Testing and Evaluating Performance of Atmospheric Water Generation (AWG) Systems in the UAE Climatic Conditions

Abstract

Scarcity in fresh surface water resources combined with over-exploitation of groundwater reserves across the United Arab Emirates (UAE) has increased the reliance on seawater desalination to meet the demand for potable water. The prevalence of high humidity and temperatures within this region, however, offers unprecedented potential for atmospheric water generation (AWG) to complement classical desalination technologies. The current use of most AWG production technologies is currently restricted to emergency response or isolated locations, where other water production/distribution techniques are out of order or impractical. This thesis presents an analysis of various scalable Atmospheric Water Generation (AWG) techniques including direct cooling of air using Vapour Compression Refrigeration Systems (VCRS), Air conditioner condensate recovery and fog harvesting. Three commercial VCRS were evaluated in both indoor and outdoor environmental operating conditions along with a 7.87 m3.s-1 fresh air handling unit and their performance were correlated to the relative humidity and temperature of the incoming air as well as airborne particulate matter content. The results show that machine A (EW 30) consumes an average of 1.15 kWh.L-1 of water, while machine B (Genny outdoor) consumes an average of 0.71 kWh.L-1 and machine C (Genny indoor) consumes an average of 0.8 kWh.L-1. An average of 90 L.h-1 was recovered from the AC condensates with a daily average of 2000 L.day-1. Additionally, a Neural network model was developed in Python using Keras API to predict the water production based on relative humidity and temperature and the model reports the root mean square error value of <15%. Due to a high number of intense fog events in the UAE, fog harvesting is seen as a potential source of freshwater supply. The study investigates the performance assessment of fog harvesting for the climatic condition of Abu Dhabi, UAE was conducted. Two different designs of fog collector i.e., horizontal, and vertical collectors with a mesh area of 1 m2 along with different shade coefficients of 40%, 50% and 60% were installed at the Masdar Institute Solar Platform of Khalifa University and tested from January 2022 to March 2022. Vertical fog collectors performed better than the horizontal one with a maximum water production of 80 mL.m-2.day-1 while the 50% shade coefficient was more efficient among the horizontal design collecting 5% more water than the 60% shade coefficient and 30% more water than the 40% shade coefficient. Additionally, a lab scale experiment was conducted to determine the effect of shade coefficients on the water production for high density poly(ethylene) mesh which revealed that 50% shade coefficient collects 34% more water than 60% shade coefficient and 28% more water than 40% shade coefficient. A study to investigate the optimum number of layers to harvest fog is also presented which reports that increasing the number of layers above two does not have any significant impact on the water production. The economic analysis to install and commission the fog collector is also presented. This thesis demonstrates the potential of AWG as promising solutions to increase water security across the UAE by offering an alternative solution to challenges arising from desalination technologies and brine management.

Date of Award	Dec 2022
Original language	American English
Supervisor	Nicolas Calvet (Supervisor)