Hybrid electrolyzer systems: Smart strategy or economic fallacy?

Hybrid electrolyzer systems combining alkaline water electrolysis and proton exchange membrane water electrolysis have been investigated based on the expectation that their contrary techno-economic characteristics may compensate for the individual limitations of each technology. Such a combination is therefore expected to improve the profitability of green hydrogen production. To reassess the economic potential of hybrid electrolyzer systems beyond these technology-specific assumptions, we independently vary two key characteristics, electrolyzer investment cost and efficiency, in a large-scale sensitivity analysis. For each generated parameter configuration, we performed a techno-economic optimization of a green hydrogen supply chain, including two electrolyzers. The resulting system design, cost objective, and dispatch behavior are subsequently analyzed. Consequently, hybrid electrolyzer systems are identified as optimal if they provide a cost benefit over single electrolyzer systems. The analysis reveals that hybrid electrolyzer systems represent the optimal solution in at most 5% of the investigated cases. Furthermore, the maximum cost benefit is 0.057 €/kgH2, which corresponds to only about 1% of the total green hydrogen production cost. Additional analyses considering variations in energy purchase prices, storage fees, renewable energy availability, and baseline electrolyzer efficiency do not substantially alter these findings. Hence, under the investigated system conditions, differences in electrolyzer investment cost and efficiency offer only marginal cost benefits of hybrid electrolyzer systems compared to single electrolyzer systems. They therefore seem more likely to represent an economic fallacy than a smart strategy.