Calculating active power for water electrolyzers in dynamic operation: Simple, isn’t it?

Calculating the power consumption of water electrolyzers is a seemingly simple task. Yet, when the supplied current varies periodically in time, careless usage of simple equations can lead to tremendously erroneous results. These fluctuations in the supplied current are more or less reality in all industrial power electronic rectifiers. In this short communication, we will show mathematically how forgetting to include the power components inflicted by the fluctuating current or using simple equations defined for zero-centered, sinusoidal alternating currents causes incorrect results in the case of water electrolyzers with a fluctuating current supply. Our goal is to remind the scientific community of the importance of using accurate mathematical definitions of active power, along with appropriate measurement setups, to avoid significant errors in determining one of the key performance indicators of water electrolyzers.