Water Extraction from Air: A Proposal for a New Indicator to Compare Air Water Generators Efficiency

Abstract

Water extraction from air, based on reverse cycle systems, is becoming a technology more and more diffused and various models of air to water generators (AWG) are now available, all claiming the best efficiency. To date, there is not a standard indicator stating energy efficiency for AWGs, neither in the literature nor in technical practice. The only evaluation parameter, that can be found is a sort of specific energy consumption (SEC) without any clear indications about the involved calculation terms, definition of hypotheses, or environmental conditions. The current work is a first proposal of an indicator to standardise the AWG efficiency evaluation. The indicator is called WET (Water Energy Transformation); it states water production as a useful effect of an AWG machine and calculates its energy performance with an approach similar to COP (Coefficient of Performance) and EER (Energy Efficiency Ratio) evaluation. The indicator is meant to be a normalised tool that permits comparing different AWG machines, but it is also the first part of a wider study, currently under development that is oriented to obtain a global index formulation that combines WET itself, EER and COP, and it is intended for a comprehensive evaluation of all the useful effects of a reverse cycle in integrated machines, in compliance with the current efficiency evaluation approach. The current paper presents the WET equation, with a discussion about involved terms, a set of normalised calculation conditions and some application examples, including a comparison with SEC.

A Recent and Systematic Review on Water Extraction from the Atmosphere for Arid Zones

“…Water extraction from air via reverse-cycle systems is becoming increasingly popular, and a variety of air-to-water generators (AWGs) are now available, all of which claim to be the most efficient [12]. The atmospheric water generator (AWG) is a possible solution for water scarcity since it converts water vapor to liquid water [13].…”

“…It includes two 2 L water tanks that are completely distinct from one another, and schedules can be applied to create water for each container at a specific time. The device is 35 cm in height, 25 cm in length, and 14 cm in width [12]. The method of water extraction from air is the same for all techniques, whether reverse cycle or not, and it involves driving the condensation of the air vapor content.…”

“…It includes two 2 L water tanks that are completely distinct from one another, and schedules can be applied to create water for each container at a specific time. The device is 35 cm in height, 25 cm in length, and 14 cm in width [12]. Condensation is the primary method by which the AWG converts water vapor to liquid water.…”

Air to Water Generator Integrated Systems: The Proposal of a Global Evaluation Index—GEI Formulation and Application Examples

“…For AWG machines, the authors have proposed a dedicated indicator, water energy transformation (WET) [18], which provides a metric for energy efficiency related to the specific useful effect of an AWG system: the water production. There are basically two scopes of WET:…”

“…Due to the novelty of the technology, presently, as underlined in [18], there is no index that is meaningful and able to give, in a compact and intuitive way, an indication on the efficiency of an integrated AWG machine, thus permitting a fast comparison with other plants, integrated or otherwise. Nowadays, for integrated AWG machines, the only way to carry out such a comparison is to use an analytic energy calculation of each individual useful effect provided by each system, such as heating, cooling, water extraction, etc.…”