Anti-Solar: Turning solar energy inside out

The boom in solar power provision has opened doors for new-thinking around heat-based energy which could potentially allow for 24hour energy production, presenting a fascinating opportunity to balance the power grid over a full day-to-night cycle.

Innovative scientists have proposed plans to develop Anti-Solar Panels: which generates energy in the dark by capturing heat leaving the Earth’s surface at night and converting it into useable power. Intriguingly, Anti-Solar could also work during the day, by positioning panels facing away from the Sun or if active steps are taken to block direct sunlight.

Professor Jeremy Munday, an electrical and computing engineer at University of California (Davis), detailed proposals for the development of “night-time photovoltaic cells” also termed “Anti-Solar”, which could generate power at night.

In a statement on the UC Davis website Prof. Munday explained that thermo-radiative cells, when pointed at the night sky, emit infrared light because Earth is warmer than outer space;

“We were thinking, what if we took one of these devices and put it in a warm area and pointed it at the sky?”

This new system to harness energy in darkness is based on the concept of using heat to generate energy but through the inverse of the solar panel methodology.

Detailing his plans, Prof. Munday proposed that the ‘night-time’ panel would work using a thermo-radiative cell to emit infra-red radiation from the Earth into space to create electron-hole pairs. In simple terms, while regular solar panels capture heat energy generated from the Sun, the Anti-Solar panel aims to trap heat radiated from Earth’s surface overnight and convert it to usable energy.

“A regular solar cell generates power by absorbing sunlight, which causes a voltage to appear across the device and for current to flow.” He said. “In these new devices, light is instead emitted, and the current and voltage go in the opposite direction, but you still generate power. You have to use different materials, but the physics is the same”

Traditional solar panels rely on direct sunlight, their capacity limited at night and when sunlight becomes obscured.

Speaking to CNN, Munday said “Solar cells are limited in that they can only work during the day, whereas these devices can work 24/7, which is the real advantage. Nobody wants to lose power once the sun sets.”

At this point, the prototype device does not have the energy harvesting capabilities of the traditional solar panel - only producing 50watts of electricity per m2 under ideal conditions - around one quarter of the daily output generated by traditional solar panels.

Improvements for the device are already in place, as researchers plan to enhance the insulation abilities that could increase the device’s energy production capability further. Current research suggests that if the panels are developed, an additional benefit is their ability to keep generating power without the need to store excess electricity in batteries.

And that’s not all. According to Prof. Munday, there is also potential for another device which can be adapted to run on excess heat produced from industrial processes, a potential boon for a transitioning industry. These thermo-radiative cells, generate energy by radiating heat to its surroundings and scientists have been exploring how to use them to capture waste heat from engines.