Firm power generation with photovoltaic overbuilding and pumped hydro storage

The term “firm power generation” is synonymous with “effectively dispatchable solar power.” Indeed, solar power is variable by nature but can be firmed up through various technologies, such as storage, generation blending, or demand response, which can modify the generation and/or load profiles such that they eventually coincide with each other. In this work, two major innovations are presented. First, by virtue of its long-term storage capacity, pumped hydro storage (PHS) is proposed as a viable alternative to conventional battery storage. Second, contrary to traditional practices that minimize curtailment, photovoltaic (PV) systems are deliberately overbuilt and proactively curtailed. Both strategies are demonstrated to reduce the overall cost of firm energy systems. From a modeling perspective, it is argued that the simplified PV and PHS modeling could lead to an overconfident configuration. To that end, a refined configuration model, which integrates the model-chain-based solar power curve for PV and nonlinear hydraulic losses for PHS, is presented. A case study in northern China demonstrates that the simplified PV and PHS models tend to underestimate the equivalent annual cost of the system by 5.79%. Notably, the optimal system configuration suggests an overbuilding ratio of 1.33, validating the effectiveness of overbuilding and proactive curtailment. Additionally, when 5% of peak load is shifted to periods of low demand, the system cost remains nearly unchanged, highlighting the role of PHS in providing long-term storage capacity.