A recent breakthrough (pdf) by a team of researchers at the University of New South Wales (UNSW) could pave the way to a new form of energy generation that uses heat emitted from the Earth’s surface. Using a similar process to how solar cells convert sunlight into electricity, it could allow us to produce energy at night.
Solar panels use visible light produced by the sun: PV cells rely on silicon semiconductors that absorb the photons beamed down by the sun, and convert the thermal energy into electricity.
But this technology uses photons from a different source: The researchers used a device called a thermoradiative diode to instead capture energy produced by infrared light that is released by the Earth’s surface at night.
Solar energy minus the sun: This is still technically a form of solar energy. The infrared light is energy produced by the solar radiation that heats up the planet during the day. At night, these infrared photons are released, and can be captured using the device deployed by the UNSW scientists.
The technology is still in its infancy: The device was only able to generate 2.26 MW per square meter of electricity at 1.8% efficiency, which one of the study’s authors admits is “relatively very low power.” By comparison most commercial solar panels range between 15-20% efficiency. The team anticipates it could increase to some 19.4 MW per square meter or about “a tenth of the power of a solar cell,” under different conditions, one of the study’s co-authors said.
This isn’t the only option for night-time solar: Over on the other side of the Pacific, researchers at Stanford University have outfitted regular solar panels with thermoelectric generators to absorb infrared photons, says New Scientist. Though the amount of power the researchers have been able to generate has been small — 50 milliwatts per square meter or 0.04 percent of the output of an ordinary solar panel during the daytime — the technology could eventually be useful tools in powering small devices in remote regions.
This discovery could become a helpful supplement to solar power generation but not a substitute: There’s still a long way to go for this technology to be applied at scale and reach a point of higher efficiency but there are already some potential applications researchers have pointed to. Applying these same thermoelectric principles to biomedical devices could eliminate the need for batteries in artificial hearts by harnessing the power of body heat. Another example could include recharging or doing away with batteries on personal devices entirely.
But this is where private industry can really step in to help bolster uses for this technology: Similar to how the solar industry was supported by a huge boost in private investment, thermoradiative electricity could benefit from the same kind of attention. “ There's still about a decade of university research work to be done here. And then it needs industry to pick it up. If industry can see this is a valuable technology for them, then progress can be extremely fast,” Associate Professor and co-author of the study Ned Ekins-Daukes said.