PV cells that generate power at night?

One of the biggest challenges of solar is balancing load using storage to deliver power when the sun isn't shining. But what if we could run PV cells in reverse and generate electricity at night? Turns out we can.

Jeremy Munday and graduate student Tristan Deppe from the Department of Electrical and Computer Engineering at UC Davis are proposing a PV cell that generates 50 Watts per square metre at night – around 25% what a conventional solar panel produces during the day.

From UC Davis

A conventional photovoltaic or solar cell (left) absorbs photons of light from the sun and generates an electrical current. A thermoradiative cell (right) generates electrical current as it radiates infrared light (heat) toward the extreme cold of deep space. UC Davis engineers propose that such cells could generate a significant amount of energy and help balance the power grid over the day-night cycle. (Tristan Deppe/Jeremy Munday)

Munday commented…

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

“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… You have to use different materials, but the physics is the same.”

The paper was published in ACS Photonics.

Nighttime Photovoltaic Cells: Electrical Power Generation by Optically Coupling with Deep Space

Abstract

Photovoltaics possess significant potential due to the abundance of solar power incident on earth; however, they can only generate electricity during daylight hours. In order to produce electrical power after the sun has set, we consider an alternative photovoltaic concept that uses the earth as a heat source and the night sky as a heat sink, resulting in a “nighttime photovoltaic cell” that employs thermoradiative photovoltaics and concepts from the advancing field of radiative cooling. In this Perspective, we discuss the principles of thermoradiative photovoltaics, the theoretical limits of applying this concept to coupling with deep space, the potential of advanced radiative cooling techniques to enhance their performance, and a discussion of the practical limits, scalability, and integrability of this nighttime photovoltaic concept.

 

Image credit: The authors & UC Davis.

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