Solar panel temperature is one of the important factors that affects how much electricity your panels will produce. It's ironic – but the more sunshine you get, the hotter the panels get and this in turns counteracts the benefit of the sun.
In some cases the heat factor can reduce your output by 10% to 25% depending on your specific location.
Of course, not all solar panels are affected by heat equally and luckily some do much better at coping with the heat than others. Here's what you need to know.
If you look at the manufacturer's data sheet you will see a term called "temperature coefficient Pmax". For example the temperature coefficient of a Suntech 190 W (monocrystalline) solar panel is –0.48%. What this means is that for each degree over 25˚C … the maximum power of the panel is reduced by 0.48%.
So on a hot day in the summer – where solar panel temperature on the roof might reach 45˚C or so – the amount of electricity would be 10% lower.
Conversely, on a sunny day in the Spring, fall, or even winter – when temperatures are lower than 25˚C – the amount of electricity produced would actually increase above the maximum rated level.
Therefore, in most northern climates – the days above and below 25˚C would tend to balance each other out. However, in locations closer to the equator the problems of heat loss could become substantial over the full year and warrant looking at alternatives.
Note:For those of you who want to use their solar panels to charge their RV or boat batteries – you'll will need to make sure that the voltage produced by your panel (under high heat scenarios) will be sufficient to recharge your battery – so it's best to order higher voltage solar panels to offset the temperature losses – and also keep the panels clean for maximum output.
Some Solar Cells Respond to Temperature Changes Better than Others
The solar panel temperature affects the maximum power output directly. As solar panel temperature increases, its output current increases exponentially while the voltage output is reduced linearly. Since power is equal to voltage times current this property means that the warmer the solar panel the less power it can produce. The power loss due to temperature is also dependent on the type of solar panel being used.
Typically, solar panels based on monocrystalline and polycrystalline solar cells will have a temperature coefficient in the –0.44% to -.50% range.
Amporphous Silicon does a bit better. For example, the Sanyo HIT hybrid cells and bifacial cells, which consist of a layer of monocrystalline silicon covered with a thin coating of amorphouse silicon have a lower temperature coefficient of –0.34% - making them another good choice for people looking for high efficiency solar panels in areas closer to the equator.
The best so far in terms of dealing with high temperatures are the Cadmium Telluride solar panels – with a temperature coefficient of –0.25%. However, while they are good with dealing with temperature changes – they are not as efficient at converting sunlight into electricity.
Newer technologies such as CIGS and some of the 4th generation solar cell technologies being developed show show promise of also being less affected by the temperature – but we have to wait until their datasheets are published to know for sure.
Because of the problem of loss of electricity as a result of heat buildup – most installers make sure it is possible for air to flow above and below the solar panels to help keep them cool.
-Try to use light colors under the panels.
-Stay away from black back panels.
-Water cooling - Run your potable water under the panel (maybe in line with solar hot water system) with a heat exchanger.
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