Thermo-economic evaluation of a combined Kalina cycle and humidification-dehumidification (HDH) desalination system integrated with thermoelectric generator and solar pond

Abstract

This study aims at introducing a new layout for cogeneration of power and distilled water using thermal heat stored at the lower convective zone (LCZ) of a salinity-gradient solar pond (SGSP). The proposed system consists of a Kalina cycle (KC), a humidification-dehumidification (HDH) unit, and two thermoelectric generators (TEGs). The feasibility of the devised system at the base and optimal modes of operation under the steady-state assumption is carried out, using thermoeconomic and the rmodynamic tools. Later, a parametric study is carried out and the effects of important design factors on the system performance and cost metrics were investigated. The results of multi-objective optimization revealed that the energy utilization factor (EUF), exergy efficiency, and total unit cost of the product (TUCP) can be improved by 14.09%, 5.5%, and 27.93%, respectively, in comparison with the base case. The optimum EUF, exergy efficiency, and TUCP were achieved at 0.756, 27.7%, and 30.54 $/GJ, respectively, when the proposed power/desalination system was designed under the following design parameters: solar pond area of 15326 m2, LCZ thickness of 1.65 m, NCZ thickness of 1.35 m, UCZ thickness of 0.35 m, LCZ temperature of 370 K, the figure of merit of 2.45, desalination flow ratio of 2.45, the turbine inlet pressure of 2500 bar, the pump pressure ratio of 3, and ammonia concentration of 86%. The results of the case study showed that between 20 March and 20 April the system produces the minimum rate of freshwater, which is 0.152 m3/h. On the contrary, the maximum amount of distilled water can be obtained between 21 June and 21 July. Moreover, from 21 May to 21 August is the best time to run the system to produce simultaneous distilled water and electricity.