CIt’s a question many researchers have asked themselves in recent years, because its premise is undeniable: the share of the Sun’s energy that is reflected off the Earth’s surface is actually greater than that of solar panels. On average, Earth reflects about 30% of sunlight back into space (it is said to have an “albedo” of 0.30), although this varies from place to place – it is about 80% for fresh snow, desert is in 40%. , 25% in grasslands and 12-15% in forests. In the case of solar panels, it is only 10% that is reflectedThe remainder is either being converted into electricity (about 15%) or dissipated into heat (75%). Note that part of the electricity will also inevitably dissipate as heat when expended.
So it’s clear that solar panels can have a warming effect, at least locally. But is this enough to cancel out their environmental benefits, namely the fact of producing electricity without (or almost) GHGs? There are two things to consider here: first, a potential “heat island” effect, which will essentially be local; And then the massive potential climate impact.
There is no doubt that solar power plants can create heat islands, especially when installed in places with high albedo, such as deserts – which is often the case, as deserts are the perfect places to maximize the output of solar panels. . Thus, an American study published in 2016 scientific report A difference of 3-4 °C was observed overnight between the solar power plant and a desert area a few hundred meters away. received a Chinese study results that went in the same direction Next year.
Note that this doesn’t always seem to happen because french works suggested that in the city and with thermal panels (which convert heat to electricity, not electricity, which is clearly more efficient), these temperatures drop by 0.2 to 0.3 °C on average. So let’s keep in mind that the final effect depends a lot on the context in which you install the solar panels – a black panel replacing black asphalt shingles is clearly not the same thing as a black panel. which covers a clear surface.
But while “solar farms”, as they are called south of the range, may be promoting heat islands, it is not at all clear that they have the ultimate effect of warming the climate. First, Simulation presented in 2013 During a conference of photovoltaic experts concluded that if the temperature at 2.5 m above the ground in the middle of a large solar power plant was about 2 °C higher than the ambient, the difference very quickly narrowed, no longer Measurable only at a height of 5 meters, and during the night the temperature difference completely disappeared. This suggests that the effect will be very local, not global.
Other work has focused on the overall impact of solar panels, not only from the point of view of albedo, but also of the GHGs that solar panels avoid from us. In Nature – Climate Change in 2015In , researchers from the University of Boulder, Colorado, concluded that “overall, (…) the global climate changes potentially induced by the use of solar panels are smaller than the climate changes expected from fossil fuels”. So it looks like these panels remain “profitable” from a climate point of view, taking into account the large part of the solar radiation that remains on Earth.
However, there is still a possibility (at least theoretical) that this source of energy could have a significant, and not necessarily positive, effect on the climate. If solar power projects do indeed reach Pharaonic proportions, the “regional” effects could be so strong that they disrupt the climate on a planetary scale. for example, Modeling work published in 2018 Science indicated that if we covered 20% of the entire Sahara (!) with photovoltaic panels, it would increase the surface temperature in this desert by about 2 °C and an area large enough to alter atmospheric circulation. One consequence of this would be increased rainfall over the Sahara and the Sahel (the semi-arid region south of the Sahara), which would favor vegetation. This would then add to rainfall (since plants “take up” a lot of water from the earth and “sweat” through their leaves), which would bring in even more vegetation, which would absorb even more energy. Earth. Sun, and so on. These results are described in the study as “beneficial”, and it is easy to understand why, but show that at least in some circumstances, giant solar power plants can indeed disrupt the climate on a large scale. Huh.
a Another study on the same topic For its part it was concluded that a solar power plant covering 20% of the Sahara would have a literal effect (droughts in the Amazon, increased warming in the Arctic, etc.). This is just a simple modeling at the moment, so we’ll have to see if others arrive at comparable results – and then, if these predictions turn into reality – but let’s say yes, it is theoretically possible that solar power Plants, if they are arboreal and built in a particular context, have a global impact on the climate. Not necessarily by heating it, as Mr. Le May requested, but it could theoretically “disturb” it.