Abstract
A model to evaluate the performance of a solar powered regenerative Organic Rankine Cycle (R-ORC) using five dry organic fluids: RC318, R227ea, R236ea, R236fa, and R218, is presented in this paper. The system is evaluated in two locations in the U.S.: Jackson, MS and Tucson, AZ. The weather data for each location is used to determine the heat available from the solar collector that could be used by the R-ORC to generate power. Results from the R-ORC performance are compared with a basic ORC using first and second law criteria as well as primary energy consumption (PEC) and carbon dioxide emission (CDE) savings for both locations. An economic analysis to determine the maximum capital cost for a desired payback period is presented in this paper. A parametric analysis is also performed to study the effect of the turbine efficiency as well as the open feed organic fluid heater intermediate pressure on the system performance. Results indicate that the R-ORC is able to generate more power than the basic ORC for some of the selected working fluids. For the R-ORC, R236ea is the working fluid that show the best performance among the evaluated fluids under the modeled conditions. On the other hand, the basic ORC with R236ea as the working fluid outperformed three of the fluids in the R-ORC. Also, the R-ORC evaluated in Tucson, AZ is able to generate more power, to provide more PEC and CDE savings, and had a higher available capital cost than the R-ORC evaluated in in Jackson, MS.
Highlights
Organic Rankine Cycles (ORCs) have become an area of increased interest and study because of their ability to use heat transfer from low to medium temperature sources to generate power.Various sources of heat can be used to power ORCs such as waste heat, geothermal energy, and solar energy [1,2,3,4,5]
The regenerative Organic Rankine Cycle (R-ORC) evaluated in Tucson, AZ is able to generate more power, to provide more primary energy consumption (PEC) and carbon dioxide emission (CDE) savings, and had a higher available capital cost than the R-ORC evaluated in in Jackson, MS
The working fluid greatly affects the performance of ORCs, fluid selection and performance has been widely studied by several researchers [6,7,8,9,10,11]
Summary
Organic Rankine Cycles (ORCs) have become an area of increased interest and study because of their ability to use heat transfer from low to medium temperature sources to generate power. In a study by Imran et al [22], the authors performed a thermo-economic analysis on a basic ORC, a single stage R-ORC, and a double stage R-ORC They found that of the five fluids they investigated R245fa under the modeled conditions had the lowest specific investment cost, and the evaporator pressure had a significant impact on thermal efficiency and specific investment cost. Rayegan and Tao [32] modeled a solar powered R-ORC that provides electricity for a geothermal air conditioned net zero energy commercial building located in Pensacola (Florida, USA) using TRNSYS software They evaluated 11 fluids and 3 types of solar collectors to determine the optimum combination under the modeled conditions. The performance of the proposed R-ORC is analyzed based on the PEC and CDE savings, and the available capital cost for both locations
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