Storing energy from renewable power sources such as solar and wind remains a challenge. The use of large battery packs is expensive; relies on nonrenewable, environmentally problematic minerals like lithium; and comes with inherent safety risks. California-based Antora Energy is investigating ways to store energy inside insulated boxes of extremely hot rocks. The technology is based on blast furnaces that use massive towers of stacked bricks to absorb wasted heat to provide energy.

Antora’s innovation uses solar electricity to heat blocks of carbon to almost 3,000° Fahrenheit, preserving it for later use. The stored thermal energy can then be delivered to customers as electricity or on-demand industrial-process heat. Antora’s use of hot carbon solves the unreliability of providing 24/7 zero-carbon power solely with solar and wind energies, which vary depending on the weather. Notably, the rocks are not heated by burning coal or gas but by capturing sunlight with thousands of photovoltaic solar panels.

Company leaders assert that this technology is compact and modular, making it flexible enough to be configured to fit different needs, and manufacturers will not have to wait for grid connections and upgrades. Whether this technology can be scaled to meet the growing demand remains to be seen.