Curved anthracene derivatives, organic molecules found in coal tar, store sunlight as chemical energy and release heat on demand

https://phys.org/news/2025-07-molecules-sunlight-chemical-energy-demand.html

"molecular solar thermal (MOST): structurally change upon absorbing sunlight, release heat when triggered to return to original shape... Dewar isomerization: energy storage in chemical bonds... energy locked in for long periods, released using heat, specific wavelength light, or catalyst... absorb not only UV but visible light, solvent-free, >28 cycles with minimal fatigue... formation of isomers crucial... up to 170 kJ/mol, 0.65 MJ/kg energy storage densities... recharge within 6–8 hours... fully carbon-based systems"

Related: EarthEn Heat Battery stores electricity and releases it as high-temperature steam or hot air (200°C to 500°C) on demand, with customizable 4-12 hour storage durations, up to 90% round-trip efficiency
https://www.altenergymag.com/news/2025/08/01/earthen-energy-launches-breakthrough-heat-battery-at-re-storage-to-decarbonize-industrial-heat-processes/45854