Water-from-air technologies are attracting serious attention as shown by a recent editorial in the journal Nature Water. Highlights from the editorial include:

• Materials science is fostering advances;
  
• Globally, there are relatively few commercial installations;
  
• The energy cost of water-from-air remains an obstacle;
  
• Desiccant technologies coupled with renewable energy sources are likely to be a versatile path forward;
  
• Relevant markets are remote arid regions with little or no conventional water supplies;
  
• Energy efficiency depends on a deep understanding of water properties; and
  
• Although water-from-air has "unique advantages" being "accessible anywhere" and readily used with renewable energy its "role in providing freshwater is still open for discussion". 

[Text excerpted and adapted from Technical Bulletin No. 5 (revised 2023)—Environmental impact of widespread use of drinking-water-from-air systems issued by Canadian Dew Technologies Inc.

This blog post supersedes two earlier blog posts on the same topic (My answers to questions asked in Oct. 20, 2020 Webinar: Introduction to Atmospheric Water and Impact on the atmospheric water reservoir from using water-from-air systems: an update) The human population keeps increasing and estimates have been refined of the atmospheric water reservoir volume.

Concern has been expressed by some potential users of WFA systems that widespread use in a region could decrease the water vapour content of the atmosphere. If this was the case, would regional weather and climate be affected?

Assessing Environmental Impact on the Atmospheric Water Reservoir
Earth’s estimated human population is now 8 billion, projected to increase to 10.4 billion in 2100 (https://population.un.org/dataportal/home) so the 1993 worst-case impact estimate was updated as follows in the next paragraph, incorporating a revised per capita water consumption value of 50 L/day as suggested by Gleick (1998) for domestic water requirements (drinking, kitchen, laundry, and bath). Revised water cycle information was from Abbott et al. (2019).

The atmosphere contains 12.9 × 10^12 m^3 of water or 0.001% of the Earth’s total water reservoir volume of 1.38 × 10^18 m^3. Water reservoirs include the atmosphere, ice and snow, biomass, surface water, underground water, and the oceans. Even if all 8 × 10^9 people on Earth used water from water vapour processors at the rate of 50 litres per day, they would consume only 0.003% of the available atmospheric water. In 2100, when population is expected to rise to 10.4 × 10^9, this worst-case impact would rise slightly to 0.004%.  

Water vapour, the gas phase of water, diffuses along pressure gradients to zones of lower water vapour pressure. If a lot of water vapour was condensed into liquid water in a specific region such as a city, water vapour from outside the region would flow into the region. No net loss of atmospheric water vapour would be observed in the city.

Water consumed for domestic water requirements does not exit from the water cycle. Within a day the water that is used or temporarily withheld from the water cycle would be returned to the environment to evaporate into atmospheric water vapour.

​Quantifying the Direct Environmental Impact of Dehumidifiers and Air-Conditioners on the Atmospheric Water Reservoir
An unintentional experiment has in fact already been running for the past 70 years. This experiment allows us to quantify the environmental impact to date of the human population processing atmospheric water vapour on a grand scale.

Since about 1950 the widespread use of dehumidifiers and air-conditioners across the globe has resulted already in vast volumes of condensate dripping from millions of machines. In fact, Wikipedia: Air Conditioning (https://en.wikipedia.org/wiki/Air_conditioning) stated, "According to the IEA [International Energy Agency], as of 2018, 1.6 billion air conditioning units were installed...." The same Wikipedia article said, "Innovations in the latter half of the 20th century allowed for much more ubiquitous air conditioner use. In 1945, Robert Sherman of Lynn, Massachusetts invented a portable, in-window air conditioner that cooled, heated, humidified, dehumidified, and filtered the air."

Has this experiment affected, in the long-term, the amount and geographical distribution of water vapour in the atmosphere? An analysis using data available from NOAA suggests not. Figure 1 shows the difference field of specific humidity resulting from subtracting the composite means (Jan to Dec) for the 10-year period 1948 to 1957 from the 20-year period 2013 to 2022. Surprisingly, several regions of increased specific humidity +1 to +2 g/kg are noticeable along Earth’s Tropical Belt. The increased water vapour content of the atmosphere is likely linked to global warming causing increased evaporation. Drying of about -2 to -3 g/kg is associated with the eastern Sahara and the Gobi deserts—more likely to be related to climate change than use of air-conditioning equipment in these sparsely populated areas. For most of Earth’s surface, specific humidity has been remarkably stable (+/-1 g/kg) over the past seven decades.

Precipitation Enhancement
On a well-defined land surface such as a tropical island, atmospheric water vapour processing systems would effectively increase annual precipitation. A viability study for a WaterProducer-Greenhouse™ (WPG) system on the tropical North Atlantic island of Grand Turk (with surface area 18 km^2 = 1800 ha = 18,000,000 m^2) illustrated this effect (Wahlgren, 2002). The proposed WPG system would produce water at a rate of 75,335 m^3 per year. This is equivalent to a rainfall depth of 75,335 m^3 / 18,000,000 m^2 = 0.00418 m = 4.18 mm. The average annual precipitation of Grand Turk is 604 mm. The WPG operation would augment this value by 4 mm (0.7% annually), an amount less than observed natural variability from year to year. The annual total precipitation in 2000, for example, was 704 mm (Wahlgren, 2002, 30).

Indirect Environmental Impacts
Using new technology such as atmospheric water vapour processing in drinking-water-from-air machines may have other impacts on Nature. These include:
• Possibility for more people to live in a region, thereby increasing the population density;
• Increased sewage and other waste (including material waste from machines which have reached the end of their operational life and are scrapped);
• Increased energy use (to operate the machines); and
• Increased material use (to build the machines).

Conclusion
The quantitative analyses outlined in this bulletin demonstrate that the direct environmental impact of widespread use of atmospheric water vapour processing technology can be considered negligible. In summary, scenarios involving the entire human population using processors of atmospheric water vapour are unlikely, so it is also unlikely that water-from-air technologies will cause a drier atmosphere in the context of the Earth’s water cycle and natural processes of water transport and distribution.

References
Abbott et al. (2019). Human domination of the global water cycle absent from depictions and perceptions. Nature Geoscience 12, 533–540, 10 June 2019.
Gleick, P. H. (1998) The World’s Water 1998–1999: The Biennial Report on Freshwater Resources. Island Press, Washington, DC.
van der Leeden, F., Troise, F. L., and Todd, D. K. (1990) The Water Encyclopedia, 2nd ed. Lewis Publishers Inc., Chelsea, Michigan.
Wahlgren R. V. 2002. Technical Feasibility Study—Grand Turk Solar Desalination Greenhouse for Water + Food™, 2nd ed. (revised September 2002). Report delivered to Batavia Greenhouse Builders Ltd. by Atmoswater Research, North Vancouver, BC, Canada.

Water News Europe published this article in July 2023 outlining the present state of the water-from-air industry. Several industry sources are referenced, including Roland Wahlgren, Atmoswater Research.

​Peer-reviewed articles, even about water resources, can be a dry read. But not so for the recently published Open Access article, Increasing freshwater supply to sustainably address global water security at scale. Let me share four excerpts from the paper to inspire and energize us in the water-from-air community. The excerpts show we do indeed have a crucial role in improving access to drinking water.

- "...reducing and managing [water] demand are proving inadequate as population and economic growth quickly absorb any capacity that is created through these measures."
- "Recycling and reuse of water...have limited scalability because they are fundamentally constrained by the available supply."
- "Effective solutions to increase the [fresh water] supply are at present limited, or they are practically non-existent since all resources are being exploited beyond sustainable capacity or rapidly dwindling due to climate change."
- "Desalination is not only energy intensive; it also creates concentrated brine and other byproducts that create significant environmental challenges with the cost of disposal."

The authors proceed to outline their proposal for a system for siting water vapor collection systems above the surface of the ocean and then transporting the vapor to condensation systems on the nearby shore. They discuss the water vapor resource, the insignificant impact of climate change on viability of their system, the negligible environmental impact, and the financial feasibility. The research trio also claim their ocean-based system will benefit from a higher moisture flux compared to land-based water-from-air installations.

The merits of the system outlined in the article remain to be validated but the important learnings from the article for those of us in the water-from-air industry are the quotations about the continuing inability of conventional water resources to provide global water security---thus giving incentive to our industry leadership to continue working diligently to prove the value of developing and commercializing water-from-air technologies.

Reference
Rahman, A., Kumar, P. & Dominguez, F. (2022). Increasing freshwater supply to sustainably address global water security at scale. Sci Rep 12, 20262 (2022). https://doi.org/10.1038/s41598-022-24314-2. This is an Open Access article.

Some water-from-air system suppliers have shown interest in deploying their systems in Jackson.

The city's water system is not functioning properly following recent rains and flooding. Even before these events the water system was unreliable according to NBC News.

Is Jackson a good location for water-from-air systems? The Water-from-Air Resource Chart for Jackson grades the atmospheric water resource month-by-month. The chart is available as a free download. The monthly average dewpoint is 3 to 4 degrees C during December to February. Because these temperatures are close to the freezing point of water, some atmospheric water generator (AWG) designs may experience constraints on their water-from-air production capacity during these three months. For the balance of the year AWGs in Jackson should operate satisfactorily. See the chart for more information.

​Here I refer again to statistics from UNICEF’s Water, Sanitation and Hygiene in Healthcare Facilities: Global Baseline Report 2019 which is found at:
https://data.unicef.org/resources/wash-in-health-care-facilities/?mc_cid=f5b26e1fed&mc_eid=1956e675a7)
The UNICEF report stated, “In 8 out of 55 countries with data available, more than half of health care facilities lacked handwashing facilities at points of care in 2016”. This is an urgent need that could be filled by appropriately designed AWGs.

Today's post presents data about healthcare facilities with no handwashing facilities (Table 7, below).

​The detailed statistical table from which the tables are derived is too large to reproduce in this blog series. The detailed table is available at https://washdata.org/data/downloads (select “World File” under “Health Care Facilities”). Water service data is given for the following regional groupings of healthcare facilities:

• National,
• Urban, and
• Rural.

Data is provided for the following four types of healthcare facilities:

• Hospital,
• Non-hospital,
• Government, and
• Non-government.

Using the original large table, which is a Microsoft Excel® spreadsheet, it is possible to explore the commercial potential for AWGs in some detail. For example, which countries have the highest proportion of hospitals with no water service or no hygiene service? Those hospitals would be expected to be receptive to an innovative water supply solution like AWGs.

This is the final post in this 7-part series about water-from-air market analyses based on the UN's Sustainable Development Goal 6 (Clean Water and Sanitation). Perhaps this series will inspire readers to initiate projects aligned with SDG 6. This alignment will create a demand for AWGs designed to address needs beyond household drinking water. AWGs are needed for household sanitation, basic water services in schools, handwashing in schools, basic water services in healthcare facilities, and healthcare handwashing facilities. Innovative business models are needed to allow water-from-air system suppliers to participate in achieving SDG 6 targets.  

Statistics from UNICEF’s Water, Sanitation and Hygiene in Healthcare Facilities: Global baseline report 2019
https://data.unicef.org/resources/wash-in-health-care-facilities/?mc_cid=f5b26e1fed&mc_eid=1956e675a7)
show the commercial potential for AWGs in the healthcare facility market in two market segments:

• Water services for healthcare facilities
• Handwashing facilities for healthcare facilities

The foreword to the report stated:
An estimated 896 million people use health care facilities with no 
water service and 1.5 billion use facilities with no 
sanitation service. It is likely that many more people 
are served by health care facilities lacking hand hygiene 
facilities and safe waste management.

Today's post presents data about healthcare facilities with no water service (Table 6, below).

Basic hygiene services in schools depends on clean water being available for handwashing. AWGs could be designed specifically for this application. Table 5 below shows the national statistics. The world file tables available at https://washdata.org/data/downloads also show urban and rural statistics so quite detailed market analyses are possible.

It is often said that children are our future. This truism may explain the special interest shown by WHO and UNICEF in compiling statistics about school drinking water services (Table 4, below) and school basic hygiene (Table 5, to be posted later in Part 5 of 7). There is commercial potential for AWGs designed for use in schools in drinking water and handwashing applications. Drinking water AWGs for schools and AWGs for handwashing by students are market segments rarely mentioned by academic researchers developing AWGs and by businesses offering AWG products. Welcome exceptions are the atmospheric drinking water fountain products by Hydrosphair and Skywell. The tables show the enormous potential for appropriately designed AWGs. These tables show the national statistics. The world file tables available at https://washdata.org/data/downloads also show urban and rural statistics so quite detailed market analyses can be done.

Countries, areas, or territories with school drinking water services less than 75% of school age population are listed here in Table 4.

​There are seventy-two countries, areas, or territories in which less than 75% of the population lives in households having safely managed sanitation (Table 3, below). Safely managed sanitation has these two properties: improved sanitation facility not shared with other households and excreta are disposed of in situ or transported and treated off-site.

Many countries in the drinking water list (Table in blog post 2 of 7) do not appear in the sanitation list (Table 3, below) because of gaps in the national sanitation data. The countries so affected do, however, have national statistics for “latrines and other”, “septic tanks”, and “sewer connections”. For the record, 16 countries were expected to be in both tables but were not (in order of lowest to highest national proportion of safely managed drinking water): Rwanda, Uganda, Afghanistan, Cambodia, Côte d’Ivoire, Pakistan, Congo, Tajikistan, Nicaragua, Guatemala, Wallis and Futuna Islands, Uzbekistan, Democratic People’s Republic of Korea, Kyrgyzstan, Albania, and Republic of Moldova.

Surprisingly, the list in the Sanitation Table below contains some countries that are in the High-income group as defined by their nominal values of Gross National Income (GNI) per capita in 2020‒2021 [>US$12,695; Atlas method— indicator of income developed by the World Bank; Wikipedia: List of countries and dependencies by GNI (nominal) per capita, USD]. These high-income group countries with relatively great household sanitation challenges are: Australia; China, Macao SAR; Croatia; Norway; Saudi Arabia; and Slovenia. Because of their relatively high per capita income status, these countries are good initial marketing targets for versions of AWGs designed to provide clean water for sanitation applications.

​In Table 1 (Blog post 1 of 7 in this series), the shortfall for safely managed drinking water is 2 billion people. The shortfall for safely managed sanitation is almost twice as many people, 3.6 billion. Why? To understand the commercial potential of AWGs and formulate marketing strategies it is crucial to know the reasons. In 2014, a blog post titled “Water and Sanitation for Health: Why is Progress Slow?” was published by Q. Wodon, Lead Economist, Education Sector, World Bank and C. T. Nkengne, Economist, Poverty Global Practice, World Bank Group
(https://blogs.worldbank.org/health/water-and-sanitation-health-why-progress-slow). Their main points help to answer why:

• “Several million people, many of them [children], die from diarrheal diseases every year. Many of these deaths can be attributed to unsafe water, poor sanitation and poor hygiene”;
• Supply factors are “at play” including “lack of infrastructure functionality”, “lack of local responsibility”, water scarcity;
• “[One] should not underestimate the role of culture, tradition, and behaviors”;
• “Adequate sanitation is also essential for health. Yet again, in many low-income countries, only a small minority of households has access to improved sanitation. Part of this may be due to a low priority assigned to sanitation in terms of public funding. But part of it is also due to cultural and traditional norms, as well as lack of income or time. Poor terrain or soil type and a lack of land to build latrines also play a role in some areas”;
• “Focus group participants were asked why they pay for cell phones but not for latrines. They responded that latrines have a much larger one-time cost, but also that having a cell phone is a sign of modernity and important for one’s status in communities. Clearly, more needs to be done to convince households of the importance of latrines, for example through sanitation marketing campaigns”;
• “Finally, in terms of health benefits, there is perhaps no more cost-effective intervention tha[n] the promotion of hand washing, but only a small minority of Uganda’s households (less than one in ten) has a facility to wash hands with both soap and water. Information campaigns are held, but, as a participant in focus groups noted, “many of the community members do not attend them, saying that these trainings are a waste of time”;
• “hand washing is viewed as a very strange practice to the local culture”; and
• “Uganda has invested over the years in safe water and sanitation. But the constraints faced by households and communities are complex. The qualitative work implemented in 14 districts suggests that solutions often must be context- and community-specific.”

​I have noted, over many years in the water-from-air field, that academic researchers and businesses are focused almost totally on providing potable water—sanitation gets mentioned rarely, if at all. But clean water is essential for personal hygiene for men, women, children, and infants—using polluted water or not having any water at all for sanitation applications has the potential for causing dreadful health problems. Designing versions of AWGs specifically for personal hygiene could be a competitive advantage that would also improve the quality of life for millions of people.

Households, schools, and healthcare facilities are essential markets to focus on according to the WHO/UNICEF Joint Monitoring Program for Water Supply, Sanitation and Hygiene (JMP). JMP is the data-holding entity monitoring progress towards the SDG 6 targets. Other markets exist but those mentioned are global priorities for which improving water supplies will improve the lives of millions of people by 2030. To position an AWG technology to help solve global water scarcity problems quickly and efficiently it is wise to adopt the priority markets outlined in the data tables by the experts involved with JMP ( Table downloads at: https://washdata.org/data/downloads#).

There are fifty countries, areas, or territories with data showing less than 75% of their population lives in households having safely managed drinking water (see Table 2 below). A safely managed water supply has all three of these properties: located on premises, available when needed and free from fecal and priority chemical contamination (WHO and UNICEF, 2017, p. 24). Households whose water supply lacks one or more of these properties are a commercial opportunity for AWGs. Examining the table at the national level reveals details about target markets. For example, in Uganda (seventh on the list, sorted by proportion of population using safely managed water supplies) only 17% of the population has water accessible on their premises. Despite this fact, water is available when needed for 73% of Ugandans. But, unfortunately, only 62% of people have access to water free from contamination. The statistics also show that only 23% of the improved water supply is piped—so decentralized water distribution solutions like AWGs are a good fit to the situation. The original full data tables, available from the WHO and UNICEF Joint Monitoring Program further organize the national data into its rural and urban components (https://washdata.org/data/downloads#). This allows AWG marketing strategy development to be quite efficient.

Reference
​WHO & UNICEF (2017). Progress on drinking water, sanitation and hygiene: 2017 update and SDG baselines. Geneva: World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF), 2017. Licence: CC BY-NC-SA 3.0 IGO.

The commercial potential of atmospheric water generators (AWGs) can be evaluated in the framework of the United Nations Sustainable Development Goals (SDGs). These global goals were set in 2015 by a unanimous vote in the UN General Assembly. The goals are to be met by 2030. The SDGs relevant to water resources make plain the urgent demand for specific products and services. They also state market segments and geographical regions that must be addressed to improve the quality of life for millions of people. In short, the SDG documents contain global market survey results, outlining concisely the big-picture problems that innovative products and services must help solve.

​As a reminder, and to put the water-related SDG in context, here is list of the seventeen SDGs (https://www.un.org/sustainabledevelopment/sustainable-development-goals/):
1. No Poverty
2. Zero Hunger
3. Good Health and Well-being
4. Quality Education
5. Gender Equality
6. Clean Water and Sanitation
7. Affordable and Clean Energy
8. Decent Work and Economic Growth
9. Industry, Innovation, and Infrastructure
10. Reduced Inequalities
11. Sustainable Cities and Communities
12. Responsible Consumption and Production
13. Climate Action
14. Life Below Water
15. Life on Land
16. Peace, Justice, and Strong Institutions
17. Partnerships for the Goals

Each goal has a list of targets.  Indicators measure progress towards achieving targets.
​
The SDG relevant to AWG design is Goal 6, Clean Water and Sanitation. The following Table 1 is my interpretation of how SDG 6 targets translate into insights about commercial potential for AWGs and the market segments to be addressed. These insights may influence design paths taken towards the final commercial versions of AWGs.

There is a lot to say about this topic, so I've prepared seven blog posts to be published as a series.

My goal is to remind readers of the scope of the water crisis. No single technology can hope to end the crisis. Solving water scarcity requires a variety of solutions applied thoughtfully region by region. Some powerful solutions are behavioral (and therefore essentially free of any cost in the long term). One example is reduction or elimination of mismanagement of surface water and groundwater. Another example is increased water conservation by individuals, businesses, and institutions. Some solutions are related to maintenance of water distribution infrastructure that should really be done anyway but require leadership and political willpower to include sufficient maintenance funds in budgets.
​
A variety of technological solutions are also likely to be needed. Water-from-air can be a valuable gap-filler in situations where conventional water supply or conventional sanitation solutions are difficult to apply or have failed. The SDG 6-related data tables in the following posts reflect these difficulties and failures. Clearly, proponents of water-from-air technologies have an enormous range of water scarcity problems to help solve.

The second blog post will look at national data for safely managed household drinking water.

California's Water Supply Strategy (19-page document; click on the image above to read it) was published in August 2022. The strategy includes:

• Storm water storage
• Recycling and reuse
• Efficiency of use and conservation
• Desalination
• Modernization of water systems
• Improving water management (data, forecasting, administration of water rights)
• Groundwater recharge expansion
• Reservoir expansions
• Dam rehabilitations
• Demand reduction
• Groundwater supply stabilization
• Improve flexibility of water transportation

The use of atmospheric water generators (AWGs) is not mentioned in the document. But, AWGs can be effective drinking water supply gap-fillers in site-specific situations. Examples include:

• off-grid residential or commercial applications,
• high quality water for beverage or food manufacturing,
• retrofitting water dispensers into buildings lacking sufficient plumbing infrastructure, and
• alternative to bottled water coolers in homes, offices, and factories.

Intriguingly, the Strategy document says, "Rising temperatures evaporate more water, but more of that water stays in the air." (page 1 of 16). AWG's can recover that sequestered water.

The knowledge-base for using atmospheric water generators in California includes:

• Product information from AWG suppliers, some based in California,
• Atlas of the Water-from-Air Resource for California,
• Water-from-Air Hourly Model Report for Watsonville, California, USA, and
• Water-from-Air Resource Charts: California.

I trust you are enjoying your visit to Atmoswater Research and are gaining some valuable knowledge about water-from-air topics. Since 1999 the Atmoswater Research website has endeavored to provide the water-from-air community with accurate scientific & technical information---with a lot being free to access. Although consulting contracts, sales of digital goods, and advertising revenue give us an income stream it is far from being predictable and steady. Maintaining and improving this site requires a certain amount of cash flow. Therefore, we have added a "tip jar" for those who would like to support us financially but do not have an immediate need for consulting services, digital goods, or an advertising spot. The tip jar is located on our home page, right-hand column (bottom; scroll down). Clicking the button below also opens the tip jar which is a secure page in the PayPal system. Thanks very much for your support!

-Roland Wahlgren 

PepsiCo mentioned AWGs in its recent call for proposals to improve water use efficiency. You may click on the image above to reach the Innoget website with the proposal call.

This interesting article by Global Water Intelligence (GWI) gives their view of the state of the water-from-air industry in July 2021. Drupps AB provided a link to the full article via their website. 

My previously published comments (Wahlgren, 2018, 51-53 and blog post of 29/10/2020) about the impact on the atmospheric water reservoir from using water-from-air systems need to be updated as follows because of human population growth.

The atmosphere contains 15.5 x 10^12 cubic metres of water or 0.001% of the Earth's total water reservoir volume of 1.46 x 10^18 cubic metres. Water reservoirs include the atmosphere, ice and snow, biomass, surface water, underground water, and the oceans. Even if all 7.9 x 10^9 people on Earth used water from water vapour processors at the rate of 50 litres per day, they would consume temporarily only 0.0025% of the available atmospheric water. In 2100, when population is expected to be 10.9  x 10^9, this worst case impact would rise slightly to 0.0035%. 

The most recent water cycle information I could find was from the AGU (1995). The per capita water consumption value of 50 L/day was suggested by Gleick (1998) for domestic water requirements (drinking, kitchen, laundry, and bath). Today's population estimate was from Worldometers. The year 2100 population estimate was from Wikipedia:Projections of population growth.

Water vapour, the gas phase of water, diffuses along water vapour pressure gradients to zones of lower water vapour pressure. If a lot of water vapour was condensed into liquid water in a specific region such as a city, for example, water vapour from outside the region would flow into the region. No net loss of atmospheric water vapour would be observed in the city.

Water consumed for domestic water requirements does not exit from the water cycle. Within several days the liquid water that is used or with-held temporarily from the water cycle would be returned to the environment to evaporate into atmospheric water vapour.

Using a new technology such as atmospheric water vapour processing in drinking-water-from-air machines may have other impacts on Nature. These include

• possibility for more people to live in a region, increasing the population density;
• increased sewage and other waste (including material waste from machines which have reached the end of their operational life);
• increased energy use (to operate the machines); and
• increased material use (to build the machines).

A recent analysis by me about the direct environmental impact of widespread use of dehumidifiers and air-conditioners dripping condensate from millions of machines since about 1950 showed that the specific humidity field at Earth's surface has been remarkably stable over the past 70 years (see the figure above and the associated earlier blog post). In fact, Wikipedia: Air Conditioning stated, "According to the IEA [International Energy Agency], as of 2018, 1.6 billion air conditioning units were installed,...." The same Wikipedia article said, "Innovations in the latter half of the 20th century allowed for much more ubiquitous air conditioner use. In 1945, Robert Sherman of Lynn, Massachusetts invented a portable, in-window air conditioner that cooled, heated, humidified, dehumidified, and filtered the air."

In summary, scenarios involving the entire human population using processors of atmospheric water vapour are unlikely, so it is also unlikely that water-from-air technologies will cause a drier atmosphere in the context of the Earth’s water cycle and natural processes of water transport and distribution.

References:

AGU (1995). Water vapor in the climate system. Special Report. Washington, DC: American Geophysical Union.

Gleick, P. H. (1998). The World's Water 1998-1999: The Biennial Report on Freshwater Resources. Washington, DC: Island Press.

Wahlgren, R. V. (2018). Water-from-Air Quick Guide. Second edition (reprinted July 2018 with minor corrections). North Vancouver, BC, Canada: Atmoswater Research.
​ 

Reading this article by journalist Julian Delia in the The Shift (published in Malta) prompted me to create a Water-from-Air Resource chart for Valletta, Malta.

More musings---see previous blog post. This time I was reading a recent issue of Eos (August 2021), published by the American Geophysical Union (AGU). One article (Climate Clues from One of the Rainiest Places on Earth, page 11, by A. J. Wight) contained a wonderful quote. "In the atmosphere, we are all connected," and the [low-level jet stream] "is part of the engine that redistributes the heat from the tropics to higher latitudes." So stated John Mejia, associate professor of climatology at Nevada's Desert Research Institute. The water-from-air industry's main resource is the water vapour in the atmosphere. Water vapour is transported great distances between regions on Earth by the global atmospheric circulation processes. We are all connected in seeking to utilize this water resource residing in our "atmospheric commons". Atmospheric water vapour is, of course, just one part of the water cycle, one of the many essential planetary cycles of natural materials.

Recently, I was catching up on my reading. An article's title caught my attention---Redirect military budgets to climate and pandemics (Nature, V 584, 27 August 2020, 521-523)---I know, I know, this article was a year old---my catch-up pile is rather high! The author was Denise Garcia, associate professor of political science and international affairs at Northeastern University, Boston, MA. She is also a vice-chair of the International Committee for Robot Arms Control, and a member of the International Panel for the Regulation of Autonomous Weapons. Garcia's article is worth reading in its entirety. But, what spoke to me was her list of four priorities, one of which is relevant directly to the water-from-air industry. The four priorities are: stop new arms races, abide by the Arms Trade Treaty, implement the 2015 Paris climate agreement, and invest in the United Nations Sustainable Development Goals (SDGs, agreed to in 2015). SDG 6 is Ensure access to water and sanitation for all. Atmoswater Research, in its own low-key way---evidenced by the content of the Atmoswater website and list of projects done for clients over the years---is trying to contribute to SDG 6. In so doing, we can claim to be part of the four priorities------helping, as Garcia said, "...steer the world towards a safer course." I like to be inspired by this role, especially when the going gets tough, as it so often does.

Registration is now open for the "Atmospheric Water, Part 3" Webinar on November 17. The registration page is at ​http://bit.ly/SGC-Nov17

Participants at this well-attended webinar had lots of questions---too numerous to answer during the Q & A period at the end of the webinar. So the three panelists were asked to reply to a set of questions---the answers were sent recently to the registered attendees. Here are my answers to the set of eight questions assigned to me. They cover a variety of topics. I hope you find the answers interesting and useful.​

• ​What effect will widespread global atmospheric water use have on the world climate?   

Note: The text in square brackets below was updated by a more recent blog post 
Impact on the atmospheric water reservoir from using water-from-air systems: an update (2021-09-27).
[The big picture is the water cycle. Every moment, myriad processes, natural and human-caused, are evaporating and condensing huge amounts of water. Liquid water that humans consume for drinking is only temporarily with-held from the water cycle (hours or days). The atmosphere contains 15.5 million million cubic meters of water according to a 1995 report by the American Geophysical Union. Various natural processes already transport and distribute vast volumes of water vapor and liquid water across Earth. Even if every single human alive in 2050 (using the UN's 2007 projection for a population peak of 9,200 million people) used water from water-from-air machines at the rate of 50 L (0.050 cubic meters) per day, they would consume (temporarily) only 0.003% of the available atmospheric water. This scenario involving the entire human population is unlikely, so it is also unlikely that water-from-air technologies will cause a drier atmosphere in the context of the Earth’s water cycle and natural processes of water transport and distribution.

Water vapor, the gas phase of water, diffuses along pressure gradients to zones of lower water vapor pressure. If a lot of water vapor was condensed into liquid water in a specific region such as a city, water vapor from outside the region would flow in immediately. No net loss of atmospheric water vapor density would be observed in the city.

Water consumed for domestic water requirements does not exit from the water cycle. Within a day or so the liquid water that is used or temporarily with-held from the water cycle would be returned to the environment by evaporating into atmospheric water vapor.

On a clearly bounded terrestrial surface such as a tropical island, atmospheric water vapor processing systems would increase slightly the annual precipitation. Let us say a large-scale AWG array is installed on an island such as Grand Turk (Turks & Caicos Islands). The island has a surface area of 18 square kilometers (1,800 ha). The AWG array produces water from the air at a rate of 75,335 cubic meters annually. This is equivalent to a rainfall of 7,533 mm over one hectare (10,000 square meters). The average annual precipitation of Grand Turk is 604 mm. This value would be enhanced by [7,533 mm/ha/1,800 ha] = 4 mm (or 0.7% annually, an amount less than the natural variability from year to year. The annual total precipitation in the year 2000, for example, was 704 mm.  

To reinforce the fact that long-term human direct impact on atmospheric water is negligible, note that dehumidifiers and air-conditioners dripping condensate have been increasingly used since the 1950s. I used NOAA global specific humidity data (measured in grams of water per kilogram of air) and subtracted the earlier 30-year 1951 to 1980 annual field from the  more recent 39-year 1981 to 2019 field. The resulting map showed several pools of higher specific humidity (+2 g/kg). These are likely related to climate change. Drying of about -2 g/kg is noticeable over the Sahara and Gobi deserts---more likely to be related to climate change than use of HVAC equipment. Over most of Earth specific humidity has been remarkably stable (+/-1 g/kg) for the past seven decades. By the way, I posted the map in the Atmoswater Research blog. Indirect environmental impacts are more likely. These will be related to the materials used in manufacturing AWGs, product life cycle aspects, and so on. Also, AWGs will enable humans to expand their footprint which could increase population density in a region, lead to increased sewage and waste disposal challenges, and increase energy use. 

These analyses indicate widespread global atmospheric water use will not noticeably affect the world climate.]

• How does the cost of atmospheric water compare for a drinking water source as compared to more conventional sources?

In a tropical climate where a chilled-coil AWG produces water at its rated capacity every hour of the year the electrical energy cost of the water will be, on average, about 0.4 kWh per liter (400 kWh per cubic meter; 1.5 kWh per US gal).

More conventional sources of water have these electrical energy costs:
- Surface water, public supply: 0.37 kWh/cubic meter (Young, 2014)
- Groundwater, public supply: 0.48 kWh/cubic meter (Young, 2014)
- Tap water, 0.46 kWh/cubic meter (Gleick & Cooley, 2009)
- Municipal water (S California): 3 kWh/cubic meter (Gleick & Cooley, 2009)
- Seawater Desalination (reverse osmosis): 2.5 to 7 kWh/cubic meter (Gleick & Cooley, 2009)
- Seawater Desalination (reverse osmosis): 2 kWh/cubic meter (Elimelech & Phillip, 2011, p. S1)
- Bottled Water: 519 to 945 kWh/cubic meter [Gleick & Cooley, 2009; thermal energy units were converted to electrical energy units (3:1) to derive these values]

It was interesting to discover that AWGs used in tropical climates are competitive with bottled water. Keep in mind the apparently cheaper conventional sources may not even be available in some water scarce regions. The desalination costs do not include the apparently difficult to monetize costs of harming local ecosystems with brine disposal.

References:
Elimelch, M. & Phillip, W. A. (2011) Supporting Online Material for The Future of Seawater Desalination: Energy, Technology, and the Environment. Science 333, 712-717.
Gleick, P. H. & Cooley, H. S. (2009). Energy implications of bottled water. Environ. Res. Lett. 4 (2009) 014009 (6pp).
Young, R. (2014). Watts in a Drop of Water: Savings at the Water-Energy Nexus. An American Council for an Energy-Efficient Economy (ACEEE) White Paper. Retrieved from https://www.aceee.org/sites/default/files/watts-in-drops.pdf 

• Is there any air cleaning value to AWG? 

If the air entering the machine is strictly indoor air, the air filter in the machine may clean the air slightly but AWGs from credible suppliers are not intended to be air cleaners.

• COST: Do you have a unit cost for AWG on a per gallon basis?

From a typical retail price list, these are the USD unit costs per US gal of water production capacity when the air temperature is 85 F and the relative humidity is 75%:
- AWG rated for 5 gal/day: $300/gal (residential quality)
- AWG rated for 10 gal/day: $420/gal (balance of list is commercial/industrial quality)
- AWG rated for 40 gal/day: $178/gal
- AWG rated for 140 gal/day: $121/gal
- AWG rated for 800 gal/day: $98/gal
- AWG rated for 1800 gal/day: $82/gal

• What is the lifetime for the equipment?

Comparable equipment is used in air-conditioning. Typical equipment lifetimes range from 10 to 20 years given proper maintenance.

• What is the lifetime for an ultraviolet lamp?

12 months. The lamp must be changed annually even if it appears to be still working because the output may have decreased below the threshold for reliable inactivation of microbes.

• Over the 35 years you’ve been studying this sector, there has been a trail of broken dreams with few companies gaining long-term traction. How has the increased prevalence of these systems and recent funding news (like the $50M to Zero Mass Water [now called SOURCE Global]) changed the conversations you’re having? And, from what sectors or geographies are you hearing the greatest interest?

Conversations have not really changed. We are still firmly in the early to late majority phase (this terminology is from a 2018 article by Paul O’Callaghan and others). This stage lasts typically 12 to 16 years. I think this stage started about 2010. So, increased prevalence of systems and the SOURCE Global funding news are just part of this stage of the AWG industry. Sectors and geographies: Oddly, just in the past few days I have seen two references to US Military interest in AWGs. Otherwise, the drinking water supply sector in the United Arab Emirates is a bit of a hot spot for interest this year.
​

• Mojave Desert nighttime humidity is as high as 50% and daytime is much lower. It would seem as though the richest source of water is at night when the availability of sunlight is least. It would seem battery use is critical. How many kilowatts is required per 1000 gallons of water?

For air with a given water vapor content, the relative humidity value increases when temperature decreases (such as at night) and the relative humidity value decreases when temperature increases (with solar heating during the daytime). Water vapor content (the atmospheric water resource) actually is quite stable from day to night to next day being related to the properties of the air mass enveloping a region.  Modeling a chilled-coil AWG operating in the climate of Las Vegas shows that water production would be unreliable year-round with this type of machine. Therefore, a desiccant AWG should be considered. An AWG having a rotary solid-desiccant dehumidifier would produce water year-round (usually reasonably close to its water production specifications) according to an ASHRAE model. For an off-grid desiccant AWG, having battery power available during the night increases productivity of the system because the atmospheric water capture process can continue 24 hours per day. An off-grid desiccant AWG could use a solar thermal process during daylight hours to heat the desiccant to release water vapor for subsequent condensation into liquid water. Desiccant AWGs can also use an electric heater to reactivate the desiccant.

The energy cost of water produced by a desiccant AWG was estimated two ways (note that kilowatt is a unit of power---the energy unit is kilowatt x hours, kWh, which is power acting over a period of time):

a. Specifications for a line of industrial rotary desiccant dehumidifiers (using electrical energy) manufactured by Hangzhou Peritech Dehumidifying Equipment Co., Ltd. (http://www.desiccantwheeldehumidifier.com/sale-2082217-industrial-rotary-desiccant-dehumidifier-silica-gel-economical-dehumidifier.html). Their 14.4 L/day model produces water using 2.8 kWh/L (10.6 kWh/US gal or 10,600 kWh per 1000 US gal). Their 1,102 L/day model produces water using 1.3 kWh/L (4.9 kWh/US gal or 4,900 kWh per 1000 US gal).

b. Using information in the SOURCE Global (formerly Zero Mass Water) Patent Application US 2018/0043295 A1. The document includes an example of operation in Amman, Jordan at 14:00 on a July day. Airflow is 90 cfm. Relative humidity is 30%. A solar thermal panel with surface area 1.5 square meters provides 700 W (at 50% efficiency) to heat the desiccant to release captured water at the rate of 0.3 L/h. This information can be interpreted three different ways because international consensus is lacking on comparing different energy sources (e.g., solar thermal versus electricity; read more at the American Physical Society Site https://www.aps.org/policy/reports/popa-reports/energy/units.cfm). We need to make this comparison because the Peritech dehumidifiers and all chilled-coil AWGs are energized by electricity.
i. Thermal energy = electrical energy cost of water = (700 W x 1 h)/0.3 L = 2.33 kWh/L; efficiency of solar thermal assumed to be 100% as per OECD/IEA publication guidelines
ii. Equivalent electrical energy cost = 0.76 kWh/L; efficiency of solar thermal assumed to be 33% as per DOE/EIA (USA) publication guidelines
iii. Equivalent electrical energy cost = 1.17 kWh/L; efficiency of solar thermal assumed to be 50% as stated in the patent application

The range of energy costs for the SOURCE Global patent application example is 2.8 kWh/US gal (2,800 kWh per 1000 US gal) to 8.7 kWh/US gal (8,700 kWh per 1000 US gal).

Has widespread use of dehumidifiers and air-conditioners dripping condensate affected in the long-term the amount and geographical distribution of water vapour in the atmosphere? An analysis using data available from NOAA suggests not. The figure above shows the difference field of specific humidity resulting from subtracting the composite means (Jan to Dec) for the 30 year period 1951 to 1980 from the 39 year period 1981 to 2019, Several pools of higher specific humidity +2 g/kg are noticeable. These are likely related to climate change. Drying of about -2 g/kg is noticeable over the Sahara and Gobi deserts---more likely to be related to climate change than use of HVAC equipment. Overall, specific humidity has been remarkably stable (+/-1 g/kg) over the past seven decades.

Reference: NCEP Reanalysis Derived data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/   

Please join us for this webinar by registering at http://bit.ly/SGC-Oct20 where you will find additional information.

Here are some product design notes applicable to atmospheric water generator products. The notes are based on an interview with Mitch Maiman, Intelligent Product Solutions by William G. Wong of Electronic Design magazine (July 26, 2020).

Essential elements

• Objective market assessment (problem being solved for user, understanding of criteria inducing customer to buy)
• Define product requirements (features, functions, cost, and volumes)
• End product must deliver on a business opportunity

Common design mistakes to avoid

• Development activities lose sight of product requirements causing project to go off course and miss deadlines
• Over-designing for the application (increases cost, weight)---scheduling problems result
• Misunderstanding cost, time, and expertise required for the product design process
• Not enough reliability testing of the new product

Best process

• Tailor the design process to the project complexity, regulatory needs, and risk profile of the client

Embrace smart products

• Incorporate sensors, processing, and wireless communications (but avoid over-design)
• Smart product design usually needs a team with a wide range of expertise---mechanical, electrical, radio-frequency, embedded systems, and application software.