Economic Analysis of Organic Rankine Cycle Using R123 and R245fa as Working Fluids and a Demonstration Project Report

Abstract

The organic Rankine cycle (ORC) is a popular technology used in waste heat recovery and low-grade heat utilization, which are two important measures to solve the problems brought by the energy crisis. The economic performance of ORC system is an important factor affecting its application and development. Therefore, the economic analysis of ORC is of great significance. In this study, R123 and R245fa, two frequently-used working fluids during the transition period, were selected for calculating and analyzing the economic performance of an ORC used for recovery of waste heat with a low flow rate and medium-low temperature. Five traditional economic indicators, namely total cost, net earnings, payback period, return on investment, levelized energy cost, and present value of total profit in system service life, which is a relatively new indicator, were used to establish the economic analysis model of ORC. The variation effects of evaporation temperature, condensation temperature of working fluid, flue gas inlet temperature, and mass flow rate of flue gas on the above six economic indicators were analyzed. The results show that the optimal evaporation temperature of R123 is 125 °C, the optimal condensation temperature is 33 °C, and the optimal heat source temperature is 217 °C. For R245fa, the optimal evaporation temperature is 122 °C, the optimal condensation temperature is 27 °C, and the optimal heat source temperature is 177 °C. The economic performance of an ORC demonstration project was reported and used for comparison with the estimation and analysis. It was found that the single screw expander has an excellent economy performance, which greatly reduces the proportion of expander cost in the ORC system.

Zeotropic Mixture Selection for an Organic Rankine Cycle Using a Single Screw Expander

“…Therefore, net work and thermal efficiency are adopted as the first two indicators for evaluating the performance of ORC using single screw expander with zeotropic mixture as working fluid. The third evaluation indicator is heat exchange load of condenser because it is the critical for calculating the cost of condenser that greatly influences the cost and economic performance of entire ORC system [21].…”

“…Expander is the critical device in an ORC system because it significantly affects thermodynamic performance of an ORC system and its cost ranks second in total system investment [21]. It includes turbo type and positive-displacement type.…”

“…The output power of the demonstration project is 11 kW. Considering that R123 will be eliminated in the near future due to environmental factors, a selection of a pure working fluid for ORC using a single screw expander was conducted in our previous paper [21]. It is found that cis-butene may be the best candidate for working in a subcritical cycle.…”

“…On this basis, zeotropic mixture selection for ORC using single screw expander is conducted based on five indicators, namely net work, thermal efficiency, heat exchange load of condenser, temperature glide in evaporator, and temperature glide in condenser. be eliminated in the near future due to environmental factors, a selection of a pure working fluid for ORC using a single screw expander was conducted in our previous paper [21]. It is found that cisbutene may be the best candidate for working in a subcritical cycle.…”

Working Fluid Selection for Organic Rankine Cycle Using Single-Screw Expander

“…R1234yf and R1234ze are two typical HFO working fluids that have recently been studied and are being used frequently [4][5][6][7]. As far as the economic performance of a practical ORC system is concerned, the investment required by the heat exchanger accounts for the largest proportion, followed by that for the expander, and the working fluid accounts for the third [8]. The first two investments are significantly influenced by the characteristics of the working fluid.…”