Solar and wind are cheap but variable, and lithium-ion batteries only cover short gaps. To handle multiday lulls, utilities need longer-duration storage. Three startups are pursuing very different chemistries and business models to fill that gap.
Form Energy uses iron-air batteries that store energy for 100 hours via a reversible rusting process, targeting $20 per kilowatt-hour to compete with natural gas. Energy Dome compresses carbon dioxide into liquid, storing it for up to 24 hours, and claims its systems are 10-15% cheaper than lithium-ion for eight-hour storage, though roundtrip efficiency is about 70%. Moment Energy repurposes used EV batteries, giving them a second life of 10-30 years, and says its systems cost under $90 per kilowatt-hour, though new batteries from China can be cheaper.
All three have signed commercial deals—Form with Minnesota utilities and Google, Energy Dome with Google in Ireland, and Moment with hospitals and airports. They also share a common challenge: scaling up. Form's production capacity is a fraction of its commitments, Energy Dome has only one operational plant, and Moment has deployed just 11 systems. Their success will depend on cost, reliability, and the ability to secure supply chains.
If these technologies mature, they could help renewables meet the surging electricity demand from data centers and reduce the need for natural gas peaker plants. But each faces trade-offs in efficiency, footprint, and economics, so the long-duration storage market remains wide open.