Fourth Power’s sci-fi thermal batteries could be cheaper than pricey natural gas power plants

Fourth Power is developing thermal batteries to revolutionize renewable energy storage. The system heats carbon blocks, then pumps 2,400°C molten tin through graphite pipes, converting heat back to electricity. The Cambridge-based startup plans to deliver commercial batteries by 2028, potentially cheaper than lithium-ion batteries and natural gas plants. The system can provide power for eight hours or more with minimal energy loss. Fourth Power raised $20 million to build a demonstration battery, aiming to reduce storage costs to $25 per kilowatt-hour.