Abstarct: low temperature heat sources and heat losses by Rankin organic cycle, we can reduce the use of fossil fuels.Finding the best working fluid in terms of efficiency, net production and exergy efficiency can help us further in using these resources.In the study, r218 operating fluids are among the selected fluids for Rankin organic cycle with low heat sources.According to the optimization performed for R218,RC318,R115,R125 fluid in solar renewable cycles, geothermal, biomass and heat recovery were calculated 71.6838%,71.0385%,71.0991%,65.0385% respectively.