alt.energy.homepower

Hi David;

David Williams < @ > wrote:

> -> > I know a 100w solar panel puts out ~20v no load. so
> -> > that's 100w/20=5 amps theoretically in full sun.

> -> No. 5 amps is a load, so the voltage will be lower
> -> than 20V at a 5 amp load.

> -> Graham

> If the no-load voltage is 20 volts, then when the
> output power is highest ( . the load's resistance
> equals the internal resistance of the panel),
> the output voltage will be only 10 volts. If the
> power in the load is then 100 watts, the current
> must be 10 amps.

This would be true if the cell resistance was constant.
It isn't. The internal resistance is highly non linear.

This is why PV panels with an open circuit voltage of
about 20V have a Maximum Power Point of about 17V.

> dow

Duane

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