https://news.ycombinator.com/item?id=33431427 https://news.ycombinator.com/item?id=33431427 : > FWIU, heat engines are useful with all thermal gradients: pipes

https://news.ycombinator.com/item?id=33431427 https://news.ycombinator.com/item?id=33431427 : > FWIU, heat engines are useful with all thermal gradients: pipes, engines, probably solar panels and attics; "MIT’s new heat engine beats a steam turbine in efficiency" (2022) https://www.freethink.com/environment/heat-engine https://www.freethink.com/environment/heat-engine "Thermophotovoltaic efficiency of 40%" (2022) https://www.nature.com/articles/s41586-022-04473-y https://www.nature.com/articles/s41586-022-04473-y https://scholar.google.com/scholar?cites=14197364440245631757&as_sdt=5,43&sciodt=0,43&hl=en https://scholar.google.com/scholar?cites=1419736444024563175... "Capturing Light From Heat at 40% Efficiency, NREL Makes Big Strides in Thermophotovoltaics" (2022) https://www.nrel.gov/news/program/2022/capturing-light-from-heat-at-40-percent-efficiency-nrel-makes-big-strides-in-thermophotovoltaics.html#:~:text=Careful%20Design%20Yields%20World%2DRecord,slightly%20different%20wavelengths%20of%20light https://www.nrel.gov/news/program/2022/capturing-light-from-.... : > The 41%-efficient TPV device is a tandem cell—a photovoltaic device built out of two light-absorbing layers stacked on top of each other and each optimized to absorb slightly different wavelengths of light. The team achieved this record efficiency through the usage of high-performance cells optimized to absorb higher-energy infrared light when compared to past TPV designs. This design builds on previous work from the NREL team. > Another crucial design feature leading to the high efficiency is a highly reflective gold mirror at the back of the cell. Much of the emitted infrared light has a longer (less energetic) wavelength than what the cell's active layers can absorb. This back surface reflector bounces 93% of that unabsorbed light back to the emitter, where it is reabsorbed and reemitted, improving the overall efficiency of the system. Further improvements to the reflectance of the back reflector could drive future TPV efficiencies close to or above 50%. Thermoelectric effect: https://en.wikipedia.org/wiki/Thermoelectric_effect https://en.wikipedia.org/wiki/Thermoelectric_effect Thermophotovoltaic energy conversion *: https://en.wikipedia.org/wiki/Thermophotovoltaic_energy_conversion https://en.wikipedia.org/wiki/Thermophotovoltaic_energy_conv... Thermophotonics: https://en.wikipedia.org/wiki/Thermophotonics https://en.wikipedia.org/wiki/Thermophotonics Gas turbine: https://en.wikipedia.org/wiki/Gas_turbine https://en.wikipedia.org/wiki/Gas_turbine : > gross thermal efficiency exceeds 60%. [100] (2011) GE-7HA https://www.ge.com/news/press-releases/ha-technology-now-available-industry-first-64-percent-efficiency https://www.ge.com/news/press-releases/ha-technology-now-ava... (2017) : > that its largest and most efficient gas turbine, the HA, is now available at more than 64 percent efficiency in combined cycle power plants, higher than any other competing technology today. How do TPV operating and lifecycle costs differ from gas turbine's costs?