Investigating potential benefits of a salinity gradient solar pond for ejector refrigeration cycle coupled with a thermoelectric generator

Abstract

Extraction of thermal heat from a salinity-gradient solar pond (SGSP) as a way of accumulating solar energy, stockpiling and taking merit of it for medium and low temperature demands is presented as an interesting topic in recent decades. This reliable supply of heat can be used for low-temperature refrigeration systems to yield cooling load for residential applications. For this purpose, theoretical investigation of ejector refrigeration cycle (ERC) driven by a SGSP is carried out to produce cooling output. Also, thermoelectric generator (TEG) is used as a potential device replacing condenser of the ERC for the sake of bolstering performance of the fundamental system by producing power, using heat from SGSP. To express viscosity effect of refrigerant through different components of ejector, available numerical correlations are used and it is demonstrated that this deliberation highly increases the accuracy of ejector mathematical modeling. An extensive thermodynamic evaluation on the basis of the mass-, energy-, and exergy-based balance relations for disparate constituents of the introduced system is executed and the outcomes are corroborated with those of experiential approaches. Moreover, performance of the integrated system is optimized by maximizing energy efficiency as well as exergy efficiency for an optimal solar pond. At the optimum mode, the outcomes of modeling portrayed that the introduced system can culminate in furnishing cooling capacity of 9.216 kW and net electricity of 1.026 kW, respectively, at lower convective zone (LCZ) temperature of 359.7K, LCZ's thickness of 1.003m, non-convective zone of 1.339m, upper convective zone of 0.102m, and solar pond area of 189,476m2. Under this optimum condition, the energy and exergy efficiencies are evaluated around 28.26% and 29.95%, respectively, using R245fa as working fluid in the ERC. In the optimal scenario, the ERC should be designed with primary pressure of 0.49 MPa, secondary pressure of 0.098 MPa, mass entrainment ratio of 0.3046, nozzle efficiency of 96.77%, mixer efficiency of 95.52%, and diffuser efficiency of 76.7%.