SCARABEUS · Supercritical CARbon dioxide/Alternative fluids Blends for Efficiency Upgrade of Solar power plants

The main objective of the SCARABEUS project is the reduction of the CAPEX and OPEX in concentrated solar power technologies by about 32% and 40% respectively, leading to a final cost of Electricity below 96 €/MWh (lower than 30% of the actual value) through an innovative power cycle based on CO2 blends. This cost reduction will be able to close the gap between CSP and other renewable technologies. This project fits in the call ""New cycles and innovative power blocks for CSP plants."" as a brand new power cycle concept will be developed. With respect to state-of-the-art sCO2 cycles, the addition of small quantities of selected elements to pure CO2 (i.e. inorganic compounds and fluorocarbons), known as CO2 blending, can increase the CO2 critical point allowing the adoption of condensing cycle even in typical CSP plant locations. Condensing sCO2 cycles have higher thermal-to-electricity conversion efficiency with respect to conventional steam and sCO2 cycles.In addition, higher maximum operating temperature with respect to steam cycles can be adopted with further efficiency increase. The combination of these two aspects enables drastic reductions of the levelised cost of electricity In the project, CO2 blends stable at temperatures up to 700°C (which corresponds to 100°C above current CSP maximum temperatures) and with a pseudocritical temperature of about 50°C will be investigated. A preliminary screen was performed identifying some potential candidates (i.e. TiCl4). Assuming the simple cycle configuration, the TiCl4-blended CO2 outperforms the cycle using pure CO2 by 5% points at 700°C . When using the advanced sCO2 cycle, the efficiency gain is reduced to 2% points, but with significant cost savings. The proposed CO2 blend will be tested in a loop at 300 kWth scale with typical CSP fluids for 300 hours. Long term stability will be measured for 2000 hours and material compatibility assessed through dedicated experiments.""