Evaluation of R-1234ze(Z) as drop-in replacement for R-245fa in Organic Rankine Cycles – From thermophysical properties to cycle performance

• Comparison of the relevant thermophysical properties of R-1234ze(Z) and R-245fa.
• Study on R-1234ze(Z) as drop-in replacement for R-245fa in low-grade ORC processes.
• Heat source temperature range from 100 °C to 250 °C, relevant for industrial applications.
• Optimized operation points for stationary cycle model of typical ORC configuration.

To Prof. Jürgen Köhler to his 60th birthday.ORCs (Organic Rankine Cycle) experience growing interest for the generation of electricity from industrial waste heat. However, the widely used working fluid R-245fa does not seem to be sustainable due to its relative high GWP (Global Warming Potential) of almost 900 [1]. In this work, we have evaluated the low GWP working fluid R-1234ze(Z) as drop-in replacement for R-245fa in low-grade ORC processes. Our studies thereby comprise a comparison of the thermophysical properties of R-1234ze(Z) and R-245fa and resulting differences in the performance of the ORC cycle. Information on the thermophysical properties of R-1234ze(Z) from experiment is complemented by molecular simulation results.Our system simulation studies on the ORC process covers a heat source temperature range from 100 °C to 250 °C, which represents relevant operating conditions for industrial applications. A stationary cycle model of a typical ORC configuration was set up in order to optimize operation points and to evaluate characteristic system values for both working fluids.Our simulation results indicate that R-1234ze(Z) is a promising replacement fluid for R-245fa in ORC applications, though noticeable performance losses for heat source temperatures between 183 and 224 °C are observed.