Simulation and comparative Thermoeconomic analysis of Central Receiver Concentrated solar plants using air as heat transfer fluid

The latest developments on solar technologies demonstrated that the Solar Central Receiver configuration is the most promising application among Concentrated Solar Plants (CSPs). As an alternative to more traditional working fluids, solar-heated air can also be used in CSPs both as working fluid in a Brayton thermal cycle and to heat water for a Rankine thermal cycle, reducing maintenance operations and providing the power section with a higher degree of flexibility; in this case an auxiliary burner is required to extend the operation during off-sunshine hours without a Thermal Energy Storage. This configuration is adopted in Julich CSP plant, operating in Germany and characterized by a nominal power of 1.5 MW, where air is used as heat transfer fluid in the solar tower and to produce steam for the bottoming Rankine cycle. In this paper, the Julich plant with thermal energy storage has been compared with a hybrid CSP plant using air as working fluidin terms of resources consumption and costs. A thermoeconomic analysis has been performed for all the simulated plants, considering the average year of operation and the same amount of yearly net electricity production. The exergy and exergoeconomic costs of each system product has been derived, and the structure of such costs has been analyzed.