Since the electric grids are alternating (AC) sources, the role of the power supply is to condition the AC electric power from the grid and supply the electrolyser stack with a DC current and voltage suitable for the electrolysis process .
Besides, the hydrogen production has been measured for currents ranging between 40 and 120 A. Two representative power supplies (a thyristor-based power supply, ThPS, and a transistor-based power supply, TrPS) have been emulated to feed the water electrolyser. The electrolyser energy consumption and efficiency have been measured for both supplies.
In general, the voltage of an electrolytic cell can be expressed by the sum of the contributions of Vrev and the overvoltages caused by the irreversibilities: (8) V cell = V rev + V ohm + V act In Eq. (8), Vohm is the overvoltage caused by the so-called ohmic losses.
The DC voltage level of MW-scale water electrolyzers is typically 200 V–300 V leading to current levels in the kiloampere range, as stated for example in Ref. [ 3 ].
The operating range of the electrolyzer was limited for safety reasons. Thus there are no measured values below DC current value of 3500 A. It can be stated that both simulated reactive power and power factor are in the same range with the measured values.
However, the effect of current ripple on the electrolytic cell lifetime is still a key research question for water electrolyzers, as suggestions that poor power quality might speed up cell degradation are given in the literature [ 8, 9 ].
To identify and quantify the losses in an electrolytic cell, cell voltage is typically studied. Due to the nonlinear behaviour of electrolytic cell voltage at low current densities, and contrary to a case of a purely resistive load, the mean cell …