Exergoeconomic and environmental analyses of a novel trigeneration system based on combined gas turbine-air bottoming cycle with hybridization of solar power tower and natural gas combustion

Abstract

This study aims to recover the waste heat from a previously introduced combined gas turbine cycle (GTC) and air bottoming cycle (ABC) when it is driven by a hybrid heat source composed of natural gas combustion and solar power tower (SPT). The waste heat of the GTC is utilized as the heat source for a heat recovery steam generator (HRSG) and an LiBr-H2O absorption refrigeration system (ARS) to respectively produce heating and cooling. An organic Rankine cycle (ORC) is also driven by the waste heat of ABC. Therefore, one can have a trigeneration system which is assessed via energy, exergy, exergoeconomic, and environmental analyses. In the base case, employing the three subsystems causes a 8.9% improvement in net power output. Also, they contribute to 13.39 and 4.43 percent point improvement in energy and exergy efficiencies of the whole system, respectively. However, a 7.26% increase in the total cost rate of the system is evident owing to the addition of the subsystems. Moreover, the rate of power, heating, and cooling production was obtained as 36.9, 10.6, and 8.8 MW, respectively. The investigation of the system revealed that adding the subsystems to the topping cycle conduces to a reduction in the payback period and environmental index of the total system. The parametric analysis shows that an increase in direct normal irradiance (DNI) and compressor pressure ratio (CPR) of the GTC as well as a decrease in gas turbine inlet temperature (GTIT) leads to a drop in the thermodynamic performance of the system as well as an improvement in the economic and environmental performances of the system. Moreover, an increase in the CPR of ABC and a reduction in Air heat exchanger (AHX) effectiveness, lead to a drop in all thermodynamic parameters of the system, except for the heating production which experiences an enhancement. This is while the economic performance of the system improves as a result of mentioned alterations.