Sunrise, sunset: possibilities for night-time solar power

Harvesting power from the Sun in the dark? It's possible, says new research from UNSW Sydney.

During the day, electromagnetic radiation emitted by the Sun lights and warms our planet. At night, the sunlight absorbed by the Earth is re-radiated as infrared radiation as heat flows from the planet's surface into outer space. 

Whilst it has been predicted in the past that this re-radiated heat could be harnessed to generate power, it has not been straightforward to do this in practice. The innovative approach taken by the UNSW Sydney researchers uses a thermoradiative diode based on mercury cadmium telluride - a key compound in night vision technologies - to convert infrared radiation into electric current. 

At this stage, the levels of power generated by the thermoradiative diode are small - solar panels can supply around 100,000 times more - but the team say this is the first step towards making night-time solar power practical. (After all, the first silicon solar cell had an efficiency of less than 1%, and in April 2020, solar power generation broke records to supply almost 30% of the UK's electricity demand.) Let's hope this new technology has an equally sunny future awaiting it.