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Why solar PV panels don't work so well in the heat
Posted by Chris Rudge on 19 July 2010 at 9:32 am
During these last few weeks of hot sun, which are a welcome change from the rain of previous few years, we have been getting calls from customers asking why the output from their solar PV panels is down, even though there is bright sun beaming down onto it.
The simple answer is solar heating!... Unlike solar thermal systems which rely on the sun's heat to do their work, solar PV works on light, and would like to stay as cool as possible. You'll notice your solar PV panels will produce as much output on a clear sunny winter's day as in the summer, even though the sun is lower in winter.
In winter your solar PV panels will be far colder, maybe almost zero degrees, which will improve their efficiency. In the summer sun, the solar PV module temperature will soar far over the Standard Test Condition (STC), rating of 25 degrees C, causing output to slump a little.
A recent example showed our office solar PV system drop off by 10% in the recent 30 degree plus days. So dont worry that a module is failing. Your system will perk up when the weather is cooler.
Photo: Wichita Renewable Energy Group
About the author: Chris Rudge is a qualified electrician who specialises in renewable energy.
If you have a question about anything in the above blog, please ask it in the comments section below.
Comments
3 comments - read them below or add one
It will be interesting to see the application of thin film PV. Ive noticed our installations are providing greater power outputs now the temp has dropped on a bright day.
GM RenewablesComment left on: 29 September 2010 at 5:26 pm
PVT panels can increase output of the PV side of the panels by cooling.
Increases in efficiency of up to 40% are possible and there is an enormous supply of heat, ideal for swimming pools for instance.
www.gm-renewables.co.uk have full details.
Jayhawk International LtdComment left on: 20 July 2010 at 1:10 pm
I am very pleased to read this statement by Chris about the drop in efficiency during hot weather of PV panel installations.
We are soon to introduce a PVT panel, German design and German quality as you would expect.
In their 2 years of factory testing and in the TUV testing it was found that a 30% drop in efficiency could be shown when outside tempertures were 30C +
The PVT panel provides electricty from the top and heated water underneath but not to tempertures of 70c but 40c as the lower the temperture flowing across the back of the PV panels, the higher the efficiency increases.
The ideal installation for the PVT panel is when the swimming pool needs to be heated and any comercial building where a pre heated water is required in volumes. Like a Brewery
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