Exergy analysis and parametric optimization of three power and fresh water cogeneration systems using refrigeration chillers

• Published in: Energy (Oxford) Vol. 59; pp. 340 - 355
• Main Authors: Janghorban Esfahani, I., Yoo, C.K.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.09.2013; Elsevier
• Subjects: absorption; air; air temperature; algorithms; Applied sciences; Cogeneration; cogeneration systems; desalination; Drinking water and swimming-pool water. Desalination; Energy; energy efficiency; Energy. Thermal use of fuels; Exact sciences and technology; Exergy; freshwater; GT (gas turbine); heat; Installations for energy generation and conversion: thermal and electrical energy; lithium; Optimization; Pollution; power plants; refrigeration; reverse osmosis; RO (reverse osmosis); seawater; Thermal power plants; Water treatment and pollution; RO (reverse osmosis); Exergy; Cogeneration; GT (gas turbine); Optimization; Membrane separation; Gas turbine power plants; Electric power plant; Chiller; Exergy analysis; Thermal power plant; Desalination; Reverse osmosis; Electric power production
• ISSN: 0360-5442
• DOI: 10.1016/j.energy.2013.07.040

Three power and fresh water cogeneration systems that combine a GT (gas turbine) power plant and a RO (reverse osmosis) desalination system were compared based on the exergy viewpoint. In the first system, the GT and RO systems were coupled mechanically to form a base system. In the second and third systems, a VCR (vapor-compression refrigeration) cycle and a single-effect ACWater–LiBr (water/lithium bromide absorption chiller) were used, respectively, to cool the compressor inlet air and preheat the RO intake seawater via waste heat recovery in the VCR condenser and ACWater–LiBr absorber. A parametric analysis-based exergy was conducted to evaluate the effects of the key thermodynamic parameters including the compressor inlet air temperature and the fuel-mass flow rate on the system exergy efficiency. Parameter optimization was achieved using a GA (genetic algorithm) to reach the maximum exergy efficiency, where the thermodynamic improvement potentials of the systems were identified. The optimum values of performance for the three cogeneration systems were compared under the same conditions. The results showed that the cogeneration system with the AC is the best system among the three systems, since it can increase exergy and energy efficiencies as well as net power generation by 3.79%, 4.21%, and 38%, respectively, compared to the base system. •Development of a thermodynamic model of power and fresh water cogeneration systems.•Model determines the thermodynamic properties, energy and exergy efficiencies, and net power generation.•Parametric analysis of the cogeneration systems to investigate the effects of decision variables on the system exergy efficiency.•Optimization using a GA (genetic algorithm) to maximize system exergy efficiency.•Exergy analysis of the cogeneration systems to guide the thermodynamic improvement.