Life cycle greenhouse gas emission assessment of solar power tower plant based on supercritical CO2 cycle operating at peak-shaving scenarios

Solar power tower (SPT) plants based on supercritical CO2 (S-CO2) Brayton cycles offer promising potential for high-efficiency, large-scale, and flexible peak-shaving in hybrid renewable systems. However, most environmental assessments focus on standalone operation, failing to reflect greenhouse gas (GHG) emission characteristics under peak-shaving scenarios. This study employs life cycle assessment (LCA) to evaluate GHG emission intensity of SPT plants operating within PV-wind-SPT system, and compares it with standalone scenarios to reveal emission mechanisms of peak-shaving operation. Furthermore, the impacts of key design parameters, namely solar multiple (SM) and thermal energy storage (TES), on emission intensity are also examined. Results indicate that peak-shaving SPT plants exhibit higher sensitivity to design parameters and greater potential for emission reduction. Increasing TES capacity notably improves generation performance and lowers emission intensity. Compared to standalone operation, annual electricity generation under peak-shaving decreases by 5.57 %–38.67 %; however, decreased downtime reduces auxiliary grid power consumption and emissions. Increasing TES can significantly improve electricity generation and cut emission intensity by 19.37 %–53.54 %, with a maximum reduction of 17.79 gCO2eq/kWh observed when SM = 3.2. However, the marginal benefits of expanding TES gradually diminish, indicating the need for a comprehensive assessment on TES sizing. As SM and TES increase, main emission contribution shifts from operational phase to production phase. For peak-shaving SPT plants, optimizing TES can reduce the share of operational-phase emissions from over 40 % to approximately 20 %, with absolute emissions reduced by more than 70 %. These findings provide critical insights for the low-carbon design of peak-shaving SPT plants.