As summer gets into full swing, it’s natural to assume the conditions are perfect for generating solar power. But it turns out that cooler days in spring can provide better conditions.
PV systems use solar panels to convert light into electricity. While longer hours of sunshine can increase their output in summer, the higher temperatures are detrimental to the generation of electricity. A typical solar panel loses about 0.5 per cent of its maximum power with every additional degree Celsius, which is known as its temperature coefficient.
So why is heat a problem? Electricity is generated when photons carried by sunlight hit electrons on a solar panel, transferring their energy in the process. The photons raise electrons from their ground state to a high-energy state. Over the hot summer, electrons would already have plenty of energy normally and do not gain as much from sunlight. This reduced energy gain means that less electricity is generated.
A way to address this problem is to install solar panels just above the roof so that airflow above and below keep them cool. In more extreme climates, novel materials might be needed to counteract the heat.
Humidity can also be problematic, as water molecules in the air diffuse sunlight. The angle the panels are placed at should be changed throughout the year to directly face the sun: a shallower angle is better during summer, a steeper angle is better in spring when the sun doesn’t rise as high.
In 2015, Germany set a world record with a peak solar power of 25.8 GW – in mid-April.