Shiyala Village Solar Classroom Project – August 2012

Shiyala Village Solar Classroom Project
– August 2012
Version
0.0
1.0
Date
07/09/2012
11/09/2012
By
LT, DR
LT, DR
Description
First Draft
Amendment following JEH comments/suggestions.
Earthing arrangement decisions described.
1
Introduction
Two School of Engineering staff members designed and installed a solar classroom at a remote
medical outpost in Zambia. The School of Engineering lent support to the project by funding the
travel costs of Dr Daniel Rogers and Mr Lee Thomas. The work was undertaken with the charity
‘Mothers of Africa’, led by Professor Judith Hall, whose principal aim is to contribute to the delivery
of the Millennium Development Goals by improving medical practice in African countries through
education.
The team successfully installed a 1200W solar array with four 220Ah (total capacity 10.56 kWh)
AGM batteries. The new system supplies nine computer bays within the classroom, general 230V
lighting/power, a vaccination fridge and a neighbouring building.
It is envisaged that the new facility will be used as an adult education facility for the surrounding
district. The use of the new facility will be determined by the local community, who contributed
labour and time to the project. Whilst the primary aim of the facility is to disseminate best practice in
the basics of medicine, the existence of an accessible IT provides a means to improve computer
literacy. The facility also enables the possibility of homework/learning club to take place after dark.
2
Overview of Installation
2.1
Preparation
The preparation phase began with briefing sessions attended by Prof. Hall, Dr Rogers and Mr
Thomas. In these meetings the team agreed rough building dimensions and project aims. It was agreed
that ABESU, a charity specialising in construction and focussing their efforts on the village of Shiyla
in Zambia, would arrange for the construction of the building and that Aleutia would be used as the
main supplier of the computers and solar panels.
As part of the preparation process draft layouts, schematics and equipment schedules were drawn up.
The initial equipment schedule can be found in Appendix I. Appendix IV includes the final schematic
drawing. The computers and solar panels were purchased from Aleutia and the remaining items were
purchased from RS, Edmundson Electrical and Screwfix. The equipment and tools were shipped, via
Aleutia, to Zambia around a month before the team’s departure. Owing to their weight, batteries were
sourced in Lusaka. After clearing customs the equipment was stored in a secure shipping container
near Chongwe.
2.2
In Zambia
The Zambian national health board provided the team with a Toyota Land Cruiser and a driver,
Jonathan. The first task, following a brief post-flight nap, was to check that the pre-shipped equipment
had survived the journey. Once this was done the new classroom building was visited.
The team arrived to find that concreting of the floor was underway in one room. Whilst there had been
some departure from the original plans (e.g. the switchroom and office were swapped) the building
was broadly as expected. Introductions were made to the group of around nine men that were working
on the building.
Figure 1 - The group of men working on the project on arrival (and Dr Rogers)
The next task was to purchase batteries from a Zambian supplier. A Lusaka based company, ‘Suntech’, was used. The batteries (each weighing around 65 kg) were purchased and taken to site using
the Land Cruiser. After picking up the equipment and tools from the lock-up the project was ready to
progress.
At the beginning of the week the main equipment items were mounted on the wall of the switchroom.
These items included; a rotary isolator, a maximum power point tracker, the 48V-DC distribution
board, the 48V-DC to 12V-DC converter, the 12V-DC distribution board, the 48V-DC to 230V-AC
inverter and the 230V-AC distribution board. The items were interconnected, in accordance with the
schematic, using armoured cabling.
The mounting of the solar panels took around a day and a half. The solar panels selected were four
Xunlight XR36 panels. These use amorphous silicon technology and are comparatively flexible. Each
of the panels comes with ten fixing grommets attached to flaps along the length of the panel. The
panels were secured using eye-bolts (bolted to the corrugated tin roof) and rope. In hindsight, the
speed of installation could have been improved by using standard bolts and washers linked directly
through the fixing grommets. However, the use of eyebolts did allow for perforation of the corrugated
roof at peaks, minimising the chance of water ingress.
The construction of the roof was such that the supply cabling from the solar panels could be threaded
through. A small gap was available where the dips in the corrugated roof met the flat panelling at the
apex. A junction box was mounted at high level (under the apex of the roof). This contained
termination blocks to allow the connection of the solar panels to the Maximum Power Point Tracker
(MPPT) in the switchroom.
Figure 2 - The installed solar panels
Figure 3 - Switchroom equipment. Wall mounted equipment from left to right; 230V-AC distribution board (wylex),
3kVA Inverter, 12V-DC distribution board, 48V-DC:12V-DC converter, 48V-DC distribution board (schneider),
Maximum power point tracker (Morningstar), solar panel isolator.
An important aspect of the project was the power supply link to the adjacent admin block. To achieve
this, a trench was dug and an armoured (3 core 6mm2) cable laid. Within the admin block a
distribution board was provided to allow the future wiring of small power and lighting. At each end of
the trench, adjacent to the buildings an earth rod was installed. These were linked using the third core
and armour of the cabling.
All extraneous metallic parts were bonded and linked to the building’s earth rod. In the new classroom
building this involved bonding the roof and the casing of each distribution panel. In the admin block
the roof was linked to the earth rod. It was advised that, in the event of a lightning storm, the
equipment should be isolated in order to protect it from damage from lightning current surges. The
decisions made in relation to the earthing arrangement are summarised below:
•
•
•
•
•
•
•
•
•
Earth rods were installed at for both buildings (Education Facility and Admin Block). These
were bonded to earth bars in the respective 240V distribution panels.
The metal roofs of both building bonded to earth bars in the respective 240V distribution
panels.
The earths for both buildings connected together over grey core of the armoured cable.
The earth bars in 48V and 12V panels were directly connected to earth bar in 240V panel in
battery room.
All power electronics kit earths were bonded to respective distribution panel earth bars using
grey core of armoured cable.
The 230V neutral was bonded to earth in battery room and admin building (AFTER RCD!)
The 12VDC negative was bonded to earth.
The 48VDC negative was NOT bonded to earth.
The Solar Panel negative was NOT bonded to earth
Unfortunately a supplier error was made when the inverter was shipped. The shipped inverter had a
rated input voltage of 12V-DC as opposed to the required 48V-DC. Regrettably, this error was only
picked up after connection; therefore some damage was caused to the inverter. An alternative inverter
was sourced, from Sun-tech, and connected into the system. Happily, the original supplier offered to
reimburse the project.
Within the classroom, a 12V-DC system was selected for supply of the computers for three reasons:
-
Avoidance of the excessive use of 230V socket outlets (which could overload the system
if too much load is connected).
Avoidance of the use of multiple 230V-AC to 12V-DC converters – thus avoiding an
additional conversion stage and improving overall efficiency.
A separate system means that the computers would be less affected by nuisance tripping
of other circuits or by the inverter capacity.
Nine 12V-DC power supply boxes were created to supply each of the computers. Standard DC
connectors were used to provide power supplies for the monitors and PCs. Additionally, a flexible 3W
LED task light was also connected to each of the boxes. As the 3W lights required a 4V power supply,
a small DC-DC converter was included in each of the boxes.
Figure 4 - 12V DC Distribution Box
The Morningstar MPPT was supplied with a remote monitoring kit. The kit monitors the battery and
solar panel voltages and the system temperature. It is able to ascertain the system state (i.e. daytime
generating or night time standby). It also reports the daily kWh supplied from the solar equipment.
The remote monitoring interface was mounted within the solar classroom.
The completed was tested. The system consists of:
-
1200W amorphous silicon solar panels with Maximum Power Point Tracker
Four 220Ah AGM batteries
A 12V-DC circuit feeding 9 task lights and two computers (with room for connection of
a further 7)
A 230V lighting circuit for the classroom and office.
A 230 V power circuit for twin socket outlets in the classroom, office and other teaching
space.
A 230V link to the admin block
Capacity of future links to the medical output building.
Figure 5 - Installed Computers
2.3
Operation and Maintenance
Instructions for the operation and maintenance of the equipment were given. This included the
procedure for energisation and de-energisation of the system. The advised turn on procedure is shown
below:
A:
48V Distribution Board
1. Batteries On
2. Solar On
B:
Panel rotary isolator On
3. 12V Supply On
4. Inverter On
C:
12V Distribution Board
5. DB isolator On
6. Short Bench On
7. Long Bench On
D:
230V AC Inverter On
8.
9.
10.
11.
Main Switch On
RCD On
All Lights On
Office Lights On
12. Classroom Sockets On
13. Admin Block OFF
The batteries chosen were 12V 220Ah Victron AGM (Absorbant Glass Matt). The lifetime of these
batteries is linked to the total number and depth of discharge and re-charge cycles they undergo. For
example, the batteries would last for only 200 cycles if discharged and recharged completely but
would last for 900 cycles if they are discharged to a minimum of 70% of capacity. Therefore, to
conserve battery life, care must be taken to not fully discharge the batteries.
The environment in Shiyala was very dusty in August. During the visit there were some wind gusts,
typically lasting no longer than 5 minutes. It was noticed that a fine layer of dust had built up on the
panels. It is recommended that panel are periodically wiped over to remove dust as a continued dust
build up could adversely affect the panel efficiency. The cleaning could be done with a mop – care
should be taken not to stand on, or otherwise apply excessive force to, the panels.
The installed remote monitoring system records the daily output of the solar panels for 200 days. This
data would be valuable to assess the utilisation and effectiveness of the system. It is recommended
that the data is collected during the next visit and that a local person is trained to monitor the data –
perhaps logging it on one of the computers.
3
Lessons Learned
The cabling links between each of the distribution boards were specified as XLPE-SWA-PVC (Cross
Linked Poly-Ethalene, Steel Wire Armoured, Poly Vinyl Chloride). Whilst use of this cabling is
common industry practice in the UK the armour makes the cable difficult to manipulate, adding to
installation time. A possible alternative for consideration in future projects could be the more flexible,
triple insulated rubber, H07-RNF cabling.
During installation there was some discussion on whether we could have use smaller cabling sizes. In
some cases, for instance the 12V DC circuit, where 10mm2 cabling was used, the cable size could
have been reduced. This would have increased the voltage drop (and therefore the energy losses) but
this could have been kept within acceptable limits by increasing the sending end voltage at the
converter (or inverter) if necessary. In order to be certain of minimum cable size specifications cable
lengths (and therefore final building dimensions) must be known in advance.
The damage caused on connection of the inverter could have been prevented by more rigorous
checking. Whilst the fundamental error was the supplier’s and the nameplate label was relatively
small, some responsibility for the damage caused to the inverter must lie with the project team. A
checking procedure may have help pick up this issue earlier and the use of a pre-prepared checklist
may also have helped.
The use of local suppliers (as opposed to using UK based suppliers and shipping out) has some
advantages. Firstly, the administration burden of shipping/customs checking is reduced. The direct
injection of money into the local economy may also have benefits. Furthermore, having a local partner
may help in resolving any last minute requirements. Finally, if the supplier has relatively large stocks,
then less extra allowances need be made in the specification of cabling. However, if the charity were
to repeat the solar classroom installation in other countries, building a relationship with UK based
suppliers may be preferable.
One challenge that was faced was how to involve the
local workforce as much as possible in the electrical
installation whilst making sure that work of sufficient
quality was achieved. The workforce was very
proficient at building tasks. For instance, a plinth for
the batteries was built within a two hours of request.
However, they were less familiar with electrical
installation techniques. The more that locals can be
involved, the better the understanding gained and the
higher the sense of ownership afterwards.
A way of involving the local workforce more would
be to create detailed drawings showing all cable
terminations and fixing techniques. These could be
followed by the local workforce and some basic work
could start in advance of the arrival of specialists.
On reflection, it is felt that the timescales allowed for
the preparation of the design were a little short.
Additionally, more time on site would have been
useful. Allowing more preparation time would have
Figure 6 - The ladder used on site. An Aluminium allowed the team to circulate proposals and to
(or similar) ladder may have increased the speed
iteratively revise them as required.
of installation
Some of the equipment used on site could have been
improved. For example, the ladder provided was quite unwieldy and took some getting used to in
practice. Also, it was found that some tools were needed at the same time in different places (e.g. wire
strippers, pliers, cutters, screwdrivers). In most cases only one tool of each type was taken to Zambia.
This sharing of tools occasionally disrupted the flow of work. Finally, the team were highly reliant on
a few relatively inexpensive items such as the 5mm drill bit; if this was to have broken it could have
disrupted the project. Therefore taking duplicate tool sets would have improved the build rate and
reduce risk of disruption due to tool failure – though this would come at the cost of extra shipping. If
similar projects are to be undertaken in future, it may be worth creating a permanent tool set in
Zambia.
During the installation it was realised that the Admin block could not be completely isolated without
isolating all of the 230V circuits. Whilst the live conductor can be disconnected using the single pole
Miniature Circuit Breaker (MCB) the neutral conductor will remain connected. This could be
relatively easily improved by changing the single pole MCB for a double pole version. Additionally, it
is recommended that a separate Residual Current Device (RCD) is installed in the admin block
distribution board. This would mean that the Admin building link need not be protected by the RCD
in the Education Facility and, if the RCD was by passed (for the Admin Block link only), the risk of
nuisance tripping of all 230V circuits would be reduced.
The selected solar panels were flexible, lightweight and relatively easy to install. However, these
advantages come at the cost of a reduced efficiency (per m2) – this was offset by allowing for a larger
surface area coverage. Monitoring of the installation should be undertaken to allow performance
comparison with traditional poly-crystalline silicon panels.
Another improvement would have been clear communication of the desired building orientation at the
outset. The roof on which the solar panels were installed was facing north west. The optimum
orientation would have been north (Zambia is south of the equator). However, it is not thought that it
will mean a large drop in energy inputted to the system. This is because the solar panel suppliers state
that the panels work relatively well in ambient (indirect) and also because the direct sunlight not being
collected occurs early in the morning (when the incident irradiation levels would be lower in any
case).
An aspect of the project that was more time consuming than envisaged was the creation of the 12VDC distribution boxes. The process involved the dismantling of pre-bought Ikea lamps, soldering of
the DC-DC converters and resistors for connection of the lamp and fixing of the switch and lamp to
the box. If this had been done before travel to Zambia then some time on-site could have been saved.
However, in this project, it would have taken away from precious preparation time in the UK.
Some non-critical bugs were found during the setting up of the computers. These included a slight
mismatch in the resolution of the screens and the available graphics output of the computers. Also, a
problem where the mouse pointer disappears on hovering over menu items was found. These
problems were communicated to the supplier. Finally, it has been suggested that the
presentation/format of some of the e-learning materials could be improved.
Summary of lessons learned/improvements for future projects:
-
4
Minimise use of armoured cabling
Confirm building specification and size earlier, reduce cable sizes where possible.
Rigorously check supplied equipment, use checklist.
Find ways to involve local workforce more.
Increase time allowed for design, ordering of equipment and installation (or reduce size
of project)
Consider taking duplicate tools.
Agree suitability of onsite equipment (e.g. ladders) prior to travel
Re-consider solar and battery technology (using this project as reference)
Communicate desired orientation of building to construction team in advance.
Consider format of e-learn→ing material.
Future Plans
The next phase of the project at Shiyala is the connection of the health output building and the
provision of the remaining 7 computers. This would take approximately 10 man days and would
involve the following tasks:
•
•
•
•
Wire lighting and sockets for administration building
Lay cable to health post and install health post distribution board
Wire lighting and sockets for health post
Install remaining 7 computers
Provisionally, this could take place (assuming the same team) in March or July 2013. July would be
preferable as there is less conflict with the academic year.
A further option would be return in July 2013 with an undergraduate team. Performing the same tasks
but involving undergraduates from engineering (2nd or 3rd years). This may be attractive from the
School of Engineering’s point of view as it could be used as a recruitment tool for prospective
undergraduates. This may bring about future collaboration and regular visits by the school. The
following advantages may exist if this option is taken:
•
•
•
•
The School of Engineering is more likely to provide travel funds if a recruitment opportunity
is created
Students may be able to fundraise
A shorter trip may be possible with more hands available
A successful 3rd year project run during 2012-13 may deliver improved Linux installation and
e-learning software on the computers, providing a better experience than the relatively crude
software in use now.
However, there would be many challenges associated with taking relatively inexperienced
undergraduates out:
•
•
•
•
5
Funding (flights, accommodation, transport within Zambia)
Liability/insurance
Recruitment – Just electrical engineering or expand to civil and mechanical?
Supervision load for Dan/Lee during the year (possibly could make this the 3rd year project
for 2-4 students?).
Acknowledgements
Dan and Lee would to thank everyone involved with making the trip happen. Special thanks go to
Prof. Judith Hall who arranged the trip and showed great patience in procuring the replacement
inverter! Thanks also to Alison, Buddug and Clara for their support throughout and to Jonathan, Dr.
Charles Msiska, Charles Banda and all of the Zambian workers for doing most of the hard work.
Thanks to everyone who helped and supported in the School of Engineering including Prof. Karen
Holford, Prof. Nick Jenkins, Dr Janaka Ekanayake, Dr Tracy Sweet, Paul Farrugia and Steve Mead.
Finally, thanks Debbie and Laura for their patience and support.
6
Appendix I – Initial Equipment Schedule
Note. The equipment schedule does not include all equipment taken. Also some items/suppliers/costs
were changed.
Zambia Solar Classroom: Equipment list
Last revision: LT 23/07/2012
Notes
The basic plan is for a classroom that can support up to 10 computers, each drawing 35W max. We also want to be able to supply 240Vac power to a nearby building, as well as proving some basic 240Vac power in the classroom for standard CCFL lighting, extractor fans etc.
Maximum 12Vdc load is 400W, maximum 240V load is 1500W. We have chosen a 48Vdc battery voltage to lower the maximum current seen in the design. Items highlighted in green will probably be sourced from Aleutia (RS part nos. given for reference). The remaining kit will
be sourced from RS or local electrical suppliers.
Item
PV panels, 1.2kW peak ouput total
PV charge controller, 48V battery capable
Batteries, 4x 12V 200Ah
48Vdc - 240Vac 1.5kW Inverter
48Vdc -12Vdc Converter, 500W
Main 4 Way Distribution Board
4 way panel assembly
63A 48Vdc 2 pole MCB Type B
12A 48Vdc isolator
240Vac 6 Way Distribution Board
Twin RCD 4 + 2 split board assembly
3A SPN MCB 240Vac Type C
6A SPN MCB 240Vac Type C
10A SPNMCB 240Vac Type C
12Vdc 4 Way Distribtion Board
4 way panel assembly
50A 12Vdc isolator
16A 12Vdc 2 pole MCB Type B
Cabling
16mm XLPE-SWA-PVC 3 core
10mm XLPE-SWA-PVC 3 core
10mm LSF Twin and Earth
6mm XLPE-SWA-PVC
2.5mm Twin and Earth
10mm LSF Earthing and Bonding Cabling 1 core
Accessories
Mounting board
Flexible conduit
Junction boxes
Conduit clips
Cable clips
Chocolate blocks
Armoured cable glands
Cable ferrules
Light Fittings
2 way light switch and back boxes, surface mount
1 way light switch and back boxes, surface mount
11W 240Vac CCFL with pendants
3W LED lamps for benches (12Vdc)
Earthing
Earth rod
Earth bar
Computers
T1 pro base unit (60GB SSD, Edubuntu)
Screens (12Vdc)
Mouse, keyboard, (speakers/headphones?)
Totals
Notes
approx 4kWh/day?
60A gives up to 2.9kW solar capacity (future expansion?)
4.8kWh with 50% charge-discharge cycle
Capable of 3kW peak (e.g. laser printer load)
Eliminates need for computer screen adaptors
No. or meters
4
1
4
1
1
Manufacturer
Xunlight
Morningstar
RS
Cotek
RS
Model Name
XR36-291-R2/R3
TS-MPPT-60
Gel Cyclic
SK1500-248
SD-500
Supplier
Aleutia
Aleutia
In Zambia
Aleutia
RS Online
Supplier part no.
Mass each (kg)
Total mass (kg)
491-267
12
4.2
61
5
1.2
48
4.2
244
5
1.2
689-5851
Cost ex VAT
Line cost ex VAT
650.00
2600.00
650.00
650.00
662
2648
470.00
470.00
185
185
Includes 100A incoming isolator
Checked DC rated up to 125V
Standard 100A incoming disconnector (cheap!)
1 Schneider
1 ABB
1 Square D
RS Online
RS Online
RS Online
528-9494
131-898
340-5076
0.5
0.5
0.5
0.5
35.72
31.98
10.34
35.72
31.98
10.34
Includes 100A incoming isolator and 2 x 30mA RCDs
1
2
2
1
Wylex
ABB
ABB
ABB
RS Online
RS Online
RS Online
RS Online
569-584
131-999
132-015
132-071
0.5
0.5
0.5
0
1
1
0.5
74.75
31.71
30.19
27.73
74.75
63.42
60.38
27.73
1 ABB
1 Square D
3 ABB
RS Online
RS Online
RS Online
453-974
340-5076
131-933
0.5
0.5
0.5
1.5
35.72
10.34
27.73
35.72
10.34
83.19
Includes 100A incoming isolator
Standard 100A incoming disconnector (cheap!)
Checked DC rated up to 125V
15m - 48Vdc PV Cntrllr to Panel, Batteries to Panel, Panel to Inv.
10m - 48Vdc supply to DC converter, 12Vdc supply to Panel
40m - 12Vdc supply for computers/LEDs
50m - 240Vac supply to admin block, supply for Panel
50m - 240Vac Lighting and Small Power
50m
Check suitable for 6 - 16mm cable
400mm
8 way 6mm
15 Prysmian
10 Prysmian
40
50 Prysmian
50
50
Edmundson Electrical
Edmundson Electrical
Edmundson Electrical
Edmundson Electrical
Edmundson Electrical
Edmundson Electrical
0
0
0
0
0
0
0.00
0.00
0.00
0.00
0.00
0.00
3
25
15
100
100
25
14
100
Edmundson Electrical
Edmundson Electrical
Edmundson Electrical
Edmundson Electrical
Edmundson Electrical
Edmundson Electrical
Edmundson Electrical
0
0
0
0
0
0
0
0
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
6
1
10
10
Edmundson Electrical
Edmundson Electrical
Edmundson Electrical
Ikea
0
0
15.00
15.00
150.00
150.00
2
1
Edmundson Electrical
Edmundson Electrical
0
0
0
307.9
269
155
30
2690.00
1550.00
300.00
11826.57
10
10
10
7
Appendix II – Solar panel output simulation
Zambia solar school project.
8
Appendix III – Equipment Manuals/Data Sheets
Available on request: Email ThomasL62@cf.ac.uk
Note. A hard copy of all available manuals and data sheets was left in the Electrical Switchroom at
the new Shiyala Education Facility..
9
Appendix IV – As-Installed Electrical Schematic