Earth's Own 'Body Heat' Could Be The Next Renewable Resource
There are several fairly obvious renewable energy types: wind, hydro, solar, geothermal, biofuel, biomass. But there's one that, until now, no one had formally considered. Scientists at Harvard University have recently proposed harnessing the Earth's own heat and infrared energy similar to the way we collect the sun's, with one key difference. Instead of converting incoming heat to electricity, they want to convert it on the way out.
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In a paper published Monday in Proceedings of the National Academy of Sciences, the researchers describe methods for turning the Earth's warmth into usable power. It wouldn't be like geothermal power, which exploits the magma locked beneath the crust; rather, it's more like the Earth's body heat. The sun is constantly warming the Earth through convection, conduction, and radiation. The Earth, in turn, transfers that energy back into the cold vacuum of space by the same means.
"It is possible to harvest energy from Earth's thermal infrared emission into outer space," the authors write. "We calculate the thermodynamic limit for the amount of power available, and as a case study, we plot how this limit varies daily and seasonally in a location in Oklahoma." Lamont, to be precise. They suggest two means of taking advantage of the Earth's heat emissions: one is a heat engine, which captures the energy of the Earth's heat as it transfers to a cold surface. The other is more like photovoltaics, the technology behind solar panels. This relies on temperature differences between nanoscale electronic components to generate an electrical current.
According to their calculations, a heat engine put to work using the Earth's natural thermal energy could generate "a few watts per square meter," Harvard reported Monday. "The device could be coupled with a solar cell, for example, to get extra power at night, without extra installation cost," said lead author Steven J. Byrnes.
As for the latter method, which they call an "optoelectronic emissive energy harvester," the amount of energy it generates depends on the quality of the technology. The researchers say engineers have made vast improvements in the kinds of materials needed to make the idea work, including the ability to scale devices for commercial production. "Now that we understand the constraints and specifications we are in a good position to work on engineering a solution," Byrnes says.
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