Advanced Low Pressure Cycle for Concentrated Solar Power Generation

Turbine inlet pressures of ∼ 300 bar in case of CO₂ based cycles call for redesigning the cycle in such a way that the optimum high side pressures are restricted to the discharge pressure limits imposed by currently available commercial compressors (∼150 bar) for distributed power generation. This leads to a cycle which is a combination of a transcritical condensing and a subcritical cycle with an intercooler and a bifurcation system in it. Using a realistic thermodynamic model, it is predicted that the cycle with the working fluid as a non-flammable mixture of 48.5 % propane and rest CO₂ delivers ∼37.2 % efficiency at 873 K with a high and a low side pressure of 150 and 26 bar respectively. This is in contrast to the best efficiency of ∼36.1 % offered by a transcritical condensing cycle with the same working fluid at a high side pressure of ∼ 300 bar.