cost per kWh [RE-wrenches]

[Hugh Piggott]

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At 1:23 PM -0700 30/5/03, Bill Brooks wrote:
>Hugh and Eric,
>
>I think the fill factor of the array is critically important when making
>assumptions about how far off max power a PV-battery system operates. I have
>nearly 5 years of experience with my own battery-based, grid-tied PV system,
>and I have to say that the majority of the energy is delivered at voltages
>very close to max power voltage.

That's reassuring.

>The max power voltage of most 12-volt crystalline
>modules at typical operating temperatures is 14 to 15 volts, not 17.6.

So what power output adjustment do you expect to make to nominal Pmax 
at that voltage?

>Stand-Alone systems are different and depend on the state of charge of the
>battery.

Here in Scotland we do not use air conditioning and there is a good 
chance that the battery voltage will be up on a sunny day.  If not, 
then the power will be going direct to the inverter, which is good 
news for system efficiency.

>
>I think the correct method is to use watts and an appropriate adjustment
>factor rather than amps.

What adjustment factor(s) would you apply to arrive at energy into 
the battery, using sun hours (kWh/m2) and the STC Pmax power data?

Thanks.
-- 
Hugh

hugh at scoraigwind.co.uk
http://www.scoraigwind.co.uk/

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