It could be a REN-revolution.

What if solar cells worked at night?

According to Jeremy Munday, professor in the Department of Electrical and Computer Engineering at UC Davis,

a specially designed photovoltaic cell could generate up to 50 watts of power per square meter under ideal conditions at night.

It’s about a quarter of what a conventional solar panel can generate in daytime.

Munday is developing prototypes of these “night-solar” systems. The researchers hope to improve the power output and efficiency.

The principle:

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 cold, so if you have a warm object and point it at the sky, it will radiate heat toward it.  

More: https://www.ucdavis.edu/news/anti-solar-cells-photovoltaic-cell-works-night/