Evaluation and optimization of organic Rankine cycle (ORC) with algorithms NSGA-II, MOPSO, and MOEA for eight coolant fluids

E Ghasemian,M A Ehyaei

doi:10.1007/s40095-017-0251-7

Abstract

In this study, a simple organic cycle for eight subcritical coolant fluids has been studied thermodynamically and economically. For all the coolants, the present cycle was optimized for the best thermal and exergy efficiencies and the best cost of energy production. In a multi-purpose procedure, using the three methods NSGA-II, MOPSO, and MOEA/D, design variables in the optimization are the inlet turbine pressure and temperature, the pinch temperature difference, the proximity temperature difference in regenerator exchanger, and condenser temperature difference. The optimization results show that, in all three methods, the impact of the parameters’ inlet turbine temperature and pressure on the three objective functions is much more than other design parameters. Coolant with positive temperature gradients shows a better performance but lower produced power. In optimization methods, among all the coolants, the MOPSO method showed higher thermal and energy efficiency, and the MOEA/D showed lower production power costs. In terms of the rate of convergence, also both the MOPSO and NSGA-II methods showed better performance. The fluid R11 with the 25.7% thermal efficiency, 57.3% exergy efficiency, and 0.054 USD cost per kWh showed the best performance among all of the coolants.

Highlights

The increasing consumption of fossil fuels causes greenhouse gas emissions, global warming, and environmental degradation
In the last 20 years, the use of organic Rankine cycle instead of a simple Rankine cycle has been considered The operating ORC power plants around the world, with capacities ranging from 200 kW to 130 MW, demonstrate special attention to this technology
At any stage, with assumption that four design variables are fixed, a variable is changed in a specific range and its effect on thermal efficiency, exergy efficiency of the cycle, and the production cost per each kWh of energy is studied and analyzed

Summary

Introduction

The increasing consumption of fossil fuels causes greenhouse gas emissions, global warming, and environmental degradation. Darvish et al [7] simulated the thermodynamic performance of a regenerative organic Rankine cycle that uses low-temperature heat sources They made use of thermodynamic models to evaluate the thermodynamic parameters such as power output and energy efficiency of ORC. Ashouri et al [2] studied an ORC in terms of thermodynamics and economic for power generation with a small-scale up to 100 kW This parametric study indicated the impact of key parameters such as temperature and turbine inlet pressure on the parameters of the system such as network, thermal efficiency, oil and total heat transfer coefficient, the heat transfer area of the thermal exchangers of the shell and tube, as well as the system costs. The current cycle was optimized for the best exergy and thermal efficiency as well as the best production cost in a multi-objective functions, using the three methods NSGA-II, MOPSO, and MOEA/D. This algorithm was first introduced by Zhang and Li [24]

Results and discussion

Number of neighbors 10

Conclusion