Performance enhancement and parametric optimization of a sky radiative and thermoelectric hybrid cooling system for water harvesting from humid air

Abstract

The aim of this study is to deepen into the study and analysis of energetic performance of a novel RSC-TEC hybrid cooling system for water harvesting by combining thermoelectric and radiative sky cooling mechanisms. The main contents of this study are to propose the thermodynamic model of the novel hybrid system considering main losses and steady-state assumption, solve the operating temperatures of the thermoelectric cooler by energy balance equations, discuss the influences of multiple system variables including air flow rate, electric current of the thermoelectric cooler, ambient relative humidity, and ambient temperature on effectiveness and water production rate, and, evaluate and compare the performances of the whole system and the thermoelectric cooler. The main novelties are to provide the parametric optimum selection criteria of some key parameters of the overall system operating at optimum states. Results show that the maximum effectiveness and water production rate of the hybrid system can reach 1.93×10- 6 kg J−1 (amount to 6.95×103 ml of water by consuming 1 kWh of electrical energy) and 1.51×10- 5 kg s−1 (amount to 54.4 ml of water within 1 h) at 0.75 relative humidity and the ambient temperature of 298 K. In addition, the system is capable of producing about 140 ml of water within 1 h from the air with high relative humidity, which is more efficient than other different existing air water generators. The optimized effectiveness (coefficient of performance) of the hybrid system is much better than that of a separate (subsystem) thermoelectric cooler operating at the same ambient condition. The results obtained reveal the advantages of the present hybrid system. Complementary perspectives on compromise performance regimes are also displayed from Pareto front yielded from numerical multi-parametric and multi-objective methods.