Electrifying heat is easy until the process needs a thousand degrees.

Industrial heat is roughly a fifth of global energy use and it does not decarbonise as a single problem. It decarbonises as three problems separated by temperature.

Below about one hundred and fifty degrees, industrial heat pumps work now, at reasonable cost, with payback periods that finance departments recognise. Food processing, paper drying and much of chemicals sit here.

The middle band

Between roughly one hundred and fifty and five hundred degrees, electric boilers, resistance heating and thermal storage are technically available but the economics depend almost entirely on the local electricity price relative to gas. In markets with cheap renewable power and high carbon prices it already pencils. Elsewhere it does not.

The hard end

Above eight hundred degrees, and particularly in processes where the fuel is also a chemical input, substitution is not a matter of swapping the heat source. Cement clinker and primary steel are the canonical cases, and both require process redesign rather than fuel switching.

Thermal storage is the quiet winner

Heating a refractory brick mass with cheap surplus electricity and discharging it as process heat is unglamorous engineering with no scientific uncertainty. Several European and American installations now run commercially, and the economics improve every time negative price hours increase.

How to read announcements

Ask the temperature. An announcement that does not state the process temperature is usually describing the easy band and implying the hard one.