Fourth Power Raises $20M for Low-Cost Thermal Energy Storage

US startup Fourth Power secured $20 million in Series A Plus funding to advance its thermal energy storage system. The company plans to deploy a 1 megawatt-hour demonstration unit by September 2025. This system uses molten tin to store heat, offering energy storage at a fraction of lithium-ion battery costs. Fourth Power aims to provide grid-scale storage lasting over 100 hours. This capability addresses renewable energy intermittency, supporting wind and solar power integration. The modular design allows utilities to scale storage capacity efficiently. Funding will also establish supplier and customer partnerships. Fourth Power's approach seeks to improve renewable energy affordability and grid reliability. The company anticipates this technology will accelerate the transition from fossil fuels.