Static–dynamic modelling of the electrical behaviour of a commercial advanced alkaline water electrolyser

Abstract

This paper analyses the permanent and transient behaviour of a 1Nm3h−1 commercial advanced alkaline water electrolyser and develops a complete and integrated static–dynamic electrical model that can be applied to any commercial water electrolyser. The model is based on the thermodynamic, activation, double-layer and ohmic effects and phenomena that take place in a real alkaline electrolysis process. The parameters of the model are experimentally determined from both static and dynamic operating tests to the electrolyser. Based on these tests, the electrical behaviour of the electrolyser has been characterized, concluding that, at operating conditions of 45°C and 25bar, the cell area-specific resistance is 0.431Ωcm2 and the cell specific double-layer capacitances are 0.0467Fcm−2 for the anodic interface and 2.25×10−3Fcm−2 for the cathodic interface. The model has been implemented on MATLAB-Simulink® and validated in three different operating environments: at static operation by means of the I–V characteristic curves; at dynamic operation by means of a sinusoidal current of various amplitudes and frequencies superimposed to a DC current; and by using two power supplies with different conversion topologies, the first one harmonic free and the other with a high harmonic content. As it will be shown in the paper, the model simulations reproduce with a high accuracy the experimental electrical behaviour of the electrolyser.