See also F.A.Q. at very interesting, informative site www.atmoswater.com
1. How do I compare the effectiveness of competing methods of obtaining water from the air?
Comparisons are possible if the equipment provider has stated water production capacity and energy input of their device at the standard conditions of 26.7 degrees C (80 degrees F) and 60% relative humidity. These are the standard conditions used by the dehumidification industry. The reference publication is AHAM DH-1-2008, Dehumidifiers, by the Association of Home Appliance Manufacturers.
2. Would the quality and quantity of water produced from air change depending on air quality (pollution index)?
Water quality is affected by air quality. For example, while operating a water-from-air machine in a region of eastern Canada, where electricity is produced by coal-fired plants, water quality tests revealed a trace of strontium in the product water of the machine. Although we did not test the air, we surmised the ambient air contained traces of strontium from combustion of coal. Strontium was not detected in product water while testing several machines in western Canada where electricity is from hydro-electric sources. Volatile organic compounds (VOCs) in the entering air can also pass through the system into the product water unless one or more VOC filters are added to the water flow path. Particulates in the ambient air can be removed by air filters before the air enters the water-from-air processing system. Sediment filters can be inserted into the water flow path to remove fine particulates not removed by the air filter. Before starting long-term use of water-from-air product water at a site, it is wise to have a sample of the product water tested by a reputable laboratory to ensure the water quality meets national or World Health Organization water quality guidelines. Tests should be scheduled annually to verify that water quality remains acceptable.
3. Would the quantity of water produced vary on a day to day basis?
Yes, water production rate depends on the water vapour density (“absolute humidity”) of the ambient air. The water vapour density changes according to weather conditions related to characteristics of the air masses passing through the region in which the water-from-air machine is located. Day-to-day variability is minor usually but month-to-month and seasonal variability can be substantial, especially in temperate climates.
4. How much energy is used to produce a liter of water in optimal conditions?
First let us say that optimal conditions = standard test conditions for dehumidifiers which is 26.7 C dry bulb air temperature, relative humidity 60%, and air pressure at one atmosphere. Under these test conditions, I have found both through modeling and real world measurement experience that 20 L/day machines consume 0.68 kWh per litre of water produced. Larger machines, typically rated at 2500 L/day consume 0.4 kWh per litre of product water. This is because the larger machines are more efficient at using the atmosphere as a heat sink. It is interesting to note that in natural systems, the energy consumed to change the phase of water from gas to liquid (enthalpy of vaporization, formery called ‘latent heat’) is 0.681 kWh per litre.
5. Do minerals need to be added to water with a low mineral content such as drinking-water-from-air?
Two credible organizations answered differently; the Water Quality Association (WQA) said ‘no’ while the World Health Organization (WHO) said ‘yes’.
WQA statement: “No. The human body gains the minerals necessary to good health primarily through eating foods, not through drinking water. The body may absorb or use the minerals in water but, in most cases, the amount would not be significant. In order for a person to obtain sufficient minerals from water, it would be necessary to drink many gallons daily. In general, neither a water with a high mineral content, nor a fully softened water, could be considered a significant source of minerals. In contrast, one glass of milk provides the mineral equivalent of multiple gallons of water from ordinary wells.
Note: Certain trace elements, such as fluoride, iodine, etc., may be obtained from water.” (from Water Quality Association, International Headquarters and Laboratory, Lisle, Illinois, USA)
WHO assessment: WHO—Calcium and magnesium in drinking-water
6. Has the worldwide use of water generators any effect on the quality of the ambient air? Will the air for instance become dryer as a result of using this technology on a large scale?