Flexible endothermic or exothermic operation for temperature-oriented alkaline water electrolysis

Traditional 60°C–85°C alkaline water electrolysis (AWE) systems suffer from high specific energy consumption (4.4–5.3 kWh Nm −3 ), which is yielded by poor performance and consumes parasitic energy to remove excessive heat. This study presents construction of a 20 kW endo-/exothermic ET-AWE system, oriented by elevated temperature (ET), that achieves a performance of 1.768 V@0.612 A cm −2 for 5.314 Nm 3 h −1 hydrogen production while accomplishing ≥12 h thermoneutral operation. By trading off between system thermal and electrical energy requirements, a universal criterion to determine thermoneutral points yielding an optimal efficiency of 82.56%, and a decreased specific energy consumption of 4.293 kWh Nm −3 at 0.594 A cm −2 and 130°C is proposed. The capacity of ET-AWE systems to receive external heat from diversified thermal sources in endothermic mode is possible in this system. Flexible combined hydrogen and high-value heat supplies in exothermic mode allow for unique electric-hydrogen-heat coordination.