Heavy industries generate about a quarter of worldwide emissions, and alternative power sources can't consistently generate the amount of heat that factories need to create their wares. A growing number of companies are working on systems that can capture heat generated by clean electricity and store it for later in stacks of bricks. They think these bricks could be the key to bringing renewable energy to some of the world's biggest polluters. Many of these heat storage systems use simple designs and commercially available materials, meaning they could be built quickly, anywhere they're needed. Although it's in early stages, the technology could be one building block of a new, climate-friendly industrial sector.