A startup called Cache Energy is developing a cement-based battery that could dramatically reduce fossil fuel use for heating. The technology stores heat rather than electricity, using a simple chemical reaction between quicklime and water to create calcium hydroxide. This ancient Roman concrete formula forms the basis of a thermal battery that can be recharged and discharged repeatedly.

Heating accounts for a massive 30% of global energy consumption, with 20% used for industrial processes and 10% for homes and water. By storing heat from cheap renewable sources, this cement battery could displace much of the natural gas and other fossil fuels currently used for these applications. The chemistry is deliberately simple to ensure scalability and cost-competitiveness.

The potential market impact is significant. If successful, this technology could transform how industries and homes are heated, reducing dependence on fossil fuels while leveraging an ancient material in a novel way. The combination of proven chemistry and modern engineering could make renewable heating economically viable at scale.