Techno-economic evaluation of waste heat recovery from an off-grid alkaline water electrolyzer plant and its application in a district heating network in Finland

The expected extensive production of hydrogen through water electrolysis will generate a substantial quantity of industrial waste heat. Waste heat recovery from electrolyzer facilities would provide significant potential for renewable heat generation into district heating (DH) networks. This paper investigates the techno-economic potential for recovering waste heat from an off-grid alkaline water electrolyzer (AWE) plant and using the heat in a DH network under Nordic conditions. A waste heat recovery system that includes heat pumps, a pit thermal energy storage (PTES) and an electric boiler is modeled and component capacities are cost-optimized for four different scenarios with varying DH demand coverage rates. The waste heat generation of the AWE plant and the DH demand are based on measurements conducted in southeastern Finland. It was found that even with 100 % DH demand coverage rate, the levelized cost of heat (LCOH) would be 44 €/MWh. Heat pumps constitute the largest single cost while the share of the PTES in the LCOH varies between 11 % and 19 %. The results were compared with the estimated renewable hydrogen production capacity of Finland, leading to the conclusion that by 2040, there could be potential to fulfill the DH demand of the entire country.