Electric Vehicle Charging. How, When and Where? - E-P2SE
Electric Vehicle Charging. How, When and Where?
1.- INTRODUCTION
The Electric Vehicle (EV) is a media reality that
does not represent the scarce number of vehicles
circulating through our roads.
This situation will change when car dealer's
showrooms (cars, motorcycles, bicycles, industrial
vehicles, buses, etc.) start to exhibit these vehicles.
Such a change will be effective within a few months
and, in particular, during the next few years, since
the major car manufacturers are developing their
own EVs.
This article wishes to illustrate the EV charging infrastructure scenario, as well
as the most suitable places, moments and methods to charge them.
2.- WHY IS IT NOW POSSIBLE?
The EV is not something new. The first
electric car was built by the British
inventor Thomas Parker in the year
1884.
Ford's first "T" models appeared by the
dawn of the XX century, which was
produced in series and with acceptable
costs, with an internal petrol combustion
engine that revolutionized the automobile
industry. Such an impact has lasted until
now. Various causes have made it
possible to change the trends in favor of
a progressive increase of the EV in our everyday reality.
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October, 2010
The need to protect the environment, which is increasingly being harmed by the
CO2 emissions (greenhouse effect), contaminating effects, such as CO
(poisonous gas), in addition to the noise in large cities is also a powerful
reason.
Therefore, the new generations must address such issues, increasing the
awareness of developed countries (with the new global order, they pay more
taxes for higher rates of contamination).
Spain, as other European countries, are highly dependent on energy from
abroad. We import crude oil, gas, enriched uranium and carbon.
We generate a high amount of electrical energy with natural resources (wind,
sun, water,..).
The paradox lies in the fact that the latter are often disconnected from the grid
when the demand for electricity is not high enough (nuclear power or combined
cycle plants need more hours or even days to stop and start-up their production
systems).
Therefore, our country should reduce its current energy dependence, all the
more since more than 75% of the crude oil imported is consumed by the
transport sector.
Another factor that has had a big impact in the implementation of the EV is the
technological advances in the electrical battery sector.
The modern Ion-Lithium batteries increase the energy capacity of traditional
Lead batteries by five. Progress is being made in other high-performance
electricity storage technologies, such as, for example, super-capacitors.
To this end, the governments of surrounding countries have taken these matters
into their own hands and are already creating aid plans and regulations in favor
of the EV.
The most popular one in Spain is the "Movele Plan" proposed by the Ministry of
Industry through its organization for energy savings, the “IDAE”.
Furthermore, the “Cenelec” standard committee is launching a new standard for
the EV charging, the IEC 61851, which will settle the necessary statements for a
common method of EV charging in Europe, an surely will influence other word
areas.
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October, 2010
3.- TYPES OF ELECTRIC VEHICLES
Evidently, electrical motor drive can be applied to any type of vehicle, from a
bicycle to a bus.
The most complex part lies in the use of an "electricity storage system" in the
form of a battery that can offer a certain battery range.
Broadly speaking, there are four types of electric vehicles:
a.- Hybrid vehicles that can NOT be connected to the grid
b.- Hybrid vehicles that can be connected to the grid
c.- Hybrid vehicles that can be connected to the grid, with full electrical
drive
d.- 100 % electric vehicles
Type a is not a true EV, since the electrical motor is simply used as a
support to the internal combustion. It has a battery life of 5 to 10 km with
the use of the electrical drive system.
Type b also has two drive motors: an electrical and an internal
combustion motor/engine. However, it is rechargeable and its batteries
offer a high battery range (50 to 80 Km).
Type c uses an electric motor for the drive systems and a small petrol
engine used to charge the batteries. It has a battery life of 100 to 200 Km
with the battery and up to 1000 Km when the batteries are charged with
the petrol engine.
4.- EV CHARGING METHODS
The storage capacity of a battery used in
an EV ranges from 15 to 30 KWh.
This would be the same as the energy
used to power a 100 W light bulb between
150 and 300 hours.
The battery of an EV can be charged
within minutes or in a few hours, since the
30 KWh charging process can be quick or
slow.
A quick charging process (15 min.) for a
battery that is completely flat would need
a power of 60 KW to 120 KW. A slow
charging process for the same battery (6
h) would need a power of 2.5 to 5 KW.
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The most common standarised sockets in Europe can accept a maximum power
of 3.7 KW (230V@16A), 7.4 KW (230V@32A) in single-phase networks
(domestic) and 43.6 KW (400V@63A) in three-phase networks.
The EV battery charging process requires approximately 40 KW (three -phase
system) in the quick charging mode and 3 KW in the slow charging mode
(single-phase system).
All in all, the standard (or slow) charging process would require an average of 3
KW, which can take place at home or with a standard garage socket, which
would charge the battery in 4 to 8 hours.
The quick charging process would require an average of 40 KW and should be
carried out in tertiary or industrial environments, which would charge the battery
in 21 to 42 minutes.
There are other experimental systems, such as the induction charging or 500
Vdc charging processes, although they need to be tested.
5.- IMPACT OF THE EV ON THE GRID
Unfortunately, the grid has a limited EV charging capacity.
The demand for electrical energy will vary during cycles that are similar to the
24 hour cycle. The demand will be higher during peak hours and lower during
the off-peak (night time) hours.
Therefore, the electrical energy generation and transport infrast ructures must
be adapted to the peak demand, but these are quite idle during low demand
periods.
Another factor that must be taken into account (especially in our country) is the
fact that the capacity to generate wind and sun energy is usually underused d ue
to the lack of demand during off-peak hours.
Therefore, the EV charging process must take place during off -peak hours when
the demand is low and the power is being generated with renewable energies.
A series of studies have concluded that the Spanish electricity system could
charge a maximum of 2.7 million EVs (10% of the current vehicles in circulation)
under determined conditions, using intelligent systems in the current system
and equipment to avoid a collapse of the grid (local or global.
Another aspect must be taken into account. This is the "grid quality". In fact, the
EV charging processes generate alterations in the grid. The most common
effects are known as "harmonics" and they can cause major problems.
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October, 2010
6.- HOW, WHEN AND WHERE?
We have already explained that the EV charging process is not a trivial matter.
The grid can accept an increase in the demand, provided that it is under a
series of conditions.
The vehicles should be charged slowly (in hours, not in minutes) and during of fpeak hours (to balance the daily demand curve). However, what is the most
suitable place to charge a vehicle?
The charging conditions will be analysed in different locations below.
In our country, a standard home (for example, a single-family home with its own
garage), has a contracted power of 4.4KW (20A) to 8.8KW (40A). Obviously, if
the charging process of an EV requires 3 KW, determined precautions must be
taken to prevent "fuses from blowing".
The first precaution would be to charge the EV at night, when most loads are
disconnected. This offers a second advantage, which is the possibility to charge
the vehicle during night-time rates, which are cheaper than day-time rates.
The situation is different in the case of community garages.
Let us assume we have a community garage with a capacity for 40 parking
spaces.
The contracted power would be approximately 10KW, out of which 4 KW would
be used by the lighting systems and the remaining KW would be used by the
mandatory air extraction and reserve systems. A single vehicle would require 3
KW for a safe charging process, as explained above.
In the third example, we will describe the scenario for an underground car park
located in the centre of the city. Let us assume that we have a capacity for 500
parking spaces.
The contracted power available would be approximately 100 KW, out of which
15 KW would be used by the lighting systems and the remaining KW would be
used by the ventilation, collection and reserve systems. 5 vehicles can be
charged, provided that a series of precautions are taken (for example, not
extracting air at night, …)
Therefore, all examples show how an EV can be charged, but specific areas
must be taken into account.
Usually, the power capacity must be expanded to charge a greate r number of
VEs.
Clearly, the charging process must use intelligent systems (not a simple
socket).
This is the only method to charge EVs under safe conditions in a local
installation and with the use of the grid.
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October, 2010
7.- CONCLUSIONS
The electric vehicle is a reality.
Our society needs it. All major car manufacturers will be exhibiting them in their
car dealers' showrooms within a few months.
Therefore, we must create the charging infrastructures in the most adequate
places.
The vehicle can be charged with different methods and in different
environments and there is a standard in process of launching for it (IEC 61851 1).
We must highlight the suitability of parking spaces and garages (in the centre of
the city, in shopping malls, at work) to charge EVs when compared to other
potential places (we do not forget the main place, the domestic charge at
home).
The charging process will take a few hours and
at a low power rating (not in a few minutes at
high power ratings), to make the most out of
the existing capacity of the grid in off-peak
hours. In addition, the parking spaces or
garages offer the possibility of complementary
charging process that take 2 hours and a half
during the rest of the day, increasing the
performance and efficiency of each charging
point.
The parking space or garage offer the
possibility of intelligent charging processes, adapting the charge to the
availability of the grid, in order to protect it against harmful alterations (harmonic
currents) produced by the charging process, while offering information about the
availability of parking spaces to the user and incidents and a histogram to the
owner - operator in real time. Power expansions will be required in the electrical
connections in the medium-term to charge a higher number of EVs.
Therefore, it is clear that the charging process of an EV does not rely on a
simple socket, but on an intelligent and safe system that can communicate with
other systems.
Joan Hinojo
Managing Director of CIRCONTROL / ASESGA’s technical advisor
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