Investigation of CO₂ mixtures to overcome the limits of sCO₂ cycles

¹ Politecnico di Milano, Dipartimento di Energia, Via Lambruschini 4, 20156 Milano, Italy
² Università degli Studi di Brescia, via Branze 38, Brescia, Italy

^* Corresponding author: ettore.morosini@polimi.it

Abstract

Supercritical CO₂ cycles are a promising technology, but their performance drops for hot cold source, in hot and arid environments, typical of a CSP field. The adoption of CO₂-based mixtures as working fluid can turn supercritical CO₂ cycles into transcritical cycles even at high temperatures, with performance improvement and significant power block cost reduction. The concept is addressed within the SCARABEUS project, an EU funded Horizon 2020 project dedicated to the use of CO₂-based mixtures for CSP plants. In this work, the use of the CO₂+C₆F₆ mixture as working fluid for a power cycle coupled with a solar tower is analysed. The potentiality of the mixture is presented, given its very low toxicity and its good thermal stability limits. Comparisons with the sCO₂ cycle is performed for some typical configurations, in order to underline the advantages of the mixture, and a preliminary design of the turbine is presented, developed in a 1D tool.