Researchers at Stanford University found a new way to make solar power production more than twice as efficient compared to conventional methods.
According to the researchers, the new process excels at higher temperatures, compared to existing photovoltaic technology which becomes less efficient for that case. The process is dubbed ‘PETE’ (photon enhanced thermionic emission).
“This is really a conceptual breakthrough, a new energy conversion process, not just a new material or a slightly different tweak.It is actually something fundamentally different about how you can harvest energy,” said Nick Melosh, an assistant professor of materials science and engineering, who led the research group.
Generally speaking, photovoltaic cells such as those used in rooftop solar panels convert the energy from photons to electricity by using a semiconducting material – silicon. The cells are capable to use a little portion of the light spectrum, with the rest just absorbing heat. This heat from unused sunlight and inefficiencies in the cells themselves account for a loss of more than 50 percent of the initial solar energy that reaches the cell.
The idea is to harvest this wasted heat energy so the solar cells could become much more efficient. To power heat-based conversion systems high temperatures are needed, but at higher temperatures, the solar cell’s efficiency rapidly decreases. Until today, nobody had come up with a method to combine photovoltaic and thermal conversion technologies.
The team of researchers have figured out how to made a semiconducting material able to use both heat and light to produce electricity. This thing is possible by coating a piece of that material with a thin layer of cesium – a metal.
“What we’ve demonstrated is a new physical process that is not based on standard photovoltaic mechanisms, but can give you a photovoltaic-like response at very high temperatures. In fact, it works better at higher temperatures. The higher the better.” Melosh said.
The high temperatures at which PETE performs (over 200 degrees C) are perfect for producing usable high temperature waste heat. The team also said that if PETE would be combined with a thermal conversion cycle, it could make solar cells reach even a 60% efficiency .