Assessment of a solar energy powered regenerative organic Rankine cycle using compound parabolic involute concentrator

A non-imaging concentrator compound by involute and parabolic concentrator was considered in a regenerative organic Rankine cycle (ORC). The concentrator was covered by vacuumed glass tube to reduce heat loss from the absorber, and to extend the effective life-cycle of optical components. Using the non-imaging concentrator can eliminate the necessity of sun tracking system due to its large acceptance angle. A simulation was carried out for low temperature solar thermal electric generation for various working fluids including dry, isentropic and wet fluids. The results showed the best efficiency of concentrator was observed for the case of R-141b and followed by methanol, R-113, water, benzene and cyclohexane, respectively. The best overall system efficiency was seen in the case of R-141b to be 16.7%. The evaporator pressure was changed as a calculation parameter. The best improvement was obtained for water and R-141b to be 8.8% and 8.3%, respectively. R-141b has a preferable performance because of its low boiling point and can be appropriate for small scales. The increase in evaporator pressure persuades the performance improvement for the case of methanol, water and benzene. It proves that these working fluids can be used for larger scale applications with a better thermal performance.