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Humanity makes most of its electricity from heat that boils water to make steam to drive turbines.
However, the typical turbine uses only about 35 percent of that heat energy; the rest is wasted. Also, turbines’ moving parts degrade at temperatures above about 3,600°F, or about 2,000°C.
MIT has overcome both limitations by making an engine that turns heat into electricity with no moving parts, reaching about 40 percent efficiency, and operating in temperatures as high as 4,300°F or 2,400°C.
The new device doubles the efficiency of past so-called “thermophotovoltaic” devices, also known as heat engines.
Heat engines work by absorbing heat on one side and ejecting photons—waves or particles of light—from the other.
The photons are collected by an ordinary photovoltaic panel and converted to electricity.
MIT’s new version uses materials that absorb more heat and release higher-energy infrared photons.
Also, the collecting photovoltaic panel is layered, with the top layer collecting the infrared photons and a layer underneath snagging lower-energy light.
The breakthrough suggests designs for cheaper, simpler power plants.
MIT’s engineers also see it as a way to build better grid-scale storage batteries: excess electricity could heat insulated banks of graphite that would store energy until needed, when MIT’s heat engine would convert it back to electricity.
At 50-percent efficiency, the design would lag lithium batteries’ 70 percent, but would cost only about a tenth as much, the developers said.
The proof-of-concept device is less than a half-inch square but poses no obvious difficulties to scaling it for commercial use, the researchers noted.
TRENDPOST: MIT’s heat engine is safer as well as more environmentally friendly than conventional steam turbine technology or today’s thermophotovoltaic engines.
Just as important, it’s cheaper than either and requires less lithium.
As a result, the new heat engine could be shaking up the electric generation and storage industries before the end of this decade.