1. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 1 2-7. What about battery additives that are supposed to “rejuvenate” old batteries. Do they work?

2. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 2 How are batteries damaged by excess discharge? When a battery discharges the plates swell. The deeper the discharge the more the plates swell. Batteries that are not designed for deep discharge have flat plates that have the active material pressed into pockets in the plate. When the plates swell greatly due to deep discharge, some of the active material is pushed out of the pockets and falls to the bottom of the battery causing loss of capacity and possible shorting of cells. Batteries that are designed for deep discharge have plates that have the active material wrapped in porous membranes to prevent the swelling from causing the active material to fall off. This adds considerably to the cost but increased battery life.

3. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 3 Choices for Solar Use Open cell batteries provide the best value and longest life but electrolyte levels have to be checked and water added when needed Tubular cell, deep discharge batteries provide the longest life and should be used where access for replacement is expensive or very difficult Valve regulated, sealed batteries are only recommended where there is no one to properly maintain an open cell battery Worst choice is an automotive type “maintenance free” battery.

4. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 4 Increasing battery voltage Add cells or batteries in series. Increments may be 2V (single cells for large batteries), 6V (three cells in one case – medium sized batteries), 12V (six cells in one case, smaller batteries). No problems usually develop because of series connections though a battery with a shorted cell can create overcharging conditions for the rest of the cells because the lower battery voltage that results from a shorted cell makes the controller think that the battery still needs charging so the charging current is not shut off when the good cells do come to full charge. The result is excessive water loss from the battery, a definite symptom of a shorted cell in an SHS battery along with voltage that is lower than expected.

5. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 5 Increasing Ah capacity Put in a larger battery. It is always preferred to use a single large battery than to connect batteries in parallel It is possible to parallel identical batteries just as it is possible to parallel panels. However never should more than two batteries be placed in parallel and even then do not expect as long a life as a single larger battery. If one cell of either battery loses capacity, both batteries may rapidly develop sulfation problems. Note that many battery manufacturers void battery warranties if more than two are paralleled.

6. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 6 Battery Safety Most injuries relating to batteries are the result of dropping them or being hurt somehow by their weight. Do not carry batteries by the connections, always support the battery from the bottom or sides of the case. Preferably use a special carry strap made for the purpose. For large batteries share the load with another person. Many batteries have built in handles. Use them For open cell batteries, note that the electrolyte is dilute sulfuric acid and can cause mild chemical burns and is toxic if swallowed. If the acid gets into your eyes, immediate flushing with water is vital to avoid eye damage. For that reason, keep a full bucket of water nearby when working with batteries and battery acid. Be sure cell caps have clear ventilation holes. A plugged ventilation hole will cause pressure build up in the cell and will cause the battery case to swell and may cause damage to the battery. Never lay tools on top of the battery. A short circuit could occur and may damage the battery, cause an explosion or cause burns. Do not smoke around batteries that are charging. Explosive gas is present in the cells. Do not take the caps off battery cells when charging.

7. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 7 Don’t lay tools on batteries!

8. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 8 2-8. Appliances

9. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 9 Appliances suitable for SHS High efficiency DC lights. Currently CFL type lights have the highest efficiency but LEDs are getting close and provide the major advantage of simplicity and very long life plus they cause no radio interference. DC Appliances (battery operated radio/boom box, DC Televisions) Small to medium AC Appliances (videos, fans, refrigerators, washers)

10. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 10 Appliances not reasonable for SHS use High demand, low value appliances such as electric fry pans, electric tea kettles, coffee makers, toaster ovens High demand major appliances such as electric cooking stoves, electric dryers, electric water heaters and air conditioners. If you make the SHS big enough, you can run any household appliance, but the enormous cost of the large solar installation to run the appliance usually is not worth it.

11. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 11 Appliance Energy Comparison B&W TV ≈ 1 10W light Desk fan ≈ 5 lights Color TV ≈ 7-10 lights Ceiling fan ≈ 10 lights Full Size Refrigerator ≈ 25 lights Chest Freezer ≈ 40 lights Room air conditioner ≈ 75 lights

12. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 12 Converting DC to AC Inverter characteristics –Type of output wave shape (square wave, modified sine wave, sine wave) must fit the type of appliance being powered.  AC motors usually require sine wave inverters  Electronic equipment usually works well with modified sine wave inverters  Square wave inverters should not be used. –Continuous power rating –Surge power rating (for motor starting mainly) –Protection against over voltage, under voltage, over current, over heating, reverse polarity

13. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 13 Why not use inverters with all SHS? Cost (up to US$1 per Watt capacity) Power loss (10-15%) Safety (120/220V can be lethal) AC appliances tend to be much lower in energy efficiency than DC appliances made for solar systems Easy to overload systems by plugging in more appliances Probably the best approach is to have a dedicated inverter for each AC appliance. That ensures the right type of inverter is used and the losses are minimized. Be sure that the inverter is turned off when the appliance is turned off.

14. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 14 What about a refrigerator or freezer? Around 500 Wp of panel capacity needed just for the refrigerator. More for a freezer. A sine wave inverter is needed with sufficient surge capacity to start the compressor and sufficient continuous capacity to run the compressor. Typically the surge may be 400 Watts for 5 seconds then a running requirement of 150 Watts continuously. This varies with the size of the refrigerator or freezer.

15. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 15 What about power for a video system About 200Wp of panel is needed just for the video (color TV screen and video player) Modified sine wave inverter of 150 W continuous rating dedicated to powering the video player and associated color TV.

16. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 16 2-9. Wiring

17. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 17 Characteristics of wiring Number of copper conductors per cable (1 or 2 needed – never use aluminum wire) Stranded or solid wire Type of insulation (indoor only, outdoor, direct burial) Size of conductor (mm 2 or AWG) Length of wire

18. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 18 Choose the correct insulation If indoor type wire is used to connect to the panels, the insulation will crack and fall off after a few years because of ultra-violet degradation of the plastic by sunlight. If you must use indoor wire, put it inside a plastic or metal pipe (solid plastic or metal conduit or flexible water pipe) to protect it from the sun. If you bury the wire, always use wire with insulation certified for burial since earth fungus and moisture will gradually cause other types of insulation to fail. If non- burial wire must be used, it has to be placed inside a plastic or metal pipe before burial and the open ends of the pipe sealed with silicone rubber to prevent water and insect entry. Burial type wire will be damaged if exposed to sunlight. Where it comes out of the ground it should be enclosed in plastic pipe and sealed with silicone rubber at the end of the pipe.

19. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 19 Connections Because 12V is very low pressure electricity, the wiring connections must be of very low internal resistance. Otherwise the voltage drop will be excessive. The connections need to be ones that will not change internal resistance over time due to corrosion or loosening Only screw type connections or properly soldered connections should be used. Note that most field soldered connections are “cold” solder joints and are not adequate. Solder must be fully melted and flowing onto the wires.

20. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 20 Improper connections Twisting wires together will quickly result in high voltage drops. DO NOT USE Using “twist lock” connectors that twist the two wires together in a plastic holder will be better than just twisted wires but will gradually increase in voltage drop. DO NOT USE Crimped lug connections are ok only if the proper tool is used by a person well trained in the proper technique for crimping. Rarely are crimped lug connections made in the field good for more than a year or two. DO NOT USE

21. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 21

22. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 22 Switches Switches often greatly increase in voltage drop with age, particularly cheap “slide contact” type switches commonly used for 220V installations. For long life, use snap action “toggle” type switches that use a spring to snap the contacts together, preferably a type that is designed for DC use.

23. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 23 Check Switches Annually Voltage drops on switches should be checked at least once a year. To do that, turn the switch on so the load is operating and measure the voltage across the switch terminals. It should not be over 0.05V. If the cheap “slide contact” switches are used, they should be replaced every time the battery is replaced to ensure that the voltage drop does not become excessive.

24. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 24 2-10. Installation of SHS

25. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 25 Panels Free of shade 0900-1500 At least 60 mm (2.5”) of space behind the panel for ventilation, preferably 100mm (4”) Facing the south and tilted at about the latitude angle but greater than 10° Mounting uses non corroding screws or bolts preferably of marine grade stainless steel Mounting meets the requirement for strength under storm conditions Wire fastened to the mount in a way that does not put a strain on the connection boxes. Terminal screws include lock washers and are tightened properly Wire is big enough to keep losses at less than 0.5V between the panel and battery at maximum current from the panel, usually 10AWG or 4mm 2

26. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 26 Battery Sits level on a solid surface that will not deteriorate if exposed to acid (not wood or metal) Cool site not exposed to the sun Good ventilation for disposal of explosive gasses Covered to reduce dirt accumulation on the top of the battery but readily accessible for service Located as close to the loads as practical to minimize wire lengths. Located in a place not likely to be a play area for children.

27. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 27 Controller Must be within 2 meters (6 feet) of the battery and preferably less Located in a cool place with adequate ventilation to carry away generated heat Firmly affixed to the building with non-corrosive screws

28. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 28 Appliances Place lights where the user prefers Arrange wires so the minimum length is needed Use the right size wire to fit the length used. Usually AWG 12 or 2.5mm 2 Mount lights for maximum lighting of the area desired by the user with minimum loss of light in other directions Use non corrosive screws for mounting. Do not hang lights by connecting wires (unless the light is designed for that type of mounting) or tie lights to beams with cord. Provide a connection point in a convenient location for radio or B&W TV use.

29. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 29 Fuses Fuses are intended to protect components (mainly the controller) and to prevent overheating of wiring and possible fires. Fuses must have low internal resistance that remains low for the long term. Glass type cartridge fuses have not worked well with PV systems and are not recommended. Automotive type clip-in fuses have worked satisfactorily and are recommended Circuit breakers have not worked well in small PV systems and are not recommended. At least one fuse located near one of the battery posts is best. It should have an Ampere capacity about the same as the maximum safe carrying capacity of the load wiring. For larger systems with many circuits or systems with several larger loads, a fuse may be needed for each load circuit that limits the current to the safe capacity of the wiring in that circuit. Safe capacity is the wire’s rated “ampacity”.

30. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 30 Wiring Ensure wire sizes are appropriate for the load and length of wire Install an automotive type plug-in fuse in the wire near one battery connection All wire junctions and connections should use screw type connectors with non-corroding screws. Fix wires to the building with clips at least once per meter (3 feet). Place clips within 15 cm (6") of all connections Place clips within 15 cm (6") of each side of a right angle bend in the wire Avoid circuit breakers, use automotive fuses instead.

31. e8 / PPA Solar PV Design Implementation O&M Marshall Islands March 31-April 11, 2008 31 Lightning Protection For SHS where there is no AC power from an inverter, no grounding or specific lightning protection is needed. Where there are AC appliances, the inverter should be properly grounded and usually so is the negative side of the battery circuit. All connections to earth should be at the same spot. Some believe that a large copper wire connected to the panel frame and run directly to the earth connection adds lightning protection. There is no clear evidence whether this works or not.