Solar thermophotovoltaic (STPV) cells are a technology for generating electricity from sunlight. A typical solar panel is made using photovoltaic cells, which generate energy directly from the photons in sunlight. STPV heat engines, in contrast, focus the full spectrum of sunlight onto an absorber. That heats up, and transfers thermal energy to an emitter. The emitter, in turn, outputs a photons in a much narrower light spectrum. That spectrum is optimized for the TPV cell to generate electricity more efficiently. But that efficiency has still been stalled at 23 percent for many years. Now, researchers from UC Berkeley may be able to push that up to a whopping 50 percent efficiency.
This breakthrough builds on a previous development the researchers published back in 2011. By adding a highly-reflective mirror behind the TPV cell, they were able to create a “dense infrared luminescent photon gas within the solar cell.” That added to the voltage being generated by the TPV cell. It also reflects some of the photons that were missed — because they had too little energy to generate electricity — back at the TPV cell. That further increases the efficiency up to 29 percent. By improving how reflective that mirror is, the team believes they can reach a groundbreaking 36 percent efficiency.
The hope is to combine this technique with others that have already been proven in order to get to an amazing 50 percent efficiency. That would, of course, be far more sustainable than generating electricity from fossil fuels. But it also provides additional opportunities. These STPV cells would be very light and require little maintenance, which makes them ideal for unmanned aerial vehicles and spacecraft. A drone equipped with an STPV generator that can achieve 50 percent efficiency could, theoretically, fly for days at a time. The technology could also be used to power homes, replacing traditional power plants.