Impact of power supply fluctuation and part load operation on the efficiency of alkaline water electrolysis

This is the research data folder for the paper "Impact of power supply fluctuation and part load operation on the efficiency of alkaline electrolysis". The current-voltage model data was obtained by conducting chronopotentiometry experiments on a lab-scale electrolyser. Available performance data were analysed and used for the commercial electrolysers. The large-signal dynamic model input variables were obtained by conducting Electrochemical Impedance Spectroscopy Experiments (EIS) on a lab-scale electrolyser. While commercial systems performance data were translated into electrochemical fundamentals on electrokinetics and ohmic resistance. Abstract: Contrary to traditional electrolysers which operate continuously at their nominal load, future alkaline electrolysers need to be able to operate over a wide load range due to the variability of renewable electricity supply. We have investigated how the residual ripples from thyristor-based power supplies are influenced by the operating load of the system, and how these ripples affect the efficiency of alkaline electrolysers. For this, a simulation tool was developed which combines a six-pulse bridge thyristor rectifier model with closed-loop current control and semi-empirical electrolysis models. The electrolysis models can simulate the potential response to both direct and high amplitude alternating currents for lab-scale and industrial electrolysers. The electrolysis model of the lab-scale electrolyser was validated with experiments with a square wave current input. The models show that without filters the ripples result in a total system efficiency loss of 1.2 – 2.5% at full load and of 5.6 – 10.6% at a part load of 20% depending on the type of electrolyser. The implementation of an optimized L-filter suppresses residual ripples and reduces the efficiency losses to 0.5% - 0.8% at full load and to 0.8 – 1.2% at the minimum load.