Embracing the Dark Side: The Science Behind Solar Panels Drawing Energy at Night
It’s common knowledge how solar panels work in the day. An average person on the street will be able to tell you they harvest light from the sun which is then converted into power. Solar enthusiasts will be able to speak more expansively, detailing how photovoltaic cells absorb the sun’s energy, convert it to DC electricity, and then see the solar inverter convert DC electricity to AC electricity for use throughout a home or business. Yet regardless of the general knowledge that exists surrounding solar panel use during the day, their use at night remains a novel—if not totally foreign—idea to most.
But there is progress being made in this area. With real optimism surrounding how solar panels in the future could continue to generate a significant amount of energy during the night in locales with normal-to-high levels of annual daily sunshine hours, and become more effective in the darker winter months. This has widespread implications for solar installations of all kinds, especially for the possibility of a hybrid system being developed that could utilize the current (hereafter called “conventional” solar panels) and this new form of a “night solar panel” (NSPs AKA “anti-solar panels”).
So what’s the science behind solar panels operating at night? And how may they be used alongside conventional solar panels?
HOW NSPs could work
The science behind NSPs is based upon research put forward by Tristan Deppe and Jeremy N. Munday, academics from the University of California Davis.
In their paper Nighttime Photovoltaic Cells: Electrical Power Generation by Optically Coupling with Deep Space, Deppe and Munday point out the current drawback with existing solar technology, namely that it only harvests energy during daylight hours. In turn, that via the use of a concept where the night sky is used as a heat sink and the earth as a heat source, a photovoltaic cell that generates energy at night could be effective. Put simply, while conventional solar panels are cold and the sun is hot, NSPs would essentially invert that concept by emitting radiation via infrared that would then create electron-hole pairs in space thanks to the latter’s cool temperatures.
Although NSPs represent a different operation from how conventional solar panels work, there are still shared elements between the two types. As Professor Munday explained:
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.