Experimental Study on a Small-Scale Transcritical CO2 Rankine Cycle for Solar Thermal Applications

Abstract

The supercritical CO2 cycle is one of the next generation’s power generation cycle. Especially, the transcritical CO2 Rankine cycle (TCRC) is a suitable candidate for dispersed generation systems with small-scale solar thermal applications. Compared to other cycle studies applied in other fields such as nuclear energy, there are limited reports on renewable energy fields. Therefore, in this study, the TCRC for a small-scale solar thermal heat source is investigated by thermodynamic and experimental methods. The experimental facility was built with approximately 12 kW of thermal capacity and commissioned to evaluate its performance using a case study. The maximum temperature of the cycle is the primary optimization variable of the experiment, and it has a significant impact on the cycle thermal efficiency. Based on the experimental data, the trends of the cycle thermal efficiency and generated power are simulated assuming that the TCRC is operating with real insolation during the daytime. As a result of the simulation, maximum efficiencies of 6.41 and 6.03% are obtained from maximum solar radiation amounts of 758 and 674 W/m2 in May and June, respectively. At that time, the amounts of power generated were 726 W and 626 W, respectively.