Techno-economic assessment of low-grade geothermal heat-driven ejector refrigeration cycle with a flash chamber and a booster compressor

In the present study, an ejector refrigeration cycle with a flash chamber (FC) and a booster compressor is proposed to produce a 300-kW refrigeration effect for evaporator temperature varying between - 10 and 0 degrees C. R600a and R1234yf are considered as the working fluids. Readily available geothermal water at 95 degrees C is considered as the heat source. Thermodynamic and economic analyses are conducted by comparing with a vapour compression refrigeration cycle (VCRC) with a FC. It is observed that there exist optimum combinations of booster compressor pressure ratio and flash pressure ratio corresponding to the maximum mechanical COP and minimum levelized cooling cost (LCC). Both the proposed ejector refrigeration cycle and the VCRC yield better economic performance with R600a. For zero-carbon pricing and the specified range of evaporator temperature, the achievable LCC reduction with the R600a-based proposed cycle varies between 11.99 and 13.98%. The corresponding range of the achievable LCC reduction is 15.02-26.20% for a carbon price of $ 75/ton of CO2. If the geothermal water flow rate is restricted to 15 kg/s, the achievable range of LCC reductions for an R600a-based system will be 7.48-10.40% if the carbon pricing is ignored. For a reasonable carbon price, the proposed geothermal heat-driven cycle with each considered working fluid yields a much lower LCC compared to that of the conventional cycle as the annual carbon foot print of the presented cycle is much lower.