Efficient waste heat recovery of a hybrid solar-biogas-fueled gas turbine cycle for poly-generation purpose: 4E analysis, parametric study, and multi-objective optimization

Abstract

In the present theoretical study, a steam Rankine cycle (SRC) and a modified organic flash cycle (MOFC) are used as bottoming systems for a gas turbine cycle (GTC). Then, the waste energy of the compression stage of the GTC is recuperated by a hot water unit, and the waste energy of the SRC and MOFC is recovered in a single effect LiCl-H2O absorption chiller and a thermoelectric generator, correspondingly. Furthermore, the power produced in the SRC and MOFC is transmitted to a proton exchange membrane electrolyzer and a reverse osmosis desalination unit to produce hydrogen and freshwater. Thus, the system is converted into a ploy-generation layout. In the parametric study section, the effects of changes in the pressure ratio of the GTC, inlet temperature of the solar power tower, number of heliostat mirrors, methane content of biogas, inlet temperature of the gas turbine, and direct normal irradiance on the energy, exergy, exergy-economic, and environmental output parameters are investigated. The results show that solar power tower is the most influential component in the exergy destruction and cost rates. Furthermore, the exergy efficiency, total cost rate, the unit cost of products, and payback period are obtained as 24.34 %, 6390 $/h, 20.17 $/GJ, and 0.687 years in the base case. Considering exergy efficiency and total cost rate as the objective functions, these two parameters improved by 14.87 % and 11.01 % in the optimum case, respectively.