This article systematically compares six major solar energy storage methods, lithium-ion batteries, redox flow batteries, compressed air energy storage, thermal energy storage, hydrogen energy storage, and pumped-hydro energy storage, to determine which is most. This article systematically compares six major solar energy storage methods, lithium-ion batteries, redox flow batteries, compressed air energy storage, thermal energy storage, hydrogen energy storage, and pumped-hydro energy storage, to determine which is most. Energy storage facilities are becoming an increasingly popular solution among owners of photovoltaic installations. They allow the storage of surplus electricity, which contributes to greater energy independence and efficiency of the entire system. Storage systems turn solar power from a “use it or lose it” resource into a reliable, flexible energy source. Atlas Copco's guide on solar energy storage lays out the basics of thermal, mechanical, and. The AES Lawai Solar Project in Kauai, Hawaii has a 100 megawatt-hour battery energy storage system paired with a solar photovoltaic system. Sometimes two is better than one. Thermal storage involves capturing and storing the sun's heat, while battery storage involves storing power generated by solar panels in batteries for later use.