Introduction

The invention proposes the use of a CO2-based mixture for power generation. Thanks to the addition of thermo-chemically stable compounds, it is possible to reach maximum cycle temperatures higher than ORC (Organic Rankine Cycle) cycles. The mixture is characterized by having a critical temperature higher than that of CO2, this allows obtaining higher performance than the supercritical CO2 cycles (S-CO2).

Technical features

The invention relates to CO2 mixtures with one or more compounds selected in the group which comprises TiCl4, TiBr4, SnCl4, SnBr4, VCl4, VBr4, GeCl4 and metal carbonyls for applications in the production of electrical and / or thermal power. The additional compounds are present in the mixture with a concentration between 1 and 30% molar. The addition allows having a mixture with a critical temperature higher than that of CO2, thus obtaining a liquid fluid up to 40-50 °C and thermodynamically stable at temperatures of 400 °C or higher without significant alterations and without causing undesirable degradation products. Typically, the heat recovery from low-temperature sources is obtained by means of ORC, which can reach 300-350 °C as the maximum temperature of the cycle due to the thermal stability of the organic fluids. The common sizes are from dozen of kW to dozen of MW. For higher powers can be successfully applied the steam cycles; for high-temperature sources, but with small/medium size plants the performances are not as good as what can be obtained with a CO2 supercritical cycle. The invention, which foresees the mixing of specific substances with CO2, allows the obtaining more efficient thermodynamic cycles.

Possible Applications

• Production of electricity from sources with limited power;
• Production of electricity from renewable sources (solar, geothermal);
• Production of thermal energy;
• Replacement of ORC cycles;
• Replacement of cogeneration engines;
• Refrigeration systems.

Advantages

• Greater efficiency compared to pure CO2 based cycles;
• Greater efficiency compared to cycles with ORC engines;
• More efficiency than steam cycles for small to medium sizes;
• Maximum cycle temperatures higher than those of cycles operating with organic fluids.