Effect of Converter Topology on the Specific Energy Consumption of Alkaline Water Electrolyzers

Abstract

Water electrolysis will be used to produce renewable hydrogen for energy storage and Power-to-X applications in the future renewable-energy-based energy systems. Therefore, the energy efficiency of hydrogen production will probably become a major issue. In this study, the effect of practical supply power converters on the specific energy consumption of MW-scale alkaline electrolyzers is studied and compared with an ideal DC power supply. The current quality and the stack specific energy consumption are studied in the case of traditional thyristor rectifiers and a transistor-based converter. The stack specific energy consumption is analyzed based on the simulated current waveforms and the electrical equivalent circuit of the electrolyzer stack. It is found that the transistor-based converter offers up to 14% lower electrolyzer stack specific energy consumption than the 6-pulse thyristor rectifier and up to 9.2% lower electrolyzer stack specific energy consumption than the 12-pulse thyristor rectifier as the current varies between 5000 A and 1000 A. The simulated change in the stack specific energy consumption of the MW-scale alkaline water electrolyzer outweighs the losses occurring in the rectifiers. Further, selection of the AC voltage level may have a more adverse effect on the stack specific energy consumption with the thyristor rectifier topologies compared with the transistor-based topologies.

Improved Hydrogen-Production-Based Power Management Control of a Wind Turbine Conversion System Coupled with Multistack Proton Exchange Membrane Electrolyzers

“…Regarding the influence of voltage harmonics on the efficiency of the PEM-EL, this is not directly addressed in literature, although [12] and [26][27][28] investigate this issue for alkaline water ELs. However, some general observations can be made.…”

“…The first requirement is needed to maintain a low pay-back time and to assess the advantage of the storage; it has to be noted that in this application, this must be achieved with a strong reduction of the rectified voltage available, using the turbine to supply the EL. As far as the ripple is concerned, it is known that harmonics superimposed onto the DC current worsen the specific energy consumption of the EL, as well as its reliability [12,[26][27][28]. It is preferable to adopt a power converter with an inherently low harmonic content, since the passive or active filters used to suppress it are bulky [12,30].…”

“…As far as the ripple is concerned, it is known that harmonics superimposed onto the DC current worsen the specific energy consumption of the EL, as well as its reliability [12,[26][27][28]. It is preferable to adopt a power converter with an inherently low harmonic content, since the passive or active filters used to suppress it are bulky [12,30]. The dynamic performance has to fit the power variation meaning that the dynamic behavior of the converter must be faster than the dynamic of the generator to preserve the DC bus capacitor by additional voltage stress.…”

Fractional Charging Converter With High Efficiency and Low Cost for Electrochemical Energy Storage Devices

“…Once the stress factor for each component is calculated, the total CSF is computed as the sum of component stress factors of the same type as in shown in (5).…”

“…Power-to-X (P2X) is a promising option for storing intermittent sustainable renewables and providing clean energy to residential, industrial, transportation users, etc. For example, alkaline water electrolysis (H2, Al and Cl) have a global capacity >100 GW and its demand is growing fast in recent years [3]- [5]. The advantages of hydrogen is that it can be produced locally, and it offers high energy density, long-term scalable storage and low environmental impact.…”