Abstract
Waste heat recovery plays an important role in energy source management. Organic Rankine Cycle (ORC) can be used to recover low-temperature waste heat. In the present work a sample power plant waste heat was used to operate an ORC. First, two pure working fluids were selected based on their merits. Four possible thermodynamic models were considered in the analysis. They were defined based on where the condenser and evaporator temperatures are located. Four main thermal parameters, evaporator temperature, condenser temperature, degree of superheat and pinch point temperature difference were taken as key parameters. Levelized energy cost values and exergy efficiency were calculated as the optimization criteria. To optimize exergy and economic aspects of the system, Strength Pareto evolutionary algorithm II (SPEA II) was implemented. The Pareto frontier solutions were ordered and chose by TOPSIS. Model 3 outperformed all other models. After evaluating exergy efficiency by mixture mass fraction, R245fa [0.6]/Pentane [0.4] selected as the most efficient working fluid. Finally, every component’s role in determining the levelized energy cost and the exergy efficiency and were discussed. The turbine, condenser and evaporator were found as the costliest components.
Highlights
Designing an optimal energy recovery system has become a hot spot for energy management researches
Strength Pareto evolutionary algorithm II (SPEA II) is a very efficient multi-objective algorithm compared to other alternative approaches
N final solutions obtained from the Strength Pareto evolutionary algorithm (SPEA) II were examined and ordered using the TOPSIS method and the solution with the best score choseand as the best possible solution
Summary
Designing an optimal energy recovery system has become a hot spot for energy management researches. El-Emam and Dincer, 2013 [2] optimized a geothermal ORC based on the heat exchanger’s total surface area parameter and performed an exergo-economic analysis of the system with the heat source temperature of 165◦ Celsius They used Isobutane as the working fluid and reached the energy and exergy efficiency of 16.37% and 48.8, respectively [2]. 2015 [14] used the multi-objective NSGAII optimization algorithm to find the hybrid organic Rankine plant for solar and lowgrade energy sources with the highest first and second law efficiencies and the lowest levelized energy cost They found Cyclopropane as the most efficient working fluids, with a power output greater than 100 kW [14]. The optimization algorithm is introduced, and after that, the results are analyzed
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