Temperature optimization of PEM water electrolyzers for minimum hydrogen prices

Increasing the temperature of PEM electrolyzers improves their efficiency but reduces their lifetime. This suggests the existence of an ideal temperature - characterized by a minimum hydrogen price - at which the electrolyzer is sufficiently efficient and long lived. Here, we evaluate the ideal temperature of a PEM electrolyzer as a function of material (membrane thickness, exchange current density), operational (current density, voltage degradation) and economic parameters (CAPEX, OPEX and electricity price). Increases in efficiency with temperature are calculated from a cell model. The lifetime decrease is taken from literature data and is supported by a model of PEM degradation. The ideal operating temperature decreases from 80 °C at 0.15 €/kWh (and higher) to 40 °C at 0.01 €/kWh. The relative influence of material, operational and economic parameters on the levelized cost of hydrogen is quantified, allowing for clear recommendations on a path to cost competitive hydrogen.