Green hydrogen generation for mitigating the impact of curtailment in floating photovoltaic - pumped hydro energy storage (FPV-PHES) systems

Techno-economic performance of unpredictable renewables is often assessed without considering dispatch limitations over the lifetime. This assumption is increasingly less likely, and generation curtailment can reduce performance and increase the LCOE. This study first examines the efficiency decline and LCOE rise for floating photovoltaics coupled with pumped hydro storage connected to grids with high curtailment levels. Findings confirm that performance degradation is mitigated by enhancing self-consumption. Subsequently, the study explores the integration of a water electrolyzer, which consumes photovoltaic electricity with secondary priority to the pumped hydro, to improve efficiency, reduce LCOE, and produce green hydrogen. Unlike other curtailment mitigation techniques, hydrogen production from excess generation gives the opportunity to decarbonize hard-to-abate sectors. The analysis is conducted considering a pumped hydro energy storage system setup in Sardinia (Italy), integrated with floating photovoltaics and anion exchange membrane electrolyzers of various sizes. The latter are selected to maximize the self-consumption. The results demonstrate that, without the electrolyzer, and in scenarios characterized by high levels of curtailment, these systems could operate at only one-quarter of their first-law efficiency compared to scenarios without dispatch limitations (24 % vs 89 %), while levelized costs could be more than three times higher (280 vs. 80 $/MWh). In contrast, integration of the electrolyzer enables efficiency and levelized costs to be maintained at intermediate levels (61 %, 145 $/MWh, and 8.5 $/kg of hydrogen), with potential for further reductions considering revenues from the provision of grid services. Moreover, adding the electrolyzer sets an upper limit on the levelized cost of the integrated system, making its costs independent of curtailment levels. Furthermore, the electrolyzer can provide demand response to the electrical grid.