Superstructure design and optimization on supercritical carbon dioxide cycle for application in concentrated solar power plant

Abstract

A superstructure-based method is applied to optimize the design of supercritical carbon dioxide cycle for concentrated solar power systems. A superstructure is designed for the cycle featuring various options in cold-end and hot-end configurations. Process integration and cycle variables are simultaneously optimized for the superstructure based on the integrated thermoeconomic model of the overall system. Optimizations are performed for eight cases with different designs of maximum and minimum temperatures. Sensitivity analyses are conducted on the design parameters and related capital costs of subsystems of the overall system. 1.5–13.5% reduction in levelized cost of electricity is obtained through the superstructure-based optimization relative to the corresponding base cases. The cost of thermal storage system at optimal condition is significantly surged by 36.3–111.6% when the maximum temperature surpasses 600 °C, which consequently leads to the variation in configuration for the optimal cycle. The minimum levelized cost of electricity is obtained at 600 °C with a reduction of up to 4.1% compared to that at 550 °C. The further increase in the maximum temperature beyond 600 °C will be followed by 8.6%—20.2% rise in the levelized cost of electricity. The improvements in maximum pressure and turbomachinery performance can lead to significant reduction in levelized cost of electricity, especially at high maximum and minimum temperatures. However, these improvements have relatively uneventful effects on the configuration of the optimal cycle. The capital cost of thermal storage system has significant effects on the design of the optimal cycle configuration whereas the variation in the capital cost of cycle system has less eventful effects. The effect of capital cost of cycle system is more dominant than that of the thermal storage system at 550 °C and 600 °C maximum temperatures in terms of levelized cost of electricity, while this situation is reversed as maximum temperature rises higher due to the soaring capital cost of the thermal storage system. The configuration with main compression intercooling or partial cooling design in the cold end and single-turbine design in the hot end is finally suggested for the supercritical carbon dioxide cycle applied in state-of-the-art and next-generation concentrated solar power systems.