Mixed energy storage in nuclear and concentrated solar systems: Effects on operations and the economy

Hybrid energy systems that combine nuclear heat sources with concentrated solar power (CSP) can enhance operational flexibility through shared thermal energy storage (TES) and coordinated electricity dispatch. This study develops a techno-economic modeling framework to evaluate a hybrid nuclear–solar thermal power plant architecture in which both heat sources charge a common molten-salt TES system and supply heat to a shared steam turbine. The analysis integrates a mixed-integer linear programming (MILP) dispatch optimization with the System Advisor Model (SAM) to simulate plant performance and determine economically optimal operating schedules under alternative electricity price structures. Economic performance is evaluated using the power purchase agreement (PPA) metric, defined as the minimum electricity price required to achieve a target internal rate of return of 11% over a 20-year project lifetime. Hybrid system benefits are therefore quantified as the relative reduction in required PPA compared with separately optimized nuclear and solar plants operating under identical tariff conditions, providing a consistent economic baseline for comparison. Simulation results indicate that under highly volatile electricity markets such as CAISO price structures sharing TES and turbine infrastructure can reduce the required PPA by up-to approximately 8% relative to standalone plants. This improvement arises primarily from enhanced dispatch flexibility, allowing the turbine to operate closer to its design efficiency while shifting generation toward higher-price periods. The strongest economic synergy occurs when nuclear and solar thermal outputs are comparable. However, under lower-volatility tariff conditions the hybrid configuration may exhibit limited due to turbine part-load efficiency effects and storage utilization constraints. • Hybrid nuclear–solar systems reduce PPA by up to 10% under high volatility. • Synergy peaks when nuclear and solar thermal outputs are comparable. • Shared TES contributes ∼3% of total hybrid performance gain. • Turbine scaling effects account for ∼1% additional economic benefit. • Results are highly sensitive to intraday price spread structure.