Solar Panels.
Panels DO NOT need direct sunlight to operate. They will work less optimally but still work on overcast days (we get very many of these in my country)
Solar panels are a constant current generator. An 8amp panel in sunlight will generate 8amps at 0v (when short circuited) up the max Vmp of the panels.
Panels are available in a variety of voltages expressed in Open Circuit voltage and Max Power voltage. A single cell generates about 0.5 volts. A nominal ‘12v’ solar panel will in fact be about 18v Vmp so that it can charge a 12v battery up to its bulk voltage and to factor in losses.
So a typical 12v panel will have at least 36 cells in series.
In the not distant past of 5-10 years ago the only thing that was affordable on a budget were cheap Chinese 12v panels. These were good because they could be used easily with a 12v battery and cheap PWM controller.
Larger panels are available in ever increasing sizes with slightly different layouts and colours. The newest developments are half cell panels to reduce shading issues and double sized panels for use on stand alone mounts which make use of reflected light.
Panels DO NOT need direct sunlight to operate. They will work less optimally but still work on overcast days (we get very many of these in my country)
Solar panels are a constant current generator. An 8amp panel in sunlight will generate 8amps at 0v (when short circuited) up the max Vmp of the panels.
Panels are available in a variety of voltages expressed in Open Circuit voltage and Max Power voltage. A single cell generates about 0.5 volts. A nominal ‘12v’ solar panel will in fact be about 18v Vmp so that it can charge a 12v battery up to its bulk voltage and to factor in losses.
So a typical 12v panel will have at least 36 cells in series.
In the not distant past of 5-10 years ago the only thing that was affordable on a budget were cheap Chinese 12v panels. These were good because they could be used easily with a 12v battery and cheap PWM controller.
Larger panels are available in ever increasing sizes with slightly different layouts and colours. The newest developments are half cell panels to reduce shading issues and double sized panels for use on stand alone mounts which make use of reflected light.
However things have moved on a lot. Cheap MPPT controllers are widely available to suit all budgets. The most efficient thing to do is find surplus 250-300w domestic panels and use them with an MPPT controller. The higher voltage battery you use the lower amp rated charge controller you need.
The Solar manufacturers are ranked into ‘Tiers’ Panels from Tier one manufacturers have the longest warranties and there are plenty available so there’s no really need to buy anything else unless you find something very cheap.
It is not worth buying cracked solar panels however cheap they are. It might be tempting but don’t do it. The only way to repair them is to use an expensive optically perfect glass adhesive. Which works out more costly than just buying working panels. The cracks in the glass cause internal shading so they work okay at exact solar noon but no other time.
Second Sol is a good source for finding large amounts of new or second hand panels at cheap prices. Especially if bought it quantities of more than 100 for a community or group project.
Comments
Post a Comment