Thermophotovoltaic cells top 40 per cent efficiency

https://physicsworld.com/a/thermophotovoltaic-cells-top-40-percent-efficiency/

"maximum efficiency 41.1% and power density of 2.39 W/cm2 using heat source emitting at 2400 °C... first of two cell designs uses top and bottom junctions made from AlGaInAs and GaInAs grown on GaAs substrate...  second design combines lattice-matched 1.4 eV GaAs top cell with lattice-mismatched 1.2 eV GaInAs bottom cell... almost constant ‘penalty’ on voltage, moving to higher bandgaps (of 1.0 to 1.4 eV) confers advantage"

Related:

Scientists New Thermophotovoltaic Battery Breakthrough FINALLY Hit The Market

https://www.greentech-news.org/scientists-new-thermophotovoltaic-battery-breakthrough-finally-hit-the-market/

Malta Inc. Announces Key Milestone for Pumped-Heat Energy Storage System Deployment

https://www.valdostadailytimes.com/news/business/malta-inc-announces-key-milestone-for-pumped-heat-energy-storage-system-deployment/article_fa1b52b0-3b2b-5b71-88ef-bda8400e6906.htm

See also: Institute demonstrates first-of-its-kind small-scale pumped heat energy storage system

https://techxplore.com/news/2022-08-first-of-its-kind-small-scale-energy-storage.html