Firebrick systems powered by renewable energy could be used for up to 90% of industrial process heat applications, the Stanford study says. Meeting that demand in the U.S. would require firebrick system capacity of 2.6 TWh, with a peak discharge rate of 170 GW.
They use hot air warmed by gas burners.
Since we’re using electricity here, and this was mentioned in the study linked elsewhere, they used ceramic heaters.