Solar water heaters. And district heating that uses waste heat. (E.g. waste heat from data centers or industrial processes). Besides that you could run smeltin

Solar water heaters. And district heating that uses waste heat. (E.g. waste heat from data centers or industrial processes). Besides that you could run smelting ovens, internal combustion engines, and other furnaces of hydrogen. Though that hydrogen will probably come from electricity if it isn't polluting.