Mixed Configuration of Multi-to-One Alkaline Electrolyzers in Solar Power-to-Hydrogen Plants

To mitigate capital investment costs, the multi-to-one configuration, wherein multiple alkaline electrolyzers share a single balance of plant (BoP) system, is widely adopted in projects. However, compared with the one-to-one configuration, the strong coupling inherent in the shared BoP imposes complex mutual constraints on the on-off switching and load allocation of multiple electrolyzers, thereby compromising the operational flexibility of the hydrogen plant. To leverage the complementary strengths of multi-to-one and one-to-one configurations regarding investment costs and operational flexibility, this paper proposes a mixed configuration method for multi-to-one electrolyzers in solar power-to-hydrogen systems. First, the hydrogen production characteristics, on-off switching, and power allocation of multiple alkaline electrolyzers are modeled. Furthermore, the coupling constraints specific to multi-to-one clusters are characterized based on practical engineering experience. Subsequently, a mixed configuration model targeting the minimization of the levelized cost of hydrogen (LCOH) is proposed. This problem is formulated as a mixed-integer fractional programming (MIFP) model with second-order cone constraints. Meanwhile, the information gap decision theory (IGDT) is applied to address photovoltaic power output uncertainty, and a bounded Dinkelbach algorithm is employed to reduce computational complexity. Case studies based on a real-world project in northern China demonstrate that the proposed mixed configuration model reduces the LCOH by 0.6%, 0.7%, and 1.3%, respectively, compared to uniform four-to-one, two-to-one, and one-to-one configurations. Additionally, the robustness analysis based on the IGDT demonstrates that the mixed configuration achieves the largest tolerable PV uncertainty radius under the prescribed LCOH limits.