Glass furnaces operate somewhere around 1500 C. Electrical heating would work, but that's also quite expensive, usually even more so.
What they'd want to do is try to recover and reuse heat. In principle, there's no reason "new" heat has to be added each time they heat a batch of glass, if heat can be transferred from cooling glass back to the input materials.
What they'd want to do is try to recover and reuse heat. In principle, there's no reason "new" heat has to be added each time they heat a batch of glass, if heat can be transferred from cooling glass back to the input materials.