Abstract
The present study investigated energy, exergy and economic analyses on a new triple-cycle power generation configuration. In this configuration, the energy of the exhaust gas and the wasted energy in the condenser of the steam cycle is recovered in the heat recovery steam generator (HRSG) and the evaporator of organic Rankine cycle (ORC), respectively. A computer code was written in MATLAB to analyze the triple-cycle configuration. Validation through this program showed that the highest errors were 5.6 and 7.1%, which occurred in gas and steam cycles, respectively. The results revealed that the highest generated entropy was associated with the combustion chamber and the evaporator in the steam cycle. The first and second laws of thermodynamics efficiencies were improved by roughly 270 and 8%, respectively, through adding each of the steam and organic Rankine cycles. The entropy generated by the cycle increased by roughly 400 and 4% by adding the steam and organic Rankine cycles, respectively. The price of the produced electricity was also reduced by roughly 60 and 70%, respectively, for these two cycles.
Highlights
After the industrial revolution, consumption of fossil fuels begin to grow
An M-File script was written in MATLAB so as to model the triple cycle (GT + heat recovery steam generator (HRSG) + organic Rankine cycle (ORC))
A new triple cycle thermodynamic system was presented in this study
Summary
Consumption of fossil fuels begin to grow. Considering that, the non-renewable energy sources are limited and have harmful environmental impacts such as global warming, efforts were made by the governments and researchers to employ new approaches in order to decrease the demand for fossil fuels. The ORC recovered heat from the micro-turbine exhaust gas within a temperature range of 250 to 300 °C To this end, a gas 100-kWe micro-turbine combined with ORC was assessed, according to the results of which the output power and the combined cycle efficiency were increased by 1.3 and 40%, respectively, compared to the gas micro-turbine [9]. Bahrami et al (2013) investigated the effect of 9 working fluids on the first law efficiency in combined Stirling-ORC power cycle They addressed the environmental problem associated with the different working fluids. Cao and Dai (2017) assessed the power cycle efficiency in combined gas turbine and ORC system under different operating conditions Their results showed that variable-pressure ORCs deliver a better efficiency compared to constant-pressure ORCs [18]. The contributions and innovations of the present study are as follows: – presenting a new thermodynamic cycle to increase the recovered energy; – conceptual comparison between the efficiency of each of the thermal cycles and the triple-cycle power generation system; – extending the first and second laws efficiencies to triplecycle power generation system; – selection of the ORC optimal working fluid in the triplecycle power generation system
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