Sunday, May 23, 2010

Heat restrains PV harvest

23 May : The photovoltaic harvest is very good at the moment, we are ahead of the expectation calculated by the JRC PVGIS site. I notice that although the sun is getting higher in the sky and showing for longer periods, our best score is still no more than about 22-23 kWh per day.
    The common view is that PV performance declines if the panel surface gets hot - this seems to be true! Today for example, our mini weather station which records surface temperatures has gone right off the scale - way above 40º, with air temps touching 30º in mid afternoon! For the first time.

I am guessing that the PVGIS might have a compensation factor for just this, as it shows June's harvest prediction to be poorer than May or July. How can that be?

Our best ever day was May 11 with over 24 kWh, but that day was notable for having cold temperatures (North Wind). I am not complaining, as it is only the 23rd May and we have already reached the PVGIS expectation for May. But the 'competitive' in me would still like to do better in June and July.
    Meanwhile today, we have burst through the 1600 kWh barrier at a gallop (this is for 'annual PV generation') That puts us well more than half way to our target of 2800, and with the rest of May, June, July, August and September (to meet our PV-Anniversary of October 1, we look easily positioned to get past 3000.

When the long months of winter come, and I have the depressing sight of the PV getting worse again day by day, I shall be compensated by the interest provided for me in the experiment to charge the ground below with hundreds of summer time kilowatt hours of solar heat, to see how the heatpump fares with next winter's heating loads.

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