Energy and exergy analyses of a parabolic trough concentrated solar power plant using molten salt during the start-up process

Daily start-up is the character of concentrated solar power (CSP) plants because of solar energy intermittency. Thus, much energy is consumed during the start-up process of CSPs plants. Detailed energy and exergy analyses on the start-up process can guide CSP design and operation. In this study, energy and exergy analyses for parabolic trough concentrated solar power plants using molten salt during start-up processes were conducted, and the distributions and causes of energy loss were investigated. Results indicate that the total start-up energy loss accounts for 52.32% of total input energy. Collector optical loss, turbine cold source loss, and receiver heat loss are major ones, accounting for 45.80%, 23.11%, and 17.91% of the total energy loss, respectively. The exergy loss of the entire start-up process accounts for 67.11% of the total input exergy. Collector exergy loss due to optical efficiency and receiver exergy loss due to heat loss are major ones, accounting for 77.74% and 9.19% of the total exergy loss, respectively. Compared with recirculating pump utilization, utilizing the molten salt anti-freezing solution of the low-load regenerative heater can reduce start-up energy consumption. This work can lay a foundation for the energy-saving optimization of CSP plants during start-up processes. •Energy and exergy analyses on CSPs during start-up processes are conducted.•The distributions and causes of start-up energy loss for CSPs are investigated.•The avoidable energy loss of CSPs during the start-up process is obtained.•The energy consumptions of two molten salt anti-freezing solutions are compared.•Utilizing the low-load regenerative heater could reduce start-up energy consumption.