Performance analysis of applying waste heat and moisture utilization in a highly efficient hybrid atmospheric water harvester

Abstract

Atmospheric water harvesting (AWH) can supplement freshwater in regions far from natural water reserves, and hybridizing different AWH technologies is known to increase the water generation rate. This research proposes an improved hybrid technology where the waste heat and unrecovered water from the vapor compression cycle-based AWH are recycled into a salt solution circuit-based AWH. Doing so eliminates the significant energy input for the second AWH and greatly minimizes the specific energy consumption. A system is designed to achieve this concept, which is analyzed via a comprehensive simulation that couples the thermodynamic models of the vapor compression cycle, humid air, and custom-designed salt solution circuit. The influences of ambient relative humidity, mass flow rates of humid air and the salt solution, etc., are conducted to find the optimal working conditions. Results demonstrate that, under an ambient relative humidity and temperature of 50% and 30℃, respectively, the proposed method can reduce the specific energy consumption to 315 Wh/kg, which equates to a 34.4% energy-saving rate over the basic vapor compression cycle based AWH. This is achieved by lowering the airflow and salt solution flow rates to 0.1 kg/s and 0.03 kg/s, respectively, while using a 1000 W compressor.