Our project has reached an important milestone: after an initial screening of promising dopants to be blended with CO2, thermal stability tests of the mixtures were carried out, and material compatibility test were performed for the most interesting blends. As an result, the most interesting CO2 mixtures for the pilot plant were determined.

The DESOLINATION project aims to develop an innovative CSP (Concentrated Solar Power) cycle using CO2 blends together with a heat recovery system to power a desalination plant. The working fluid becomes supercritical CO2-based and the turbomachinery is adapted to new ranges of temperatures and pressures, to be adapted to future CSP plants.

Thermo-chemical stability of the working fluid is one of the most important aspects to be considered for the working fluid selection, especially when dealing with high-grade sources such as concentrated solar power.

The thermodynamics of CO2 blends have been characterised based on experimental data available in the literature as well as with experimental campaign.

Relevant outcomes have been obtained from the test performed on the CO2 mixtures selected after an initial screening: three different dopants have successfully passed the thermal stability test above 550°C with the consolidated methodology developed in the Fluid Test Laboratory of our project partner, the University of Brescia.

However, it is crucial not only that the working fluid avoids chemical dissociation, but also that the interaction between the mixture and the equipment material is acceptable, particularly in the high-temperature sections of the power plant.

For this reason, the two most interesting fluid candidates have been tested in material compatibility test: a prolonged exposure of different material samples at the mixture atmosphere at 550°C, the maximum temperature of the pilot plant, provided interesting results.

The metal samples have been analysed with several methodologies, including mass weight change, optical microscope, and scanning electron microscope.

Our next step will be to test the compatibility of the new materials and coatings with the CO2 mixtures most suitable for the pilot plant. Stay tuned!

Contributors: Paolo Giulio IORA, Gioele Di Marcoberardino and Michele Doninelli (UNIBS)