Anti-Sol­ar Cells: A Photo­vol­ta­ic Cell That Works at Night

Munday, who recently joined UC Dav­is from the Uni­ver­sity of Mary­land, is devel­op­ing pro­to­types of these night­time sol­ar cells that can gen­er­ate small amounts of power. The research­ers hope to improve the power out­put and effi­ciency of the devices. Munday said that the pro­cess is sim­il­ar to the way a nor­mal sol­ar cell works, but in reverse. An object that is hot com­pared to its sur­round­ings will radi­ate heat as infrared light. A con­ven­tion­al sol­ar cell is cool com­pared to the sun, so it absorbs light. Space is really, really cold, so if you have a warm object and point it at the sky, it will radi­ate heat toward it. People have been using this phe­nomen­on for night­time cool­ing for hun­dreds of years. In the last five years, Munday said, there has been a lot of interest in devices that can do this dur­ing the day­time (by fil­ter­ing out sun­light or point­ing away from the sun).

Gen­er­at­ing power by radi­at­ing heat

There’s anoth­er kind of device called a ther­mora­di­at­ive cell that gen­er­ates power by radi­at­ing heat to its sur­round­ings. Research­ers have explored using them to cap­ture waste heat from engines. ​“We were think­ing, what if we took one of these devices and put it in a warm area and poin­ted it at the sky,” Munday said. This ther­mora­di­at­ive cell poin­ted at the night sky would emit infrared light because it is warm­er than out­er space. ​“A reg­u­lar sol­ar cell gen­er­ates power by absorb­ing sun­light, which causes a voltage to appear across the device and for cur­rent to flow. In these new devices, light is instead emit­ted and the cur­rent and voltage go in the oppos­ite dir­ec­tion, but you still gen­er­ate power,” Munday said. ​“You have to use dif­fer­ent mater­i­als, but the phys­ics is the same.” The device would work dur­ing the day as well, if you took steps to either block dir­ect sun­light or poin­ted it away from the sun. Because this new type of sol­ar cell could poten­tially oper­ate around the clock, it is an intriguing option to bal­ance the power grid over the day-night cycle. Source: UC Dav­is (Ori­gin­al writ­ten by Andy Fell), News, 29.01.2020