As reported in Nature, researchers at MIT have developed a heat engine, with no moving parts, that is as efficient (40%) as a steam turbine in converting high heat into electricity. Their heat engine is actually a thermophotovoltaic (TPV) cell—not unlike a solar panel’s photovoltaic cell—that “passively” converts photons from a high-temp source into electricity.
The MIT team's heat engine can generate electricity from heat sources between 1,900 to 2,400°C, or as high as 4,300°F.
According to the study, TPVs convert mostly infrared wavelength light to electricity via the “photovoltaic effect,” enabling energy storage [1, 2] and conversion [3, 4, 5, 6, 7, 8, 9] that uses “higher temperature heat sources than the turbines that are ubiquitous in electricity production today.”
The team’s cells use “band-edge spectral filtering” to achieve their engine’s higher efficiency, using back-surface reflectors to reject unusable radiation back to the heat emitter.
The study’s authors hope that cells such as theirs can be “integrated into a TPV system for thermal energy grid storage to enable dispatchable renewable energy,” creating a way for thermal energy grid storage to reach efficiency and cost levels that will enable decarbonization of the electricity grid.
As a result of their achievement, the researchers imagine that a “proliferation of (Thermophotovoltaic Electricity Grid System) TEGS could ultimately enable abatement of approximately 40% of global CO2 emissions,” by way of decarbonizing the electricity grid and enabling CO2-free electric vehicle charges. They believe that a TPV efficiency of 40% means that TEGS are now feasible, as are other applications in “natural gas, propane or hydrogen-fueled power generation [3, 4, 5, 6, 7, 8, 9], and high-temperature industrial waste heat recovery.”