Current switching device development to characterise and monitor a proton exchange membrane water electrolyser

Abstract

The development and of key hydrogen production techniques play an essential role in the evolution of renewable energy solutions. Numerous studies have been carried out in recent years to improve and enhance these techniques, including the proton exchange membrane water electrolysis (PEMWE) process, which has produced encouraging technological outcomes that will enable the efficient and sustainable generation of hydrogen. Furthermore, because of its high current density, higher energy efficiency compared to alkaline water electrolysis, high hydrogen discharge pressures, and smaller gas crossover, the PEMWE device is an ideal high purityhydrogen generation approach. In contrast to the alkaline water electrolysis technique, the PEMWE technology is still relatively new and has a number of intricate components and interfaces that call for particular characterisation techniques in order to get a deeper basic understanding. However, alternative cell characterisation techniques are still being investigated as to efficiently monitor and control the cell with minimal resources and response times.

The research presented in this dissertation focussed on the current interrupt (CI) method, entailing the development of a current switching (CS) approach to characterise a PEMWE cell. The CS method includes the design of a CS development board responsible for producing an attenuated and controlled perturbation signal generated via an STM32 microcontroller. This signal is responsible for the control of the cell supply current administered within a frequency range of 0.8 Hz – 20 kHz. Furthermore, the voltage and current signals measured through each experiment were recorded and analysed using Matlab® and Simulink®. However, to characterise the PEMWE cell, an equivalent electrical circuit (EEC) was designed to represent the different operational features within the cell from which a simulation model was designed within Simulink®. Numerous EEC designs were created and compared using RelaxIs®. The closest fit to the theoretical cell response resulted in the optimal EEC circuit utilised for cell characterisation. Thus, by incorporating the optimal EEC in the Simulink® simulation model, the voltage and current signalsmeasured during each experiment could be added to the model. The measured voltage was used to generate a simulated current from the EEC, which was compared to the measured current. Utilising Response Optimizer®, the EEC parameters were calculated based on the model results by minimising the error between the simulated and measured current.

The dissertation verifies and validates that the CI method is a suitable characterisation method delivering EEC results that are closely correlated with electrochemical impedance spectroscopy (EIS) performed under similar experimental conditions.