Stable Thermal Regime in an Alkaline Water Electrolyser System

Experimental alkaline water electrolysis (AWE) systems require precise thermal management to achieve stable electrochemical efficiency. Manual operation of laboratory-scale electrolysers often induces thermal fluctuations that lead to excessive overpotentials. In this work, a real-time data acquisition (DAQ) and automated temperature-control architecture were implemented in a 3 kW nominal alkaline electrolyser in order to observe the thermal stability regime. The system was evaluated using a stepped-current protocol derived from FCTESTNET standards. Current densities of 0.3 and 0.5 A·cm−2 were investigated, corresponding to operating currents of approximately 22.5 A and 40 A, respectively. Variations in manually controlled conditions raised temperature values to near 100 °C. With the implemented control system, two distinct thermal regimes were observed. At 0.3 A·cm−2, cyclic behaviour between 60 and 80 °C was recorded due to on–off cooling dynamics. At 0.5 A·cm−2, the system reached a stable thermal regime between 70 and 75 °C, maintaining steady-state fluctuations within ±1 °C after transient stabilisation. It was observed that the electronically controlled thermal system reduced temperature-induced overpotentials and improved voltage stability during long-duration tests. The results demonstrate that integrating automated thermal control enhances operational safety and enables reproducible electrolyser evaluation under controlled laboratory conditions.