[RE-wrenches] PV into a resistor: please advise

Mick Abraham mick at abrahamsolar.com
Sat May 19 12:35:39 PDT 2012


Hi, Wrenchies~

Kindly educate me regarding PV behavior when the load is a resistor. Here's
a hypothetical situation:

* Eight 250 watt PV modules (60 cells per module), all connected in series
for "peak" ratings of 240 volts DC & 8.3 amps

* Lab type cell temperature & illumination so that the eight would truly
pump 2,000 watts *into an ideal load*

* A 240 volt AC heating element designed for 2,000 watt heat dissipation at
240 volts AC...that's about 29 ohms resistance for the heat element

* Connect the PV string to the heat element, with nothing in between except
a fused disconnect.

In the above situation, would the resistance of the heating element be all
that's needed to force the PV array to operate near the "peak" wattage?
Would the heater actually get 2,000 watts to turn into heat?

+++++++++++++++++++++++++++

Now consider the same cell temperature but half the illumination. That's
similar voltage but half the amps at peak wattage. If this is sent into the
same 29 ohm
resistor--again with no intervening electronics, could we count on 1000
watts of heat?

If the answers come up "no", would the power throughput be helped by a
SolarConverters style MPPT pump controller (Linear Current Booster kinda
thing), assuming that one could be found to operate in the 240 volt range?

Thanks & Jolliness,

Mick Abraham, Proprietor
www.abrahamsolar.com

Voice: 970-731-4675
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