Research advance of thermodynamic systems with nonaqueous working fluids applied in low-temperature energy power generation

This paper presents a review of the status of power generation with nonaqueous working fluids from low temperature thermal resource, the features, equipment composition and working processed as well as comparison of two main types of thermodynamic cycles which are Organic Rankine Cycle(ORC) and Kalina Cycle and nonaqueous working fluids including their classification and filter criteria for thermodynamic cycles. Nonaqueous working fluids thermodynamic cycles are applied to the conversion of geothermal energy, low-temperature solar energy, ocean thermal energy and industrial low-temperature waste heat etc. Most of thermodynamic cycle systems for low-temperature thermal resource could be classed as ORC system and Kalina system all of which have respective advantages and limitations. Besides cycle type the working fluids would affect significantly the general efficiency of the entire thermodynamic system. The evaluating indicators for working fluids include critical temperature, critical pressure, global warming potential (GWP) and toxicity etc. as well as system efficiency (exergy efficiency included) for the final evaluation. Based on the advantages and limitations of ORC and Kalina cycle the mixed working fluids are developed and respective thermodynamic cycles illustrate bright prospect.