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Heat AND Light: A Solar Update
Careful listeners to last week's show about solar energy might remember a call we got from Paul in Corvallis. He said that we shouldn't just focus on PV, or photovoltaic systems, to create electricity. He wanted to hear more about solar thermal systems, which basically use solar energy to heat water.
When our guests responded, it became clear that our existing technologies primarily capture solar energy in the form of either heat or electricity — but not both. But some some recent news from Stanford researchers seems to have bridged that gap. As the press release explains:
Most photovoltaic cells, such as those used in rooftop solar panels, use the semiconducting material silicon to convert the energy from photons of light to electricity. But the cells can only use a portion of the light spectrum, with the rest just generating 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 reaching the cell.
If this wasted heat energy could somehow be harvested, solar cells could be much more efficient. The problem has been that high temperatures are necessary to power heat-based conversion systems, yet solar cell efficiency rapidly decreases at higher temperatures.
Until now, no one had come up with a way to wed thermal and solar cell conversion technologies.
Now that they have done just that, the researchers say, solar energy could become efficient enough to compete with oil. Here's the full paper, which was published online on August 1st in Nature Materials. There's no mention in the press release of how long it might be before a commercial application is ready.