A brutal heat wave has been burning Europe for more than a week. Some countries like France or UK have reached historic records of high temperatures (40ºC) and hundreds of hectares have burned in the south of the continent in countries such as Spain, Portugal or Greece. This is a climatic episode never seen before. In the midst of all this, Germany produced a record amount of electricity from solar energy a few days ago: some 38,174 megawatts were generated from solar panels and more is expected in the coming days.
many people are thinking that, with these extreme waves, they will be putting on their boots in the solar sector. Anyone would say that the hotter they are, the better they will work. It is not like this. Actually the extreme heat is hampering their work.
Do they work better or worse on hot days? The truth is that these record amounts of energy could have been much higher if the temperatures had been somewhat lower. Counterintuitively, warmer, sunnier days do not equate to more energy, as rising temperatures actually hinders the ability of solar panels to collect it. Most panels are tested at a temperature of 25ºC, which is ideal. But above this threshold, no matter how bright the sun is, the efficiency drops.
“A solar panel is a bit like the silicon chip inside your computer, if it gets too hot, it doesn’t work as well,” explained resource scientist Ray Wills in this ABC News article.
Why? To understand this loss of efficiency, you have to know how the panels themselves work. As explained in this Euronews report, these absorb sunlight with their photovoltaic cells, and the photons absorbed by the panels release electrons from their atoms and form an electrical circuit within the panel’s semiconductors, generating a flow of electricity. But the hotter the panel, the greater the number of electrons that are already in the “excited” state. This reduces the voltage that the panel generates and decreases its efficiency.
And it’s pretty serious. High temperatures can decrease the efficiency of solar panels between 10 and 25%, according to CED Greentech data. And, for each additional degree Celsius, its efficiency drops by 0.5%, according to Solar.com.
Well above the optimal level. Following the calculations and taking 25ºC as the optimum level (the temperature of the panel itself, not the atmospheric temperature), on a 45°C day, the panel would be expected to be at least 75°C. If the panel is 50°C warmer than optimum, output power will decrease by about 25%. If it’s 10°C higher than normal, you’ll have 5% less performance, which isn’t much, but something to consider. Now imagine what can happen in the middle of a heat wave like the one we are currently experiencing.
The actual situation. Added to this is that in extreme heat conditions, many more people will turn on their air conditioners, which will increase the demand for electricity. Nowadays, there is large-scale investment by governments in home batteries that capture energy generated by rooftop panels, with the aim of reducing household energy bills. Will this heat be bad for those bills? Yes.
It should also be noted that there are thermal solar panels, which would not be affected by the increase in heat. It is necessary to differentiate between the different types of solar energy production: solar photovoltaic and solar thermal. As its name suggests, solar thermal takes advantage of the sun’s heat and works like a coal-fired power plant: it boils water and generates steam. But these panels are much rarer, especially in homes, and are considered less reliable for generating electricity.
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