Experimental comparison and 6E analyses of double-ended evacuated tube collector based atmospheric water harvesting with and without PCM

Abstract

Globally, there is scarcity of fresh water resources, and existing water harvesting systems face various limitations, including the inability to operate at night, requiring high desorption temperature, and yielding limited amount of water. To tackle these challenges, a novel atmospheric water harvesting system is developed and compared experimentally with and without the use of phase change material (PCM). To generate hot air, the system consists of a 4.86 m² double-ended evacuated tube collector solar air heater and integrates an independent air-cooled condenser for vapor condensation. The system's performance is evaluated through 6E analyses of energy, exergy, environmental, economic, exergo-economic, and enviro-economic factors using silica gel and molecular sieve desiccants. The PCM-encapsulated system with silica gel reports peak thermal, overall and exergy efficiency of 30.06 %, 9.71 %, and 7.98 %, respectively, with maximum fresh water yield of 4.25 L/day at a cost of 0.11 $/L. Whereas, the system without PCM outperforms with molecular sieve having same parameters of 18.27 %, 10.21 %, and 2.84 %, respectively, with maximum fresh water yield of 4.40 L/day at a cost of 0.092 $/L. The PCM-encapsulated system using silica gel is eco-friendly by mitigating 37.31 tons of $CO₂$ at a sustainability index of 1.09, while the system using molecular sieve without PCM is eco-friendly by mitigating 34.23 tons of $CO₂$ at a sustainability index of 1.03. Further, the harvested water from both the designed systems reports to be safe for domestic and commercial use.