various kinds plague all energy systems, and storage
problems are not unique to renewable power sources. Electrical
power lines snap, gas and oil pipelines crack, dams run low during
droughts, and nuclear power plants frequently need repairs and
maintenance. A wind turbine on a good site with sufficient storage
capacity to handle a IO-hour lull could, Danish physicist Bent Stirensen has shown, deliver power as reliably as a typical modern nuclear
power plant. Reliability is thus a relative concept.79
Sometimes the intermittent
nature of an energy source causes no
problems. For example, solar electric facilities with no storage capacity can be used to meet peak demands, since virtually all areas have
57
58
their peak electrical demands during daylight hours. Some users, such
as fertilizer producers, may find that an intermittent energy source
satisfies their needs. And sometimes two intermittent sources will
complement each other. For example, wind speeds are usually highest
when the sun is not shining, so wind and solar devices can often be
effectively used in tandem.
Often, however, energy must be stored. One option is to store energy
as heat. Low-temperature heat for warming buildings, for example,
can be temporarily stored in such substances as water or gravel; in
fact, substantial short-term heat storage capacity can be economically
designed into the structural mass of new buildings. For longer periods, eutectic (phase-changing) salts are a compact, effective storage
medium. Higher-temperature
heat, suitable for generating electricity,
can be stored in hot oil or perhaps in molten sodium. A 1976 report
for the U.S. Electric Power Research Institute rated thermal storage
(along with pumped hydro-stora e and compressed air storage) as
one of the most promising options Bor central utilities.80
Many solar enthusiasts are intrigued by hydrogen storage systems.
The distinguished British scientist and writer J. B. S. Haldane predicted in a lecture given at Cambridge University in 1923 that
England would eventually turn lor energy to “rows of metallic windmills working electric motors.” Haldane then went on:
At suitable distances, there will be great power stations
where during windy weather the surplus power will be
used for the electrolytic decomposition of water into
oxygen and hydrogen. These gases will be liquefied and
stored in vast vacuum jacketed reservoirs, probably sunk
in the ground . . . . In times of calm, the gases will be recombined in explosion motors working dynamos which
produce electrical energy once more, or more probably
in oxidation cells.81
Little has been done to advance large-scale hydrogen usage since
Haldane startled Cambridge with his vision more than a half century
ago. The reason for the lapse is easy enough to fathom; fossil fuels
were for decades so cheap that hydrogen could not be made competitive. In recent years, interest in hydrogen has revived, partly because
this fuel has been used so successfully in space exploration programs 59
and partly because natural gas companies have gradually begun to
awaken from their “pipe dreams” of endless natural gas supplies.
Under some grand schemes, hydrogen would someday substitute for
all natural gas, replace all automobile fuel, and satisfy much of
industry’s total energy demand as well. But the most far-fetched of
such plans for a “hydrogen economy” strain the imagination. The
easiest way to make hydrogen (other than by re-forming fossil hydrocarbons) is by electrolyzing water; the United States would have to
triple its present electrical generating capacity in order to substitute
hydrogen for the natural gas it now uses-even if it were to devote
all its electricity to the task.
Hydrogen production poses a technical problem but it is one that
may eventually yield to a cheap technical solution. In fact, some
promising research is now being conducted on biological production
processes and on techniques for using high-temperature solar heat to
split water molecules into hydrogen and oxygen. In the meantime,
hydrogen recommends itself for use in storing and transporting energy from intermittent sources of power. Easily stored as a pressurized gas, as a super-cooled liquid, or in metal hydrides, hydro en
can also be transported long distances more economically than eBectricity and can be used in fuel cells (where it can be efficiently converted into electricity in decentralized facilities). Pressurized hydrogen
tends to embrittle some metals and alloys, but the importance of this
problem has probably been exaggerated.82
Pumped hydro-storage involves using surplus power to pump water
from a lower reservoir to an elevated one. Then, when power is needed, the water is allowed to flow back to the lower pool through a turbine. Pumped hydro-storage is already used with conventional power
plants around the world; in the future it may be crossbred with windpower technologies. The use of wind energy declined in Denmark a
half century ago in part because “wind muscle” could not compete
economically with cheap, surplus Swedish hydropower,
Now that
60
demand for electricity has increased in both countries, both are seriously considering investing in a hybrid system. Danish wind power
could replace some Swedish hydropower when the wind blows, and
any surplus wind power could be used to pump downstream water
back into some of Sweden’s reservoirs. Sweden might also pursue
wind power independently. The Swedish State Power Board has decapacity could be
termined that 5,000 megawatts of wind-power
linked with current hydro-electric facilities without providing extra
storage. Such a combination of wind power and hydropower would
make sense in many places: when a dam has excess capacity and
could generate more electricity without adding more turbines if only it
held more water, a hybrid system fits the bill. The Bonneville Power
Administration
is considering the integration of wind turbines into its
extensive hydro-electric system in the northwestern United States.
Another form of mechanical storage involves pumping pressurized
air into natural reservoirs (e.g., depleted oil and gas fields), man-made
caverns (including
abandoned mines), or smaller specially-made
storage tanks. Air stored in this manner is released as needed to
drive turbines or to run machinery. For almost four decades, designers have studied large-scale pumped-air storage proposals, but the
first commercial unit is just being completed. Located in Huntorf,
West Germany, the system will store the surplus power generated by
nuclear reactors during periods of low power-demand.83
Still another approach to mechanical storage involves rapidly rotating flywheels in environments that are almost friction-free. Recent
major advances in materials now allow the construction of “superflywheels” whose higher spinning speeds enable them to store large
amounts of energy in rather small areas. Flywheels could, in theory,
be made smnil and efficient enough to propel individual automobiles.
They have already been used in pilot projects on trolleys and buses
to recapture the energy that would otherwise be lost during braking.
Although superflywheels
seem attractive at first blush, significant
problems remain; and these devices are some years away from widespread commercial application.84
Electricity can be stored directly in batteries. Existing batteries are
rather expensive, have low power and energy densities, and do not
“Overall, the storage requirements for a
society based on renewable energy
sources may prove comparable to those
of an all-nuclear society.”
last long. However, experimental batteries, some of which may prove
economical and feasible when used with intermittent energy sources,
may soon enter the market. Metal-gas batteries, like the zinc-chloride
cell, use inexpensive materials and have relatively high energy densities. Alkali-metal
batteries perform very well, but operate at high
temperatures, and existing models suffer from short life spans. A
number of other battery possibilities are being investigated and some
promising preliminary research results are now emerging.85
Base-load sources of electricity, such as coal plants and nuclear plants,
also require storage. Such facilities cannot be geared up and down to
follow the peaks and valleys of electrical usage; they produce power
at a steady rate, and surplus power from non-peak hours must be
stored for the periods of heaviest demand. For base-load plants, the
cost of storage varies with the degree to which consumer usage is not
constant 24 hours a day. For solar sources, the stora e costs vary
with the extent to which usage does not coincide wit VI the normal
daytime sunlight cycle. Wind power is less predictable, but at choice
sites tends to be quite constant. Storage problems with hydropower
and biomass systems are minimal. Overall, the storage requirements
for a society based on renewable energy sources may prove comparable to those of an all-nuclear society.
Storage ranks high among the uncertainties that impede the use of
long- term energy sources. Although studies have been performed,
none has yet established which storage systems will have an economic
edge. It is clear, however, that storage devices should be carefully
keyed to the actual q;!3lity of energy needed for a particular end-use,
and that electricity should never be produced and stored for a job
requiring only low-grade heat. In storage as in energy production itself, thermodynamics will be crucial.
Turning
Toward the Sun
We are not running out of energy. But we ure running out of cheap
oil and gas. We are running out of money to pay for doubling and
redoubling an already vast energy supply system. We are running out
61
*
62
of political willingness to accept the social costs of continued rapid
energy expansion. We are running out of the environmental capacity
needed to handle the pollutants generated in conventional energy
production. And we are running out of time to adjust to these new
reali,ties.
Humankind is no closer today than it was two decades ago to finding
a replacement for oil, and the rhetoric that public officials lavish upon the energy “crisis” is still not being translated into action. Most
energy policy continues to be framed as though it were addressing a
problem that our grandchildren will inherit. But the energy crisis is
OUT crisis. Oil and natural gas are our principal means of bridging
today with tomorrow, and we are burning our bridges.
The energy crisis demands rapid decisions, but policies must nevertheless be formulated with an eye to their wide-reaching implications.
The world will not undergo a major energy transition without also
undergoing fundamental social and political changes. The changes
some energy alternatives dictate may be preferable to others, but some
form of fundamental change is inevitable.86
If small-scale, decentralized renewable-energy
technologies were
embraced, few aspects of modern life w.ould go unaffected. Farms
would begin to rely on wind power, solar heaters, and waste conversion technologies to supply a large fraction of their energy needs.
Food storage and preparation would similarly grow dependent upon
in the
solar-powered
technologies. Gradually, meat consumption
industrial world would drop, and the food-processing industry would
become more energy-efficient and less pervasive in its impact on diets.
In the new energy era, transportation would be weaned from its
petroleum base even as improved communications
and intelligent
city planning began to eliminate pointless travel. Energy efficiency
and load factors would become important criteria in evaluating transport modes, and the costs of travel would reflect these values. Bicycles
would begin to account for an important fraction of commuter traffic,
as well as of other short trips. And freight would be transferred
wherever possible from trucks ami planes onto more efficient modes,
especially trains and ships.
If we were to opt for the best renewable-en
“7 technologies, buildings could be engineered to take full advantage “1. their environments.
More and more of the energy needed for heating and cooling would
be derived directly from the sun. Using low-cost photovoltaics that
convert sunlight directly into electricity, many buildings could eventually become energy self-sufficient. New jobs and professions would
develop around the effort to exploit sunlight, and courts would be
forced to consider the “right” of building owners not to have their
sunshine blocked by neighboring structures.
While industry would doubtless turn to coal for much of its energy
during the transition period, eventually it would also draw its primary energy from natural flows. Thus, energy availability would play
an important role in determining the locations of future factories. The
sunshine-rich nations of the Third World, where raw materials and
renewable energy sources are most plentiful, could become new centers of economic productivity.
The across-the-board substitution of
cheap fuel for human labor would be halted. Recycled metals, fibers,
and other materials would become principal sources of raw materials.
Seen as energy repositories, manufactured products would necessarily become more durable and would be designed to be easily repaired
and recycled.
Using small, decentralized, and safe technologies makes sense from
a systems-management point of view. Small units could be added
incrementally if rising demands required them, and they would be
much easier than large new facilities to integrate smoothly into an
energy system. Small, simple sources could be installed in a matter
of weeks or months; large, complex facilities often require years
and even decades to erect. If gigantic power plants were displaced by
thousands of smaller units dispersed near the points of end-use, economies of size would become relatively less important vis-a-vis economies of mass production. Technology would again concern itself
with simplicity and elegance, and vast systems with elaborate control
mechanisms would become extinct as more appropriately scaled facilities evolved.87
-I.o decentralize power sources is in a sense to act upon the principle
0 If “safety in numbers.” When large amounts of power are produced
64
at individual facilities or clusters of plants, the continued oper;ltinn
- m--m
of these plants ‘becomes cruciai to society. Where energy production
is centralized, those seeking to coerce or simply to disrupt the cornmunity can easily acquire considerable leverage: for example, a leader
of the British electrical workers recently noted that “the miners
brought the country to its knees in eight weeks,” but that his coworkers ” could do it in eight minutes.” Disruption
need not be
intentional either. Human error or natural phenomena can easily upset fragile energy networks that serve wide areas, while use of diverse
decentralized sources could practically eliminate such problems.
However, research on direct and indirect solar sources will not automatically produce devices that meet the diverse needs of the world’s
peoples. Every technology embodies the values and cenditions of the
society it was designed to serve. Most significant research on sustainable energy sources has been carried out in industrialized countries;
technological advances have therefore reflected the needs of societies
with temperate climates, high per capita incomes, abundant material
resources, sophisticated technical infrastructures,
expensive labor,
good communication
and transportation
systems, and well-trained
maintenance personnel. Such societies are wired for electricityindeed, two-thirds of the U.S. solar energy research budget is devoted
to the generation of electricity.88
Clearly, some of the findings of research conducted in such nations
are not easily or wisely transferred to societies with tropical climates,
low per capita incomes, few material resources, stunted technical
infrastructures,
cheap labor, poor communications,
and only fledgling maintenance forces. Most people in the world do not have electrical outlets or anything to plug into them. What they need are cheap
solar cookers, inexpensive irrigation pumps, simple crop dryers,
small solar furnaces to fire bricks, and other basic tools.
With the traps of technology transfer in mind, some argue that a
major solar research and development effort on the part of the industrialized world cannot speak to the true needs of the poorer
countries. This argument contains a kernel of truth in a husk of
misunderstanding.
Countries can choose to learn from each other’s
“Most people in the world do not
have electrical outlets or anything to
plug into them.”
experience; but each country must view borrowed knowledge
resources, geography,
through the ienS Of its Owl? lunique C’UitUre,
and institutions. The differences between such industrialized lands as
Japan and France merit note, but the differences between some Third
World countries may be more striking than the similarities. Surinam
(with an annual per capita income of $810) has energy problems and
potential solutions that bear little resemblance to those of Rwanda
(with an annual per capita income of about $60). And national
wealth is not the only relevant difference. The tasks for which energy
is needed vary from country to country. In some, the most pressing
need may be for energy to run the pumps thst bring water from a
deep water table to the parched surface. In lands with more abundant
water supplies, cooking fuel may be in desperately short supply. The
availability of sustainable resources may also differ. One region may
have ample hydropower potential, another strong winds, and a third
rofuse direct sunlight. Successful technology transfers require a
Eeen sensitivity to such differences.
Some disillusioned
solar researchers in both industrialized
and
agrarian countries contend that the major impediment to solar development has been neither technical (the devices work) nor economic
(many simple devices can be cheaply made). Instead, they claim, the
roblems have social and cultural roots. Many Third World leaders
Ii ave not wanted to settle for “second-rate”
renewable energy resources while the industrial world flourished on oil and nuclear power. Often, officials in charge of new technologies, such as windmills,
have been unable to find technicians who could maintain and repair
the sys terns. Occasionally, people given solar equipment have refused to use it because the rigid time requirements of solar technology
disrupted their daily routines or because the direct use of sunlight
defied their cultural traditions.
Many of these attitudinal impediments may now be vanishing as the
global South begins to develop its own research and development
capacity. The indigenous technologies born of this new capability
may prove quite compatible with Third World needs. Brazil’s large
ethanol program, India’s gobar gas plants, and the Middle East’s
growing fascination with solar electric technologies can all bode
65
66
well for the future of renewable energy resources. At the same time,
the people of the Third World, stunned by a simultaneous shortage
of firewood and petroleum, may be more willing than they were a few
years ago to adopt solar solutions.
In much of the global North as well, solar technologies are being embraced as important future options. In Japan, the Soviet Union,
France, and the United States, renewable resources are increasingly
being viewed as major components of future energy planning. Some
of the innovative research in these countries could well hold global
significance.
The attractions of sunlight, wind, running water, and green plants
as energy sources are self-evident. Had industrial civilization been
built upon such forms of energy “income” instead of on the energy
stored in fossil fuels, any proposal to convert to coal or uranium for
the world’s future energy would doubtless be viewed with incredulous
horror. The current prospect, however, is the reverse-a shift from
trouble-ridden sources to more attractive ones. Of the possible worlds
we might choose to build, a solar-powered one appears most inviting.
-
Notes
1. By far the largest fraction of current commercial solar usage is of biomass.
In many Third World countries, firewood, dung, and crop residues constitute
90 percent of all energy use. Calculations regarding the magnitude of this
usage can be found in Arjun Makhijani and Alan Poole, Energy and Agriculture in the Third World (Cambridge, Mass.: Ballinger, 1975), and D.F.
Earl, Forest Energy and Economic Development (Oxford: Clarendon Press,
1975). Hydropower ranks next, providing more than one-fifth of all electricity and about 3 percent of all end-use energy. See United Nations, World
Energy Supplies: 1950-1974 (New York: Department of Economic and Social Affairs, 1976).
2. F. de Winter
and J.W. de Winter, eds., Dexription
of the Solar Energy
R&D Programs in Many Nations (Santa Clara, California: Atlas Corporation, February 1976).
3. I am indebted to Professor Theodore Taylor of Princeton University for
suggesting this analysis. More information on the COz problem can be obtained in Stephen H. Schneider, The Genesis Strategy: Climate and Global
Survival (New York: Plenum Press, 1976); Bert Bolin, Energy and Climate,
(Stockholm: Secretariate for Future Studies, 1975); W.S. Broeker, “Climate Change: Are We on the Brink of a Pronounced Global Warming?”
Science, August 8, 1975; P.E. Damon and S.M. Kunen, “Global Cooling?”
Science, August 6, 1976. The problems associated with a plutonium economy are elaborated in Denis Hayes - Ntlcleur Power: The Fifth Horseman
(Washington, D.C.: Worldwatch Institute, 1976).
4. An overview of the major components of the U.S. fusion program can be
obtained from the Energy Research and Development Administration,
Fusion
Power by Magnetic Confinement Program Plan, Volumes I, II, III, and IV
(Washington, D.C.: July 1976). For an excellent survey of the technical
problems faced by fusion written from an optomistic viewpoint, see David
J. Rose and Michael Feirtag, “The Prospect for Fusion,” Technology Review,
December 1976. For a more skeptical appraisal, see the three-part series by
William Metz, “Fusion Power: What is the Program Buying the Country?”
Science, June 25, 1976; “Fusion Research: Detailed Reactor Studies Identify
More Problems,” Science, July 2, 1976; “Fusion Research: New Interest in
Fusion-Assisted Breeders,” Science, July 23, 1976.
67
--._
r
5. Comprehensive overviews of solar energy can be found in Farrington
Daniels, Direct Use of the Sun’s Energy (New York: Ballantine Books,
1974) and B.J. Brinkworth,
Solar Energy for Man (New York: John Wiley
and Sons, 1972). Two more recent articles in Technology
Review provide
excellent analyses of the solar potential: Walter E. Morrow, Jr., “Solar Energy: Its Time is Near,” December 1973, and John B. Goodenough, “The Op1976. The most exhaustive
tions for Using the Sun,” October-November
survey of all renewable energy technologies remains Wilson Clark, Energy
for Survival
(Garden City, New York: Anchor Press/Doubleday, 1974). A
recent survey of U.S. corporate interest in several of these technologies is
Stewart W. Herman and James S. Cannon, Energy Futures (New York: Inform, Inc., 1976).
6. Insight into the many vital but unnoticed
functions performed for humankind by the sun can be gleaned from Frank Von Hippel and Robert H. WilBulIetin of the Atomic Scientists, Novemliams, “Solar Technologies,”
ber 197.5, and Steve Baer, “Clothesline Paradox,” The Elements, November
1975. The temperature estimate for a sunless earth was provided in Vincent
E. McKelvey, “Solar Energy in Earth Processes,” Technology Review, April
1975.
and R. Talbot Page, “Energy Policy from an Environmental Perspective,” in Robert J. Kalter and William A. Vogely, eds., Energy
Supply and Government
Policy (Ithaca, N.Y.: Cornell University
Press,
1976); John S. Reuyl, et al., A Preliminary Social and Environmental Assessment of the ERDA Solar Energy Program 1975-2020, Vols. I and II (Menlo
Park, California: The Stanford Research Institute, 1976) found solar technologies to be environmentally attractive compared to the alternatives.
7. John V. Krutilla
Abundant
Energy: Paradise Lost?”
H. Landsberg, “Low-Cost
Resources
for
the
Future
Reprint
Number 112, De(Washington,
D.C.:
cember 1973).
8. Hans
9. The U.S. Federal Energy Administration
of Solar Collector Manufacturing
Activity;
Peterson, Director of Grummon
facturers of solar collectors.
10. Largely because conventional
publishes a semi-annual Survey
the 1977 estimate is by Ronald
Energy Systems, one of the largest manu-
fuels pose transportation and distribution
problems, the largest immediate market for expensive photovoltaic cells may,
strangely enough, be in the world’s poorest countries. Charles Weiss and
Simon Pak, “Developing Country Applications of Photovoltaic Cells,” presented to the ERDA National Solar Photovoltaic Program Review Meeting,
San Diego, California, January 20,1976.
11. M.L. Baughman
and D.J. Bottaro, Electric Power Transmission
tribution Systems: Costs and Their ,4Ilgcution (Austin: University
Center for Energy Studies, July 1975).
and Dis-
of
Texzs
12. An excellent exploration of the concept of thermodynamic matching is
in “Efficient Use of Energy: A Physics Perspective,” The American Physical
Society, January 1975. (Re rinted in U.S. House of Representatives, ComHearings,
mittee on Science and Tee Rnology, Part I, ERDA Authorization
February 18, 1975). Simpler explanations can be found in Barry Commoner,
The Poverty of Power (New York: Alfred A. Knopf, 1976), and Denis
Hayes, Energy: The Case for Conservation (Washington,
D.C.: Worldwatch Institute, January 1976).
B. Lovins, “Scale, Centralization, and Electrification in
Systems,” presented to a Symposium on Future Strategies of Energy
opment, Oak Ridge, Tennessee, October 20-21, 1976. The Canadian
in “Exploring
Energy-Efficient
Futures for Canada,” Conserver
Notes, May- June 1976.
13. Amory
Energy
Develdata is
Society
14. These issues are thoughtfully
explored in John S. Reuyl, et al., A Preliminary Social and Environmental Assessment of the ERDA ScrLzr Energy
Amory 8. Lovins, “Energy Strategy: The Road Not
Program 19752020;
Taken?” Foreign Affairs, October 1976; and less directly by Rufus E. Miles,
Jr., Awakening from the American Dream: The Social and Political Limits to
Growth (New York: Universe Books, 1976); Bruce Hannon, “Energy, Land,
and Equity,”
Washington,
presented to the 41st North American Wildlife Conference,
D.C., March 21-25, 1976; and William Ophuls, Ecology and
the Politics of Scarcity (San Francisco: W.H. FrEeman and Co., 1977).
15. Among their other virtues, flat plate collectors have a high net energy
yield. A conventional collector will deliver enough energy in less than one
year to pay back the energy used in its manufacture. Moreover, if collectors
are recycled, the energy requirements are reduced dramatically. See the various statements on net energy in Solar News and Views (International Solar Energy Society, American Section, Richmond, California) January a.ld
April 1976.
16. John A. Duffie
70
and William A. Beckman, “Solar Heating and Cooling,”
Scienrp, Vol. 191, No. 4223, January 16, 1976. A fine photographic survey
of several U.S. solar homes can be found in Norma Skurka and Jon Naar,
Design for u Limited Planet (New York: Ballantine Books, 1976). A more
A Brief
comprehensive survey is W.A. Shurcliff, Solar Heated Buildings:
Survey, 13th edition (San Diego: Solar Energy Digest, 1977). Active approaches to solar heating are described in W.A. Shurcliff, “Active-Type
Solar Heatiiig Systems for Houses: A Technology in Ferment,” Bulletin of
the Atomic Scientists, February 1976. Passive solar design is explained in
Ra mond W. Bliss, “Why Not Just Build the House Right in the First Place?”
B u h et’zn of the Atomic Scientists, March 1976, and by Bruce Anderson, “Low
Impact Solutions,” Solar Age, September 1976.
17. M. Telkes; “Thermal Storage in Sodium Thiosulfate Pentahydrate,”
sented to Intersociety Energy Commission Engineering Conference,
versity of Delaware, August 18, 1975.
preUni-
18. H.C. Fischer, ed., Summary of the Annual Cycle Energy System Workshop 1 (Oak Ridge, Tennessee: Oak Ridge National Laboratory, July 1976).
19. Complete information
on and specifications for this air conditioning system are available from the Yazaki Buhin Company, Ltd., 390, Umeda Kosai
City, Shizuoka Prefecture, Japan.
20. The Mitre Corporation, An Economic Analysis of So2ur Water and Space
Heating (Washington,
D.C.: Energy Research and Development Administration, November 1976); R.A. Tybout and G.O.G. Loff, “Solar House Heating,” Natural Resources Journal, Vol. 10, No. 2, April 1970.
21. This is the most persuasive argument available to those who favor utility
investments in solar technologies and conservation. A utility should in
theory be willing to make electricit -saving investments up to the hi h
marginal cost of new power plants, w h ereas the consumer will want to ma& e
only those investments that are sensible in light of average electrical bills.
Arguments against such utility involvement are generally based on the assumption that the utility will charge high prices for equipment and labor
while demanding an exorbitant rate-of-return on its investment. In parts of
the world where utilities are government-regulated,
this argument loses much
of its force.
22. Frost and Sullivan,
The U.S. Solar Power Market, Report No. 348, New
York, 1975. Frost and Sullivan estimates the total annual U.S. solar market
for 1985, including wind power and biomass, at $10 billion. In its A Nation
of Energy-Efficient
Buildings by 1990 (Washington, D.C.: 1975), the American Institute of Architects calculates that an ambitious program of conservation and solar development could save the United States the equivalent of
12.5 million barrels of oil a day in 1990. The institutional
obstacles such
rapid solar development would have to overcome are discussed in R. Schoen,
for BuiIdinys
A.S. Hirshberg, and J. Weingart, New Energy Technology
(Cambridge, Mass.: Ballinger, 1975).
23. Multiple-effect
solar stills are described in “Solar
Breakthroughs,” Solar Energy Digest, June 1976.
24. “French Solar-Powered
Irrigation
Energy Digest, February 1976.
Pump
Installed
Desalting
Process
in Mexico,”
Solar
25. D. Procter and R.F. White, “The Application
of Solar Energy in the Food
Processing Industry,”
presented to a meeting of the Australian and New
Zealand Sections of I.S.E.S., Melbourne, Australia, July 2, 1975.
26. Malcolm Fraser, Analysis
Energy to Provide Industrial
of the Economic Potential of Solar Thermal
Process Heat (Warrenton,
Virginia:
Inter-
technology Corporation,
1977). A concentrating
easily obtain a temperature of 288°C.
solar collector
can quite
27. The energy demand projections
used by the U.S. Energy Research and
Development Administration
to justify a massive nuclear power program
were carefully analyzed by Frank von Hi pel and Robert Williams, “Energy
Waste and Nuclear Power Growth,” Bul Petin of the Atomic Scientists, December 1976. The authors found that the projections demanded the use of
electricity for virtually everything. The most egregious example of electrical
“padding” was for industrial process heat. Virtually no electricity is used this
way today; yet the projections show the 2020 electrical demand for process
heat to be larger than that for all electricity used in the entire U.S. economy
in 1975. Fraser, in Analysis of the Economic PofentiuI, found that half of this
energy cou!d be provided by direct solar heating; most of the remaining half
can be more easily obtained from biomass or other fuels than from electricity.
28. Aden Baker Meinel apd Marjorie Pettit Meinel,
(Tucson, Arizona: privately published, 1970).
Power for the People,
71
29. Arguments
72
for closed-cycle OTECs can be found in U 5. House of Representatives, Subcommittee on Energy of the Committee on Scierrce and
Astronautics, Solar Sea Thermal Power, Hearings, May 23, 1974. Open-cycle
OTECs are advocated in Earl J. Beck, “Ocean Thermal Gradient Hydraulic
Power Plant,” Science, July 25, 1975, and in Clarence Zener and John Fetkovitch, “Foam Solar Sea Power Plant,” Science, July 25,1975.
30. An excellent series of papers was prepared under the auspices of the
American Society of International Law for the 1976 Workshop on Legal,
Political, and Institutional
Aspects of Ocean Thermal Energy Conversion.
Of particular interest is Carlos Stern’s skeptical paper, “An Economic Assessment of Ocean Thermal Energy Conversion.” For a more optimistic assessment of OTEC economics, see Clarence Zener, “Solar Sea Power,” Bulletin of the Atomic Scientists, January 1976.
31. R.H. Williams, “The Greenhouse Effect for Ocean Based Solar Energy
Systems,” Working Paper No. 21, Center for Environmental Studies, Princeton University, October 1975.
32. An excellent introduction
to photovoltaics can be found in Bruce Chalmers, “The Photovoltaic Generation of Electricity,”
Scientific
American,
October 1976. For a more detailed treatment see Joseph A. Merrigan, Sunlight to Electricity:
Prospects for Solar Energy Conversiorz by Photovoltuics (Cambridge, Mass.: MIT Press, 1975).
33. A recent technical survey of photovoltaic materials and techniques can
be found in the &volume Proceedings of the E.R.D.A. Solar Photovoltuic
Progrum Review Meeting,
August 3-6, 1976 (Springfield,
Virginia: National Technical Information Service, 1976).
34. See, for example, the testimony of Paul Rappaport and others in Sokur
Photovoltuic
Energy, Subcommittee on Energy of the House Committee on
Science and Astronautics, Washington, D.C., Hearings, June 6 and 11, 1974
35. A useful overview of the Japanese program is provided
“Solar Energy Research and Development
in Quest
Sources,” Technocrat,
Vol. 9, No. 3. See also Japan’s
(Tokyo: MIT1 Agency of Industrial Science and Technology,
by Akira Uehara,
for New Energy
Sunshine
1975).
Project
36. The two-year
payback period (for cells with an expected lifetime of
more than 20 years) has become conventional wisdom among the silicon
photovoltaic specialists. See, for example, Martin Wolfe, “Methods for LowCost Manufacture
of integrated Solar Arrays,”
and P.A. Iles, “Energy
Economics in Solar Cell Processing,” both in Proceedings of the Symposium
on the Material Science Aspects of Thin Film Systems for Solar Energy Conversion, May 20-24, Tuscan, Arizona (Washington, D.C.: National Science
Foundation, 1974). The calculations by Slesser and Hounam based upon a
two-year payback are in M. Slesser and I. Hounam, “Solar Energy Breeders,”
Nature, July 22, 1976. E.L. Ralph, Vice President for Research at Spectrolab,
claims that his company’s cells now have a payback period of 87 days, and
that the theoretical minimum would be on the order of 30 hours, according
to a personal communication with Dr. Peter Glaser of Arthur D. Little.
37. Photovoltaics
could, of course, also be used in highly centralized arrays
in areas of high insulation. The advantages of decentralization are more social than technical. At the extreme are proposals to obtain large amounts of
energy from photovoltaic cells on orbiting satellites, with the energy beamed
down to Earth via microwaves. The idea was first suggested by Peter Glaser,
“Power from the Sun: Its Future,” Science, November 1968, and has more
recently been popularized by Gerald K. O’Neill, “Space Colonization and
Quarterly,
Fall 1975. The conEnergy Supply to the Earth,” Co-Evolution
cept appears to have no insurmountable
technical flaws, but is of dubious
desirability. Simple, decentralized terrestrial uses of photovoltaics have far
more to recommend them.
38. The largest of these sailing vessels captured about four megawatts of
power from the wind. I am indebted to Professor Frank von Hippel of
Princeton University for several of the ideas in this section.
39. Surveys of the history of wind power can be found in Volta Torrey,
Wind Catchers (Brattleboro, Vermont: Stephen Green Press, 1976); E.W.
Golding, The Generation of Electricity by Wind Power (New York: Philosophical Library, 1955); John Reynolds, Windmills
and Watermills
(New
York: Praeger, 1970); A.T.H. Gross, Wind Power Usage in Europe (Spring-
field, Va.: National Technical Information
40. Palmer C. Putnam,
Co.,1948).
41. Don
Windmills,”
Hinrichsen
Power
From
Service, 1974).
the Wind
and Patrick Cawood,
June 10, 1976.
New Scientist,
(New York:
“Fresh
Van Nostrand
Breeze for Denmark’s
73
42. Herman
and Cannon, Energy Futures; see also Marshal F. Merriam,
“Wind Energy for Human Needs,” Technology Review, January 1977.
74
43. Frank Eldridge, Wind Machines (Washington, D.C.: U.S. Government
Printing Office, 1976). Another good survey of current wind technologies
(and storage technologies) is J.M. Savino, ed., Wind Energy Conversion
Systems: First Workshop Proceedings (Washington,
D.C.: U.S. Government Printing Office, 1973).
44. J.A. Potworowski
and B. Henry, “Harnessing
the Wind,” Conserver
Society Notes, Fall 1976. The cost estimate is from R.S. Rangi, et al.,
“Wind Power and the Vertical-Axis Wind Turbine Developed at the National Research Council,” DME/NAE
Q uurterly Bulletin, No. 1974(2).
45. J.T. Yen, “Tornado-Type
Wind Energy Systems: Basic Considerations,”
presented to the International
Symposium on Wind Energy Systems, St.
John’s College, Cambridge, England, September 7-9, 1976.
46. Cost estimates can be found in Federal Energy Administration,
Project
Independence
Final Tusk Force Report on Solar Energy (Washington,
D.C.: U.S. Government Printing Office, 1974); somewhat more optimistic
estimates are in David R. Inglis, “Wind Power Now!” Bulletin of the Atomic
Scientists, October 1975, and Bent Sfirensen, “Wind Energy,” Bulletin of the
Atomic Scientists, September 1976.
47. Edward N. Lorentz, The Nature and Theory of the Gerzerul CircuIution
of the Atmosphere (Geneva: World Meterological Organization, 1967).
48. A small fraction
of the planet’s wind produces some 150 million square
miles of ocean waves. Britain’s Department of Energy is spending a million
dollars a year on experimental efforts to tap the waves that constantly break
along Britain’s long, stormy coasts. Smaller fledgling programs are under way
elsewhere too, notably in Japan and the United States. More than 100 different mechanical and hydraulic wave power devices have been proposed.
Mechanical devices include the lopsided “ducks” designed by Stephen Salter
of Edinburgh to obtain the maximum possible rock from passing waves, and
the strings of contouring rafts, which work on the same principle, that
Christopher Cockerell (the inventor 01c the Hovercraft) has proposed. The
Japanese use an inverted box to capture wave energy hydraulically. When
waves rise, air is pushed out of holes in the top of the box; as the wave falls,
air is sucked in. These air currents are now used to power Japanese navigation buoys, and strings of such boxes may well be multiplied into power
sources of commercial value in the near future. See S.H. Salter, “Wave
Power,” Nature, June 21, 1974, and Michael Kenward, “Waves a Million,”
New Scientist, May 6, 1976.
49. Hydropower resource estimates are clouded by uncertain data and ambiguous definitions. For example, such estimates typically measure either the
maximum generating capacity that is usable 95 percent of the year or else the
capacity usable under conditions of average annual flow. Although these figures can differ by as much as 300 percent, those who make hydropower assessments often fail to state which figure they are using. This paper employs
the more conservative 95 percent figure and then reduces it sharply to reflect
new constraints being imposed by environmental and agricultural interests,
and also to reflect the futility of damming silt-laden streams that drain geologically unstable areas. The most comprehensive of the conventional hydropower resource estimates can be found in World Energ Conference, Survey
of Energy Resources (New York: privately published Yor the World Energy
Conference, 1974).
50. A fine survey of small-scale hydropower
Saunders, “Harnessing the Power of Water,”
California: Portola Institute, 1974).
51. Vaclav Smil, “Intermediate
ic Scientists, February 1977.
Technology
technologies appears in Robin
Energy Primer (Menlo Park,
in China,”
Bulletin
of the Atom-
52. Erik Eckholm, Losing Ground: Environmental
Stress and World
Prospects (New York: W.W. Norton, 1976). See also Ambio, “Special
on Water,” Vol. 6, No. 1, 1977.
Food
Issue
53. H. Lieth and R.H. Whittaker, eds., Primary Productivity
of the Biosphere
(New York: Springer-Verlag,
1975); D.E. Reichle, J.F. Franklin, and D.W.
Goodall, eds., Productiviiy
of World Ecosystems (Washington,
D.C.: National Academy of Sciences, 1975); E.E. Robertson and H.M. Lap , “Gaseous
Fuels” in Proceedings of u Conference on Capturing the Sun t Rrough Bioconversion (Washington, D.C.: Washington Center for Metropolitan
Studies, 1976).
54. Alan Poole and Robert H. Williams, “Flower Power: Prospects for Photosynthetic Energy,” Bulletin of the Atomic Scientists, May 1976; Makhijani
and Poole, Energy and Agricukure in the Third World.
55. P.D. Henderson,
India:
The Energy Sector (Washington,
D.C.:
“Energy Use in Rural India,” Science, June 4, 1976.
World
75
76
57. W.J. Jewell, H.R. Davis, et al., Bioconversion
of Agricultural
Wastes for
Pollution
Control
and Energy Conservation
(Ithaca, New York: Cornell
University, 1976).
58. Poole and Williams, “Flower
Power.”
59. R.H. Whittaker and G.M. Woodwell,
(Paris: UNESCO, 1971).
Productivity
of Forest Ecosystems
60. Earl, Forest Energy and Economic Development.
61. Erik Eckholm,
Worldwatch
The Other
Energy
Crisis: Firewood
(Washington,
D.C.:
Institute, 1975).
62. J.S. Bethel
and G.F. Schreuder,
Science, February 20, 1976.
63. S.B. Richardson,
Forestry
Johns Hopkins Press, 1966).
“Forest
in Communist
Resources: An Overview,”
China (Baltimore,
Maryland:
64. G.C. Szego and C.C. Kemp,
“The Energy Plantation,” U.S. House of
Representatives, Subcommittee on Energy of the Committee on Science and
Astronautics, Hearings, June 13, 1974.
65. J.B. Grantham and T.H. Ellis, “Potentials
gy,” Journal of Forestry, Vol. 72, No. 9, 1974.
of Wood for Producing
Ener-
66. Melvin
Calvin,. “Hydrocarbons
Via Photosynthesis,”
presented to the
110th Rubber Division Meeting of the American Chemical Society, San Francisco, October 5-8, 1976. Available from the American Chemical Society.
67. J.A. Alich and R.E. Inman, Effective
duce Clean Fuel (Menlo Park, California:
68. B.C. Wolverton,
Utilization
of Solur Energy
to Pro-
Stanford
Research Institute,
1974).
R.M. Barlow, and R.C. McDonald, x4pplication of Vusculur Aquatic PIants for PoIlution Remova!, Energy and Food Production in
u Biolo,qical System (Bay St. Louis, Mississippi: NASA, 1975); B.C. Wolverton, R.C. McDonald, and J. Gordon, Bioconversion
of Water Hyacinths
into Methane Guq: Part I (Bay St. Louis, Mississippi:
NASA, 1.975). The
report voicing skepticism about the U.S. potential is A.C. Robinson, J.H.
Gorman, et al., An Anulysis of Market Potential of Water Hyucirzth-Bused
Systems for Municipal
Wastewater
Treatment
(Columbus, Ohio: Battelle
Labora tories, 1976).
the Sun Through Biocon69. H.A. Wilcox, “Ocean Farming” in Capturing
version. For a less sanguine appraisal of the large ocean-farm concept, see
John Ryther’s remarks in the same volume.
77
“Reclamation of Energy from Organic Refuse: Anaerobic
Digestion Processes,” presented to the Third National Congress on Waste
Management and Resource Recovery, San Francisco, 1974; Alan Poole, “The
Potential for Energy Recovery From Organic Wastes,” in R.H. Williams, ed.,
The Energy Conservation
Papers (Cambridge, Mass.: Ballinger, 1975). A
good annotated bibliography of do-it-yourself
books on biogas plants apTechnology
Sourcebook
pears in Ken Darrow and Rick Pam, Appropriate
(Stanford, California: Volunteers in Asia Press, 1976.)
70. J.T. Pfeffer,
71. Smil, “Intermediate
!ZZ. Report
Technology
in China.”
of the Preparatory
fion (Manila:
Mission on Bio-gas TechnoIogy and UtilizuEconomic and Social Commission for Asia and the Pacific,
1975).
73. Ram Bux Singh, Bio-Gus Plant (Ajitmal,
Station Publication, 1971).
Etawah, India: Gobar Research
74. Poole and Williams, “Flower Power.”
75. C.R.
Prasad, K.K. Prasad, and A.K.N. Reddy, “Bio as Plants: Prospects, Problems, and Tasks,” Economic and Political Wee a ly, Vol. IX, No.
32-34,1974.
76. R.N. Morse and J.R. Siemon, Solar Energy for Australia:
The Role of
Biologica 81 Conversion,
presented to the Institution of Engineers, Australia,
1975.
77. G.C. Floueke and P.H. McGauhey, “Waste Materials,” in J.M. Hollander, ed., Annual Review of Energy, Vol. 1 (Palo Alto, California: Annual
Reviews, Inc., 1976).
78. For a ood overview of the Brazilian ethanol program, see Allen L. Hammond, “A f cohol: A Brazilian Answer to the Energy Crisis,” Science, February 11, 1977. American interest in methanol is surveyed in Edward Faltermayer, “The Clean Synthetic Fuel That’s Already Here,” Fortulle, Septem-
ber 1975.
79. Bent S$rensen, “De endability of Wind Energy
Term Energy Storage,” spciencp. November 26, 1976.
78
Generators with Short-
80. Public Service Electric and Gas Company of New Jersey, An Assessment
of Energy Storage Systems for Use by Electric Utilities (Palto Alto, California: Electric Power Research Institute, 1976).
81. Clark, Energy for Survival.
82. A comprehensive recent article by some of the foremost proponents of a
“hydrogen economy” is D.P. Gregory and J.B. Parghorn, “Hydrogen Energy I” in Jack M. Hollander, ed., Annual Review of Energy; a somewhat more
skeptical appraisal is in J.K. Dawson, “Prospects for Hydrogen as an Energy
Source,” Nature, June 21, 1974. The fuel cell is a device that produces electricity directly from fuel through electrochemical reactions. Invented in 1839
by Sir William Grove, the fuel cell has been put to practical use in the space
program. The United Technologies Corporation has embarked upon a $42million research effort to develop a commercial fuel cell, and U.S. utilities
have already signed options for the first 56 units produced. Vigorous research is also under way in many other countries.
Fuel cells have several major advantages over conventional technologies.
They involve no combustion and hence virtually no pollutants. Sixty-percent
conversion efficiencies are common, and 75-percent efficiencies have been
reported. Unlike conventional power plants, fuel cells are as efficient with a
partial load as with a peak load. Moreover, their modular design shortens
construction lead times, since new modules can be added as needed. The use
of decentralized fuel cells would also save the expense of constructing power
lines from huge generating facilities, and would allow waste heat to be productively employed. Fuel cells are quiet, and they conserve water.
See R.S. Tantram, “Fuel Cells Past, Present, and Future,”
Vol. 2, No. 1, March 1974.
Eneryy
Policy,
83. H.C. Herbst, “Air Storage-Gas Turbine: A New Possibility of Peak Current Production,” Proceedings of the Technical Conference on Storage Systems for Secondary Energy, Stuttgart, Federal Republic of Germany, October
1974. For a broad overview of this technology, see also A.J. Giramonti and
R.D. Lessard, “Exploratory
Evaluation of Compressed Air Storage PeakPower Systems,” Energy SozArces, Vol. 1, No. 3, 1974; and D.L. Ayers and
D.R. Hoover, “Gas Turbine Systems Using Underground Compressed Air
Storage,” presented to the American Power Conference, Chicago, April 29May 1,1974.
84. Fritz R. Kalhammer and Thomas R. Schneider, “Energy Storage,” in
Jack M. Hollander, ed., Annual Review of Energy. See also Julian McCaull,
June 1976. Much interesting material con“Storing the Sun,” Envirorlmerlt,
cerning flywheels and other storage devices can be found in J.M. Savino,
ed., Wind Energy Conversion Systems, First Workshop Proceedings (Washington, D.C.: National Science Foundation, December 1973).
85. A good survey of current battery prospects is in Kalhammer and
Schneider, “Energy Storage.” An interesting new battery idea is described in
M.S. Whittingham, “Electrical Energy Storage and Intercalation Chemistry,”
Science, June 11, 1976.
86. For example, some argue that storing energy from rcnewable sources
would require people to change their lifestyles to conform to the periodicity
of such sources. However, similar lifestyle adjustments will attend the switch
to nuclear as well as solar substitutes for oil and gas. Storage costs will motivate users of solar energy sources to schedule their energy-using activities for
daylight hours. Similarly, the cost of storing nuclear power will encourage
consumers to even out their daily energy use. In neither case is the requirement absolute, but in both people will be rewarded for tailoring demands to
fit su plies. The social changes a successful solar transition entails are discu sseY more fully in Denis Hayes, Rays of Hope: The Transition to R PostPetroleum World (New York: W.W. Norton, 1977).
87. E.F. Schumacher,
Small is Beautiful:
(New York: Harper and Row, 1973).
88. The proportion
Economics as if People MattereA
of U.S. funding being applied to solar electrical generation will decline in fiscal year 1979. It is to be hoped that any cuts will be
aimed at the centralized options rather than at photovoltaic research. There
are not many research goals as attractive as an inexpensive, efficient photovol taic cell.
DENIS HAYES is a Senior Researcher with Worldwatch Institute and
author of Rays of Hope: The Transition
to II Post-Petroleum
World
(W. W. Norton, 1977). His research encompasses alternative global
energy strategies, energy conservation, and nuclear proliferation. Prior to joining Worldwatch, he was director of the Illinois State Ener y
Office, a guest scholar at the Woodrow Wilson Center of the Smit a sonian, and head of Environmental Action.
” THE WORLDWATCH
PAPER SERIES
I.. The Other Energy Crisis: Firewood
by Erik Eckholm.
2. The Politics and .Responsibility
basket by Laster R. Brotin.
3. Womerz in Politics:
4. Energy:
of
A Global Review
The Case fpr Conservation
the North
American
by Kathleen Newland.
by Denis Hayes.
5. Twenty-two,Dimensions of then Population
Problem
Brown, Patricia L. McGrath, and Bruce Stokes.
6. Ndear
Power:
The Fifth Horseman
7. The Unfinished
Assignment:
by Patricia L. McCrath.2
8. World Population
Lester R. Brown.
9. The TWO
Record.
Trends:
Faces of Malnutririon
by Lester R.
by Denis Hayes.
Equal
Signs
Bread-
of
Edtlcation
Hope,
by Erik
Signs
Eckholm
for
of
Women
Stress
by
and Frank
10. ife~lth: The Fanzily PIm797i97g Factor by Erik Eckholm and Kathleen Newland.
11.. Ener*gy:
The Solar Prospect
by Denis Hayes.
Worldwatch
publications are available on a subscription basis for
$zs.OO a year. Subscribers receive all Worldwatch papers and books
published during the calendar year for a single annual subscription.
Single co ies of Worldwatch Papers, including back copies, can be
purchase cr for $2.00. Bulk copies are available at the following prices:
2-10 copies, $1.50 per copy; 11-50 copies, $1.25 per copy; and 51
or more copies, $1.00 per copy.
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Institute
e77e 1“4 .issachuset ts Avenue, N. W.
?%d:im$on,
D.C. 20036 USA
’
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