Phot by Nick Melosh
We currently have two types of solar energy: energy generated from light, using silicon-based photovoltaic cells, and energy generated from heat, using solar concentrators and heat-conversion systems. What if we could collect both types of energy at once? Stanford researchers recently unveiled a new solar tech that can do exactly that — their PETE devices utilize a semiconducting material coated with cesium to boost efficiency levels up to 60 percent — three times that of existing systems.
Rooftop solar panels use silicon to convert light into electricity. But their efficiency declines rapidly at higher temperatures (like those needed to power heat-conversion systems). An either/or choice presents itself — but Stanford researchers found that a cesium coating allowed semiconducting materials to convert both light and heat into energy.
They dubbed the process PETE, for photon enhanced thermionic emission. Best of all, PETE devices could be cheaply and easily incorporated into existing solar collection systems. (Because the system hits peak efficiency at over 200 degrees Celsius, it’s not a good fit for rooftop arrays.) “The light would come in and hit our PETE device first,” explained lead researcher Nick Melosh. “We would take advantage of both the incident light and the heat that it produces, and then we would dump the waste heat to existing thermal conversion systems.”
PETE devices require only a small amount of semiconducting material, making them cheap. Melosh’s team also hopes to design devices that can easily be bolted on to existing solar collection systems, so that conversion would also be low-cost.
When used with the heat-conversion process, PETE devices could reach 60 percent efficiency. But even if they boost efficiency just to 30 percent, they will bring solar power down to the price point of oil. And that’s a good thing.