Frequency-Domain Analysis of Water Electrolysis for Optimal Hydrogen Production under Variable Frequency and Duty Cycle

Abstract This study proposes a novel method to maximize efficiency at various frequencies and duty cycles in hydrogen production through water electrolysis. To analyze the frequency response, we model the water electrolysis as electrical components and assume all electrical components operate within their linear region. To maintain operation in linear region we consider the pulse width which is necessary for electrolysis without formation of the diffusion layer. We modeled the water electrolysis using an innovative electrical circuit to facilitate analysis in the frequency domain. Our assumptions involved typical values for double layer capacitance (Cdl) and charge transfer resistance (Rct) in alkaline electrolysis, particularly in KOH-based systems, which range from 1 to 100 µF/cm² and 0.5 to 20 ohms, respectively. across a frequency spectrum of 0 to 50 kHz. Moreover, we examined the influence of duty cycle on the electrolyzer’s performance by applying Fourier series coefficients. Our investigation of duty cycles at 5%, 10% and 15% revealed that the efficiency is maximized at a 5% duty cycle compared to higher duty cycles. Ultimately, our results demonstrate that achieving optimal efficiency necessitates a careful balance between operating frequency and duty cycle, which is crucial for preventing diffusion layer formation and improving overall system performance.