Night photovoltaic panels

Audio 02:07

By: Dominique Desaunay Follow

"Solar" panels may soon lose part of their name. The new prototypes of "thermoradiative" cells tested by researchers in the United States would allow the development of "photovoltaic" devices capable of delivering electricity day and night.

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Solar energy is not worth a tripod when the diurnal star illuminates the opposite face of our good old Earth which in addition does not stop rotating on itself roughly in 24 hours. And when it's dark, it's dark! There is no hope ! As Johnny Hallyday interpreted it in one of his songs.

An unavoidable truth for any night owl person not connected to an electrical network who would like their photovoltaic panels to deliver a little current to them in order to get out of the dark.

Besides, during the day and when it rains, it is not better! Most of our solar panels lose up to 90% of their efficiency in overcast weather. Whose fault is it? Technology, of course! But an American researcher from the Department of Electrical and Computer Engineering at the University of California-Davis may have a start to the solution. Its prototype photovoltaic cell is capable of generating around 50 Watts of electricity per square meter at night.

The process he employs is based on a physical phenomenon known for ages in thermodynamics: any hot body diffuses electromagnetic waves towards the colder areas of its environment.

This is exactly what is at work in conventional solar panels: the very hot star of the day, transfers a very small part of its energy to the much colder photovoltaic collectors, creating in the process a tension in the material which makes up the cells of the device to generate electricity. The prototype of the researcher who seems to do the opposite, however, respects the same laws that physics imposes on us. "Rather than being cold and pointed at the hot Sun, the cells of these devices are hot and pointed at something colder", like the deep space which is really freezing, explains the scientist in the journal ACS Photonics .

For now, his device works only in optimal conditions, that is to say with a cloudless night sky and dry weather. It generates about a quarter of what a conventional solar panel can produce in a day. But the technologies of “thermoradiative” cells which have been known for a long time offer us a definite advantage over systems, that of being able to operate day and night. Sunscreen panels which would undoubtedly allow us to approach the energy transition more serenely, without fear of alternative power cuts.

You have questions or suggestions, you can write to us at nouvelles.technologies@rfi.fr

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