Study on the Operation of the LUTsCO2 Test Loop with Pure CO2 and CO2 + SO2 Mixture Through Dynamic Modeling

Within the framework of the Horizon 2020 DESOLINATION (DEmonstration of concentrated SOLar power coupled wIth advaNced desAlinaTion system in the gulf regION) project, CO₂-based mixtures will be used as the working fluid of the power cycle coupled with the desalination plant. Desalination technologies require temperatures above 50℃, therefore a fluid with a critical temperature above 70 ℃ is required to perform the compression step in the liquid phase, minimizing compression work and increasing cycle efficiency. Blending CO₂ with other fluids, such as SO₂, leads to an increase in the critical temperature of the mixture and makes it suitable for transcritical cycles in concentrated solar power applications, while preserving the advantages of pure CO₂ over steam cycles. Throughout the DESOLINATION project, CO₂ blends will be tested in the LUTsCO2 test loop to provide validation data for the design of heat exchangers. In this work, the adaptation of the test loop to the CO₂ blend is investigated. A dynamic model of the test loop is built in MATLAB-Simulink, which allows each component to be modeled independently and to realize a closed-loop cycle model coupled with a controller and real gas property tables. Steady-state simulations of the system are performed and the dynamic model of each component is verified with the design values. As a result, the study highlights the key performance and fluid dynamic differences which arise from the use of a CO₂ blend instead of pure CO₂.