Solar panels, which heat the climate, can be? | Science | News | The sun

CThis is a question that many researchers have been asking themselves in recent years because its prototype is undeniable: a fraction of the sun’s energy reflected by the Earth’s surface is actually greater than that of solar panels. On average, the Earth reflects 30% of the sun’s light back into space (this is called the “albedo” of 0.30), although it varies from place to place – 80% of fresh snow, 40% of deserts, 25% of meadows. And 12-15% in the wild. As for solar panels, that is Reflects only 10%, The rest are converted into electricity (about 15%) or dissipated into heat (75%). Keep in mind that even the role of electricity will inevitably end up hot.

So it is obvious that solar panels have a warming effect, at least locally. But is this enough to nullify their environmental benefits, i.e. produce electricity (or almost) without GHGs? There are two things to note here: first, the potential “hot island” effect, which will be basically local; Then the potential climate effect on a large scale.

There is no doubt that solar power plants can create tropical islands, especially when installed in places with high albedo such as deserts – as this often happens, because deserts are the perfect places to increase the production of solar panels. Thus, an American study Released in 2016 Scientific reports Found a difference of 3-4 C overnight between a solar power plant and a desert area a few hundred meters away. A Chinese study was obtained The results went in the same direction Next year.

Keep in mind that this does not always seem to be the case French works In the city and in the heating panels (converting heat into electricity, not light, it is very efficient), these reduced the temperature by an average of 0.2 to 0.3 C. So, let’s keep in mind that the end result depends on the environment in which you are installing the solar panels – a black panel that replaces black asphalt singles, clearly not like a black panel. It covers a clear surface.

It is not clear whether “solar farms”, as they are called south of the border, can promote tropical islands, which have the ultimate effect of warming the climate. First, Simulations provided in 2013 During a conference of photovoltaic experts, if the temperature in the middle of a large solar power station is almost 2 C higher than the ambient temperature of 2.5 m above the ground, the difference dissipates very quickly, no longer measurable at an altitude of only 5 m, and the temperature difference disappears completely at night. This suggests that the effect will be more localized, not global.

Other works focus on the overall effect of solar panels, not only from the albedo view, but also on the GHGs that solar panels avoid. In Nature – Climate change In 2015, Researchers at Boulder University in Colorado concluded that “overall, the global climate change that can be triggered by the use of solar panels is small compared to the expected (1) climate change from fossil fuels.” So these panels are “profitable” from a climatic point of view, taking into account even the bulk of the remaining solar radiation on Earth.

However, this energy source may have a significant influence on the climate, but not in a positive way. If solar energy projects ever really reach the baronic ratio, the “regional” effects could be so strong that they are destabilizing the climate on a planetary scale. For example, Modeling work released in 2018 Science If we cover 20% of the entire Sahara (!) With photovoltaic panels, it would increase the surface temperature in this desert to about 2 C and be large enough to change the atmospheric circulation. The result will be increased rainfall in the Sahara and the Sahel (the southern semi-arid zone of the Sahara), which will be favorable for vegetation. This then increases the rainfall (because the plants “take” a lot of water from the earth and “sweat” through their leaves), which brings in more plants, which the earth absorbs even more energy. Sun, and so on. These effects are described as “beneficial” in the study, and the reason for this is easy to understand, but it shows that in at least some situations, truly gigantic solar power plants can disrupt the climate on a large scale.

A Another study on the same topic Its part decided that a solar power plant covering 20% ​​of the Sahara would actually cause planetary effects (drought in the Amazon, warming in the Arctic, etc.). This is a simple modeling for now, so it remains to be seen whether others will come to comparable conclusions – and then, if these predictions change in reality – but yes, in principle we can say that solar power plants are possible if they are beautiful and built in a specific environment, with global implications for the climate. Mr. As Le May requested, heating it is not necessary, but it can theoretically “disturb” it.