Physicists at the Harvard School of Engineering and Applied Sciences (SEAS) have conceptualized a device that could produce energy from the Earth’s natural infrared radiation emissions into outer space.
The Earth continuously emits 100 million gigawatts of infrared heat into outer space, enough to provide for all of humanity’s power needs many thousands of times over. If technology could capture even a fraction of that, mankind’s energy problems would end. Heated by the sun, earth is warm compared to the frigid vacuum of space. Because of recent technological advances SEAS researchers say that this heat imbalance could soon be transformed into direct-current (DC) power, taking advantage of a vast and untapped energy source.
Harvard University researchers have developed two designs for their “emissive energy harvester” device that would convert IR radiation into usable power.
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One device would resemble a photovoltaic solar panel, but instead of capturing incoming visible light, it would generate electric power by releasing infrared light. The mechanism would consist of a “hot” plate at the ambient temperature of the earth and air below a “cold” plate, facing upward, made of a highly emissive material that cools by very efficiently radiating heat to the sky. Based on measurements of infrared emissions in Lamont, Oklahoma (as a case study), SEAS researchers calculate that the heat difference between the plates could generate a few watts per square meter, day and night. Keeping the “cold” plate cooler than the ambient temperature would be difficult, but the design illustrates the general principle that temperature differences can be used to generate electricity. The second proposed device relies on temperature differences between nanoscale diodes and antennas rather than a temperature that you could feel with your hand.
Federico Capasso, Harvard SEAS principal investigator, Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering describes the concept as “the use of physics at the nanoscale for a completely new application. We’re talking about the use of physics at the nanoscale for a completely new application. The mid-IR has been, by and large, a neglected part of the spectrum. Even for spectroscopy, until the quantum cascade laser came about, the mid-IR was considered a very difficult area to work with. People simply had blinders on.”
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Professor Capasso has a world-class reputation as an expert in semiconductor physics, photonics, and solid-state electronics. Not resting on academic publishing laurels in the ivory tower, Professor Capasso two decades ago co-invented the infrared quantum-cascade laser, has been a pioneer in the field of bandgap engineering and scientifically demonstrated through experimentation an elusive quantum electrodynamical phenomenon labeled the repulsive Casimir force—work for which he has received the SPIE Gold Medal, the European Physical Society Prize for Quantum Electronics and Optics, and the Jan Czochralski Award for lifetime achievement.
Professor Capasso acknowledged the gap between theory and practicality, observing, “It’s not at all obvious, at first, how you would generate DC power by emitting infrared light in free space toward the cold. To generate power by emitting, not by absorbing light, that’s weird. It makes sense physically once you think about it, but it’s highly counterintuitive.”
Those with a technological bent can read the SEAS research results in Steven J. Byrnes, Romain Blanchard, and Federico Capasso, "Harvesting renewable energy from Earth’s mid-infrared emissions."
By John Daly of Oilprice.com