Solar panels that heat the climate, can it? | Science | News | The sun

Solar panels that heat the climate, can it?  |  Science |  News |  The sun

CThis is a question that many researchers have recently asked themselves, because its introduction is undisputed: part of the sun’s energy reflected on the Earth’s surface is, of course, larger than solar panels. On average, the Earth reflects 30% of the sun’s light back into space (it is said to have an “albedo” of 0.30), although this varies from place to place – 80% for fresh snow, 40% for desert, and 25% for grassland. 12-15% in forests. In the case of solar panels, that is Only 10% reflected, The rest is either converted to electricity (approximately 15%) or heated (75%). Note that when even a fraction of the electricity is expended it will inevitably end up hot.

So it is clear that solar panels can be heated at least locally. But is this enough to undo their environmental benefits, i.e. to generate electricity (or at most) without GHGs? There are two things to note here: first, the potential “hot island” effect, which must be local; Large-scale climate impact.

There is no doubt that solar power plants can create hot islands, especially when it is placed in high albedo areas such as deserts – this often happens because deserts are the best places to maximize the production of solar panels. Thus, an American study Published in 2016 Scientific reports A difference of 3-4 C was found overnight between a solar power plant and a desert area a few hundred meters away. Received a Chinese study The results went in the same direction Next year.

Note that this does not always seem to be the case French works In the city and in thermal panels (converting heat into electricity, not light, it is more efficient), this reduced the temperature by an average of 0.2 to 0.3 to C. So, keep in mind that the end result depends a lot on the context in which you install the solar panels – a black panel that replaces black asphalt shingles is clearly not the same as a black panel. Includes clear surface.

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While the so-called “solar farms” south of the border can promote hot islands, it is not clear what the ultimate effect of warming the climate will be. First, Simulations presented in 2013 A conference of photovoltaic experts concluded that if the temperature in the middle of a large solar power plant is 2 C higher than the ambient temperature of 2.5 m, the difference dissolves very quickly and can be measured at an altitude of only 5 m, and at night the temperature difference disappears completely. This indicates that it will be localized, not globally.

Other activities focus on the overall impact of solar panels, not only from the albedo point of view, but also on the GHGs that solar panels exclude us from. In Nature – Climate change In 2015, Researchers at Boulder University in Colorado concluded that “overall, the potential for global climate change due to the use of solar panels is very small compared to the expected (() climate change from fossil fuels.” So even considering the large share of solar radiation left on Earth, these panels remain “profitable” from a climate point of view.

However, this source of energy is likely to have a significant influence on the climate (at least theoretically). If solar energy projects ever reach true pharaonic proportions, the “local” impacts could be so severe that they would wreak havoc on a planetary surface. For example, Modeling work published in 2018 Science If we covered 20% of the entire Sahara with photovoltaic panels, this would increase the surface temperature in this desert by about 2 C and increase it to an area large enough to change the atmosphere. As a result, the Sahara and Sahel (southern semi-arid regions of the Sahara), which favor vegetation, receive increased rainfall. This will then increase the rainfall (because the plants take a lot of water from the ground and “sweat” through their leaves), which will bring in more plants, which will absorb more of the energy from. Earth, sun, etc. These effects are described as “beneficial” in the study, which is easy to understand, but at least in some cases, it shows that really huge solar power plants can wreak havoc on the climate.

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A Another study on the same subject Part of it is the conclusion that a solar power plant, which makes up 20% of the Sahara, will literally have planetary effects (drought in the Amazon, warming in the Arctic, etc.). This is now a simple modeling, so we will have to see if others will reach comparable results – and then, if these predictions are made a reality – but yes, in principle it is possible to say that solar power plants, if they are magnificent and built in a particular context, have a global impact on the climate. It does not need to be heated as Mr. Le May requested, but it can theoretically “disturb”.

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