OPTIMIZATION OF A NEW CONFIGURATION OF POWER TRI-GENERATION CYCLE BY THE USE OF A MULTI-PURPOSE GENETIC ALGORITHM

Bardia Eftekhari̇,Mehdi Ali̇ehyaei̇

doi:10.18186/thermal.726076

Abstract

In the current study, a new configuration of power tri-generation cycle was suggested. In this cycle, the energy of hot gases output from the gas cycle in the heat recovery steam generator (HRSG), and the waste energy of the condenser in the steam cycle were recovered in the Organic Rankine Cycle (ORC). After the energy, exergy, and economic modeling of the cycle, the optimization of this cycle by the use of multipurpose genetic algorithm was performed. The objective functions were the electricity cost and the second law efficiency of thermodynamics. The variables chosen for optimization were the air to fuel molar ratio, the compression, and expansion ratio of the compressor and turbine of the gas cycle, the mass flow rate of water steam and refrigerant in steam cycles and ORC, the Pinch points between the gas cycle and steam, and steam cycles and ORC, and the maximum temperatures of the steam and ORC cycles. The optimization results showed that by choosing the optimal values of variables, the efficiency of the first and second thermodynamic laws, and the produced entropy would be 67.3%, 68.9%, and 3342.5 kW/K. Also, the generated electricity cost was reduced to 0.049 US$/kWh.

Highlights

The renewable energy sources such as solar energy, geothermal energy, and a large amount of the heat waste in different industries, can be a potential source for meeting the demands of a part of world’s energy consumption
The heat exhausted from the condenser in steam cycle, can be recovered in Organic Rankine Cycle (ORC)'s evaporator [18].Carcasci et al.in 2014 proposed a Thermodynamic analysis of an organic Rankine cycle for waste heat recovery from gas turbines their investigate showed cyclohexane is the best fluid for low oil temperature, benzene is the best choice for medium oil temperature and toluene should be used for high oil temperature
The written M-Files Xsteam and Refprop were used for thermodynamic specifications of the steam and working fluids of the cycle [47] .For validation of the model, since the cycle proposed in the current study have not been presented in any other studies so far, the gas turbine cycle and the single-pressure heat recovery steam generator (HRSG) are investigated

Summary

INTRODUCTION

The renewable energy sources such as solar energy, geothermal energy, and a large amount of the heat waste in different industries, can be a potential source for meeting the demands of a part of world’s energy consumption. Six working fluids and four types of ORC were studied [15].Darvish et al in 2015,simulated the thermodynamic performance of a regenerative ORC which used a low-temperature heat source to help with the selection of proper organic working fluid They use the thermodynamic models to investigate thermodynamic parameters such as ORC’s output power and energy efficiency. The heat exhausted from the condenser in steam cycle, can be recovered in ORC's evaporator [18].Carcasci et al.in 2014 proposed a Thermodynamic analysis of an organic Rankine cycle for waste heat recovery from gas turbines their investigate showed cyclohexane is the best fluid for low oil temperature, benzene is the best choice for medium oil temperature and toluene should be used for high oil temperature.

HRSG 8 Steam turbine 9 Condenser

RESULTS AND DISCUSSION

CONCLUSION