Exergoeconomic and environmental analyses of a novel multi-generation system including five subsystems for efficient waste heat recovery of a regenerative gas turbine cycle with hybridization of solar power tower and biomass gasifier

Abstract

This study aims to recover the waste heat from a previously introduced regenerative gas turbine cycle (GTC) when it is driven by a hybrid heat source composed of solar power tower (SPT) and biomass gasification. The system consists of electricity, cooling, heating, and hydrogen production subsystems. Therefore, the system is converted into a novel multi-generation system which is examined through energy, exergy, exergoeconomic, and environmental analyses. In the proposed system, to recover the waste energy of a topping GTC, a steam Rankine cycle (SRC) by employing a thermoelectric generator (TEG) instead of a conventional condenser, a domestic hot water heat exchanger (DHWHX), and an LiCl-H2O absorption refrigeration system (ARS) are utilized. The power recovered by the TEG is employed to produce hydrogen by a proton exchange membrane (PEM) electrolyzer. In the base case, the proposed system with the multi-generation exergy efficiency of 43.11%, can produce 98.2 MW of electricity which 24.7 MW of this production is owing to the waste heat recovery of GTC in SRC. Heating, cooling, and hydrogen production rates are 13 MW, 10.5 MW, and 4.1 kg/h, respectively. Due to the waste heat recovery of GTC, total exergy efficiency is increased by 9.04 percentage points. The total cost rate of the proposed system is 7799 $/h, and the unit cost of multi-generation is 8.26 $/GJ. Although the increase of direct normal irradiance (DNI) brings about a slight drop in the thermodynamic performance of the system, it improves the performance of the system from economic and environmental standpoints. By increasing the number of mirrors, which induces the reduction of fuel consumption and improvement of the environmental performance of the system, it is accompanied by weakening the performance of the system from thermodynamic and economic perspectives. By raising the pressure ratio of the GTC compressor, the heating production rate declines and the performance of the system decreases from economic and environmental aspects, while the net power output and multi-generation exergy efficiency have their maximum values at pressure ratios of 14.6 and 11.2, respectively. The only positive effect of increasing the pinch temperature difference of heat recovery steam generator (HRSG) is that it can significantly increase the heating production rate.