CFD Application for the Study of Innovative Working Fluids in Solar Central Receivers

Concentrating solar thermal (CST) technologies are focused on the production of both electricity and heat by the concentration of a direct beam part of the sunlight. Thus, solar thermal electricity (STE) plants collect and concentrate the solar energy which is converted into heat using a heat transfer fluid (HTF) in the solar receiver, and, in a second step, the heat is transformed into electricity by a power block. The selection of an appropriate HTF is important for increasing both the solar receiver efficiency and that of the overall STE plant. In addition, the solar receiver relative cost can be minimised by the selection of an HTF capable of achieving higher temperatures or, as a result, higher receiver efficiencies. A higher working fluid temperature is associated with a greater thermal efficiency in both receiver and power cycle if a suitable HTF and receiver design are defined. Commercial HTFs present some limitations that do not allow the improvement of thermal efficiencies in STE plants. Therefore, innovative HTFs should be studied to enhance the facility performance. This chapter is focused on the evaluation of a new HTF (supercritical CO₂) used in a solar central receiver compared to a commercial one (molten salt) using a CFD model. In this context, the results related to the operating conditions for the innovative HTF and to the adaptation of the solar receiver design have been discussed and analysed.