Thermoenvironomic optimization of gas turbine cycles with air preheat

Abstract

In optimization of thermodynamic cycles, it is appropriate for the economic and environmental aspects to be considered simultaneously. The sum of the fuel and investment cost flowrates is known as thermoeconomic objective function. A new objective function, known as a thermoenvironomic objective function, is obtained by integrating the environmental impacts, which should be defined and expressed in terms of cost, and thermoeconomic objective function. The objective of this paper is to study the effect of air preheater (APH) in the thermodynamic cycles by considering environmental impacts. In order to perform this, four simple thermodynamic cycles are selected and economic and environmental aspects are optimized. All considered thermodynamic cycles produce 30 MW of electricity and two of them, which are cogeneration systems, produce 18 kg/s of saturated steam at 20 bar, too. For optimization of these cycles, a code has been developed in MATLAB based on the real coding and optimal solutions have been obtained. The results show that the existence of APH increases exergetic efficiency of the cycles and the environmental impacts cost flowrate but decreases the total cost flowrate. Also, in the cycles without APH, the optimum values of decision variables corresponding to thermoeconomic and thermoenvironomic objective functions do not change considerably, while in the cycles with APH, they change noticeably.

Thermoenvironomic evaluation of simple, intercooled, STIG, and ISTIG cycles

“…For the unburned air‐fuel‐steam mixture, the temperature of the reactant air is equal to the compressor outlet temperature and fuel temperature is assumed to be equal to the ambient temperature. The combustion is assumed to take place at stationary state and adiabatic. Combustion chamber is assumed to be a well‐stirred reactor (WSR) and primary zone residence time is assumed to be 0.002 seconds Intercooling allows for a higher turbine inlet temperature because turbine blades are cooled with the air bled from the high‐pressure compressor.…”

“…Besides, they offer 6% higher availability and the possibility of remote operation without operators in continuous attendance and water requirements are less by one third . Because of these important advantages, optimal emissions and performance of STIGs are being studied by many authors . However, this modification requires constant supply of purified water and addition of a heat recovery steam generator.…”

“…Because of the uncertainties relating to thermodynamic comparison among different energy systems, the decision for on which option to give more emphasis should be made on grounds other than thermodynamic analysis alone. Therefore, many authors worked on thermoeconomics and thermoenvironomic optimization of gas turbine systems …”

Microturbine Design Point Evaluation and Optimization Considering Pollutant Emissions and Thermoeconomic Approach

“…An initial economic analysis would be helpful in making decisions to know if the project is viable, as well as to estimate the payback [15]. Several authors have analyzed the thermoeconomic calculations for different cycle configurations and perspectives [16][17][18][19][20][21]. For microturbines, little work was done in this sense due to recent developments, but the studies can be modified for microturbines.…”

“…(19)(20)(21). A, α, β, λ, a i , b i , and c i are constants (different sets of constants are used for different ranges of θ and φ due to the fact that the fuel-air ratio changes for each design point).…”