Two technologies, different heat signatures
Alkaline electrolyzers typically operate around 60 to 80 degC with large stack volume and steady low-grade rejection, plus a significant drying-room load. PEM electrolyzers run at higher current density and 70 to 90 degC, packing more heat into a smaller footprint with a higher heat-flux density.
What recovery must handle
Both technologies vent warm air from drying and compressor rooms and reject stack cooling heat. The right recovery device must isolate the streams (trace hydrogen or alkaline mist) and tolerate the relevant temperature. As outlined in emerging high-temperature core materials, material choice decides service life.
Matching the core
Use corrosion-resistant plate cores for ventilation and drying air. Where the loop is hotter or more aggressive, an all-welded plate extends the duty range beyond gasketed designs.
Bottom line
Regardless of PEM or alkaline, the recovery strategy is the same: capture steady low-grade heat with isolated sensible cores and route it to feed pre-heat and building heating.