Abstract
A comparative exergoeconomic analysis is reported for waste heat recovery from a gas turbine-modular helium reactor (GT-MHR) using various configurations of organic Rankine cycles (ORCs) for generating electricity. The ORC configurations studied are: a simple organic Rankine cycle (SORC), an ORC with an internal heat exchanger (HORC) and a regenerative organic Rankine cycle (RORC). Exergoeconomic analyses are performed with the specific exergy costing (SPECO) method. First, energy and exergy analyses are applied to the combined cycles. Then, a cost-balance, as well as auxiliary equations are developed for the components to determine the exergoeconomic parameters for the combined cycles and their components. The three combined cycles are compared considering the same operating conditions for the GT-MHR cycle, and a parametric study is done to reveal the effects on the exergoeconomic performance of the combined cycles of various significant parameters, e.g., turbine inlet and evaporator temperatures and compressor pressure ratio. The results show that the GT-MHR/RORC has the lowest unit cost of electricity generated by the ORC turbine. This value is highest for the GT-MHR/HORC. Furthermore, the GT-MHR/RORC has the highest and the GT-MHR/HORC has the lowest exergy destruction cost rate.
Highlights
The value of the cost rate of power produced by the organic Rankine cycles (ORCs) turbine is determined to be $0.458/s, $0.461/s and $0.449/s for gas turbine-modular helium reactor (GT-modular helium reactors (MHRs))/simple organic Rankine cycle (SORC), GT-MHR/HORC and GT-MHR/regenerative organic Rankine cycle (RORC), respectively
The important exergoeconomic parameters are: the unit cost of electricity produced by the ORC turbine, cW,T,ORC, and the total exergy destruction cost rate, ĊD,total
It should be noted that an increase in turbine inlet temperature results in a decrease of the total exergy destruction cost rate, it causes an increase in the unit cost of electricity produced by the ORC turbine
Summary
A large amount of low-grade heat is rejected to a heat sink in this process [4] This is a potentially advantageous energy source for organic Rankine cycles for electrical power generation [5]. One of the interesting features of working fluids used in ORCs (compared to water in the Rankine cycle) is their relatively low enthalpy drop through the expander, which reduces gap losses and, in turn, increases the turbine adiabatic efficiency. In this system, which has a capacity of 297.7 MW, the helium is first heated in the reactor and expanded in the turbine to generate electrical power.
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