Multi-generation energy system based on geothermal source to produce power, cooling, heating, and fresh water: Exergoeconomic analysis and optimum selection by LINMAP method

Abstract

The current study deals with thermodynamic modeling and multi-objective optimization of a new multi-generation energy system using geothermal as the primary energy source. The proposed system includes a Kalina cycle, a refrigeration unit, thermoelectric module, steam turbine, and heating unit. The new aspects of the proposed system are using the thermoelectric system to low temperature heat recovery and using the benefit of the multi-product. The system exergy analysis shows that the reverse osmosis desalination unit with 449.1 kW has the highest exergy destruction rate in the system. Additionally, three components i.e., reverse osmosis unit, heating system, and steam turbine are responsible for 82.8% of exergy destruction of the system. Exergo-economic analysis revealed that the turbine and the thermoelectric module have the highest cost rates of 12.51 US$/h and 3.62 US$/h respectively. It also concludes that the sum of the cost rate of component and associated exergy destruction cost rate, a significant exergo-economic parameter, for the turbine and reverse osmosis unit are the highest values. Parametric analysis of the proposed system for geothermal source pressure, steam turbine backpressure, Kalina turbine backpressure, and ammonia mass fraction of basic solutions are carried out. The unit cost of product and exergy efficiency are objective functions for optimization. Multi-criteria optimization indicates that using the Linear Programming Technique for Multidimensional Analysis of Preference (LINMAP) method based on suggested design variables, can reduce the unit cost of the product to 0.107 US$/kWh, and the exergy efficiency can be increased up to 15.86%.