Exergoeconomic analysis and optimization of basic, dual-pressure and dual-fluid ORCs and Kalina geothermal power plants: A comparative study

Abstract

In present work, the basic, dual-pressure and dual-fluid ORCs and Kalina cycle for power generation from the geothermal fluid reservoir are compared from energy, exergy and exergoeconomic viewpoints. To do so, first thermodynamic models are applied to the considered cycles; then by developing cost flow rate balance and auxiliary equations using SPECO method for all components, the cost flow rate and unit cost of exergy for each stream are calculated. The results show that the turbine in basic and Kalina cycles and low pressure turbine in dual-pressure and dual-fluid ORCs have the maximum value of sum of total cost rate associated with exergy destruction and total capital investment cost rate. Thus, more attention should be paid for these components from the exergoeconomic viewpoint. The cycles are optimized to obtain maximum produced electrical power in the cycles as well as minimum unit cost of produced power. The optimization results show that among the considered cycles, dual-pressure ORC has the maximum value of produced electrical power. This is 15.22%, 35.09% and 43.48% more than the corresponding values for the basic ORC, dual-fluid ORC and Kalina cycle, respectively in optimal condition. Also Kalina cycle has the minimum value of unit cost of power produced and its value in optimum state is 26.23%%, 52.09% and 66.74% less than the corresponding values for the basic ORC, dual-pressure ORC and dual-fluid ORC, respectively in optimal condition. Finally a parametric study is carried out to assess the effects on thermodynamic and exergoeconomic parameters of the considered cycles of operating pressures and ammonia mass concentration.