Our electric future needs low-cost long-duration storage for grids. Per kWh, pumped hydropower is about $60, compressed air energy storage (CAES) costs from $150 to $300, and lithium-ion batteries cost around $300 (and only store energy from one to four hours). Wayne Hicks at NREL describes research into thermal energy storage (TES) using solid particles such as sand which is abundant worldwide. With a duration lasting hundreds of hours, … [Read more...]