Power quality estimation of water electrolyzers based on current and voltage measurements

Abstract

The ripple of the supplied direct current has a significant effect on the energy efficiency of the water electrolyzer cell. Hydrogen production is defined by the current mean value, but current harmonics generate additional losses in the electrolyzer cell. However, the direct measurement of the DC current in the kiloampere range may be a challenging task compared with the voltage, which is practically in the range of a few hundreds volts in the electrolyzer stack. The effect of current harmonics on the energy efficiency and the voltage mean and root-mean-square (RMS) values is analyzed analytically based on the measured polarization curve of the PEM electrolyzer cell. The results show that both in the case of a theoretical sinusoidal current ripple and a practical thyristor bridge supply, the voltage mean or RMS values do not give a reliable estimate of the power quality. Instead, the voltage waveform as a function of time or the difference between the current mean and RMS values should be monitored.