Techno-economic Optimization of Hybrid PV–CSP Plants with Supercritical CO2 Power Cycles

QC 20260508

Abstract

Concentrating Solar Power (CSP) plants are a promising technology for decarbonizing the electricity grid due to their ability to integrate cost-effective Thermal Energy Storage (TES) and provide dispatchable solar electricity. However, their deployment has been constrained by comparatively high Levelized Cost of Electricity (LCOE) and by the reliance on large plant sizes to achieve cost competitiveness, resulting in high capital requirements and limited deployment flexibility. Improving power-cycle efficiency and enabling cost-effective operation at smaller scales therefore emerge as key requirements for enhancing CSP competitiveness.

Supercritical CO2 (sCO2) power cycles, high-temperature thermal energy storage technologies, and hybridization with photovoltaic (PV) generation provide complementary pathways to address these limitations. Supercritical CO2 cycles reduce performance penalties at small scales (10 MWe) and enable higher thermodynamic efficiencies at elevated temperatures. However, realizing these efficiency gains requires advanced heat transfer fluids and high-temperature TES media beyond conventional molten-salt systems. In parallel, PV hybridization enables low-cost daytime electricity production, complementing CSP-based generation and improving overall system economics. Together, these approaches provide a pathway toward cost-competitive, dispatchable solar power systems.

This thesis investigates how these technologies can be systematically combined through a system-level techno-economic framework. An integrated modeling tool—MoSES (Modeling of Sustainable Energy Systems)—is developed to perform annual performance simulations, dispatch optimization, and multi-objective techno-economic optimization of hybrid PV–CSP and power-to-heat-to-power (P2H2P) systems across different scales, locations, and operating conditions.

Results show that active PV hybridization—i.e., including an Electric Heater (EH) for charging the thermal energy storage —improves CSP performance, reducing LCOE by 22% at 10 MWe, and 14% at 100 MWe, while increasing economically viable capacity factors to 75–85%. The integration of sCO2 power cycles further enhances competitiveness, reducing LCOE by 40–45% at 10 MWe and enabling economically viable sub-50 MWe CSP plants with reduced capital intensity and improved bankability. At larger scales (100 MWe), sCO2 cycles remain advantageous by enabling higher operating temperatures and improved thermodynamic performance.

Transitioning beyond molten-salt systems, high-temperature CSP architectures significantly improve performance. Particle-based hybrid PV–CSP systems achieve LCOE reductions of 25–30% relative to molten-salt configurations, reaching values around 72 EUR/MWh at capacity factors near 80% at 10 MWe. In high-DNI regions, capacity factors exceed 90%, with further LCOE reductions of approximately 20%. These results highlight the strong coupling between operating temperature, power-cycle efficiency, and system-level competitiveness.

Extending the analysis beyond CSP-specific configurations, power-to-heat-to-power systems shows that high-temperature TES combined with sCO2 power cycles minimizes the levelized cost of storage over a wide temperature range. The results show that charging cost and power-block performance dominate system economics. From a system perspective, P2H2P solutions occupy an intermediate competitiveness domain, bridging the gap between PV–BESS systems, which are optimal at low capacity factors (up to 30%), and hybrid PV–CSP systems, which emerge as the preferred solution for high-dispatchability operation (>60%).

Overall, this thesis establishes a coherent techno-economic design framework in which PV hybridization, advanced TES media, and sCO2 power cycles act as complementary technologies, enabling cost-competitive and highly dispatchable solar power systems for future low-carbon electricity systems.

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