Hydrocarbons (HCs) are eco-friendly and low-cost, and present an attractive prospect to be widely used in organic Rankine cycle (ORC) systems. However, the existing studies are scattered, and most of optimizations and selections only focus on a single performance index. This study carried out an optimization and selection of hydrocarbons for the subcritical ORCs based on multiple evaluation indexes. The heat source was 100-200oC, and five common hydrocarbons were selected as the working fluids. The selection guidelines of optimal working fluids were provided for various evaluation indexes. Results show that R290, R600a, and R600 achieve the largest net power output for heat sources of 100-150oC, 160-180oC, and 190-200oC, respectively. The system efficiency of R601 is the largest. R290, R600a, and R600 obtain the lowest specific investment cost for heat sources of 100- 140oC, 150-160oC, and 170-200oC, respectively. Compared with R245fa, hydrocarbons can achieve larger system efficiency and lower specific investment cost, and the net power output is also larger for heat sources not exceed 180oC.
Keywords organic rankine cycle (ORC), hydrocarbon(HC), low grade energy, multi-objective optimization, working fluid selection