Repurposing PEM electrolyzers as active power sinks to recover curtailed photovoltaic energy as green hydrogen in active distribution networks

High-penetration photovoltaic (PV) generation in active distribution networks produces large volumes of curtailed surplus energy while stressing voltage and losses. A battery alone cannot absorb persistent midday surpluses beyond its finite capacity, and prior hydrogen–battery studies have over-attributed battery-protection benefits without a fair comparison. This paper tests whether a proton-exchange-membrane (PEM) electrolyzer operated as an active power sink can recover otherwise-curtailed PV energy into sellable green hydrogen. A stochastic two-stage co-optimization framework couples a non-dominated sorting genetic algorithm (NSGA-II) for siting and sizing with a linear-programming (LP) dispatch on the IEEE 33-bus network, using measured Benban PV Geographical Information System (PVGIS) irradiance, EgyptERA tariffs, and K-means clustering into nine representative days. The proposed system reduces active power losses by 38.8% and produces 127,448 kg/yr of green hydrogen (displacing about 1,000 t CO₂/yr) by cutting daily curtailment from 44.77 to 27.16 MWh. Under a fair comparison with identical degradation-aware dispatch and an identical smart-inverter rating, the minimum voltage (0.9549 p.u.) and battery degradation cost ($20.76/day) match a battery-only system: voltage support comes from the shared IEEE 1547–2018 smart inverter, whereas the electrolyzer’s distinct value is bulk curtailment recovery. Direct hydrogen sales at $2.0/kg dominate re-electrification across a $0.83–$2.56/kg range, driving the fuel cell to its minimum rating (electrolyzer/fuel-cell ratio 18.52). On a full-cost basis (O&M, stack replacement, compression) the levelized cost of storage is $0.978/kWh and of hydrogen $2.78/kg; hydrogen revenue offsets about 72% of the hydrogen-subsystem cost, making the electrolyzer a substantially self-financing grid-support asset.