Performance evaluation and working fluid selection of combined heat pump and power generation system (HP-PGs) using multi-objective optimization

This study proposes a novel heat pump and power generation integrated system (HP-PGs) that uses a scroll machine as both the compressor and expander. To find the appropriate working fluid for the HP-PGs system, eight kinds of working fluids are selected for performance comparisons. A mathematical model of HP-PGs is established to analyze the energy, exergy, economy and environment performance. Results of theoretical calculation show that the optimal system coefficient of performance (COP) and thermal efficiency are achieved with R141b. R1233zd(E) is the optimal environmental-friendly working fluid considering the climate change and ozone depletion. Additionally, the capital investment cost of the HP-PGs varies oppositely to the payback period. In order to identify the minimum capital investment cost and payback period of HP-PGs, the operating condition of each of the eight working fluids is optimized by the multi-objective optimization (MOP). TOPSIS (Technique for Order Preference Similarity to Ideal Solution) decision-making method is used to search for the optimal results on the Pareto frontier. It is concluded that the payback period and capital investment cost from the MOP results are better than those from the single objective optimization (SOP).