Thermodynamic performance evaluation of a solar powered Organic Rankine cycle (ORC) and dual cascading vapor compression cycle (DCVCC): Power generation and cooling effect

Abstract

The organic Rankine cycle (ORC)−dual cascading vapor compressor cycle (DCVCC) system, being a highly efficient energy utilization technology, possesses significant potential for development. This paper presents a thermodynamic analysis of a new combined ORC and DCVCC system propelled by the solar cycle to produce electric energy and a cooling effect. An exergy-energy evaluation was conducted utilizing six distinct pairs of refrigerants due to their favorable thermodynamic properties, efficiency, environmental considerations, compatibility, safety, and regulatory compliance, namely R245fa-R114, R245fa-R1234yf, R245fa-R1234ze, R245fa-R32, R245fa-R404A, and R245fa-R134a. The fixed refrigerant pair R245fa-R114 is used in the ORC-VCC₁ circuit, while the remaining pairs of refrigerant are used in the VCC₂ circuit. The system modeling is done using the Engineering Equation Solver (EES) program, which takes into account all assumptions, boundary conditions, and inputs as well as the built-in thermodynamic characteristics of various refrigerants in the suggested system models. The findings show that the thermal efficiency of the proposed system exhibits an 84.84% improvement compared to a conventional ORC. This study investigates the influence of thermodynamic parameters, specifically turbine inlet temperature, turbine inlet pressure, and condensing temperature, on the overall performance of the system. The refrigerant pair of R245fa-R32 has a 14.53% higher COP compared to the R245fa-R114 pair when subjected to variations in turbine inlet temperature. A notable enhancement in thermal and exergy efficiency has been reported, exhibiting an increase of 3.03% and 2.03%, respectively, compared to the simple ORC-VCC configuration. The application of R32 in the VCC₂ circuit results in a 63% enhancement in cost-effectiveness as compared to R114. However, low-GWP refrigerants like R1234yf and R1234ze boost COP by 55.45% over R114. In addition, the elevating of the condensing pressure results in a decrease in the COP, thermal efficiency, and net work. Moreover, by finding the most favorable range of evaporator temperature that maximizes the benefits in both cycles, improves system performance characteristics including COP, thermal efficiency, net-work, and refrigerant mass flow rate. For instance, at higher evaporator temperatures the usage of R1234yf, and R1234ze generates approximately 16% higher COP than R114 refrigerant which is making sure the reliability and efficient use of low GWP fluids.