For those who live in big Western cities or affluent suburbs, where your drinking water comes from is an almost invisible part of daily life. Maybe you sip from a hoard of Smart Waters in your fridge or pour a glass from an aesthetically pleasing water filtering pitcher. Or if your home is particularly fortunate — right from the tap.
But for billions of people worldwide — including in U.S. cities like Flint, Michigan — accessing clean drinking water is a top-of-mind and urgent crisis.
Building large desalination and water treatment plants can offer some relief to this problem, but these efforts can be costly to start and maintain. As an alternative, engineers have been working on a much smaller-scale technology (roughly the size of a cornhole table) that would use the power of sunlight to snatch moisture from the air and condense it into drinkable water.
Such efforts may seem like, literally, grasping at thin air, but a recent analysis from Alphabet’s moonshot “factory” X (formerly Google X) has demonstrated that these technologies may have what it takes to make a significant impact.
“Our analysis demonstrates that daytime climate conditions may, in fact, be sufficient for continuous-mode AWH [atmospheric water harvesting] operation in world regions with the highest human need,” Jackson Lord, lead author of the paper and previous X employee, tells Inverse.
“We show that AWH could provide [safely managed drinking water] SMDW for a billion people.”
The team published their findings in October in Nature.
What is atmospheric water harvesting?
When you imagine how drinking water is collected, maybe you picture idyllic glacial run-off, drilling deep into the earth for a well, or even slogging ocean water on land to be desalinated.
Atmospheric water harvesting (AWH), however, takes a different approach. As its name suggests, these technologies use fans and heat to capture moisture from the air — such as on a humid day — and condense it down, drop by drop, into drinkable water.
These devices come in two major flavors:
- Diurnal (single cycle) dew harvesters
- Continous (multi-cycle) fog harvesters
Opting to run largely on solar power, these devices may sound at first glance like the perfect eco-friendly solution. But critics of the technology aren’t so sure, citing low supply issues. After all, weather isn’t universally humid day-to-day, let alone around the world.
Lord says the main goal of the recent paper was to show investors in this technology that engineers could overcome supply issues.
“Low specific yields and low daytime relative humidity have raised questions about atmospheric water harvesting performance in liters of water output per day,” Lord says. “Our study attempts to address this. We think solar-driven, continuous-mode AWH devices sized to produce sufficient daily drinking water output for an individual or family could address both the water quality and the water access dimensions of safely managed drinking water solutions at the household level.”
What X did — To make their analysis, Lord and colleagues used performance data from a number of existing AWH devices.
The team compared WHO and UNICEF datasets of regions most in need of cleaning drinking water (which included sub-Saharan Africa, South Asia, and Latin America) and climate data that showed where weather conditions might best support AWH.
Through their analysis, the team found that strong sunlight and humidity above 30 percent was enough to meet a goal of at least five liters of water per day per person. The team explains in their paper that this means not every region is equally effective; for example, an arid region of central Africa may have much lower humidity levels than regions closer to the coast of the continent.
Shortfalls in humidity like these or seasonal changes might require users to reply on surplus or storage — such as collecting rainwater — Lord and colleagues report that the widespread use of AWH devices could help provide 1 billion people with adequate and clean drinking water.
X has stepped away from developing this technology further (for cost reasons) itself but has shared its findings and technical specs for all to use.
Next steps — While their recent study shows AWH has a considerable future in providing sustainable, clean water sources, Lord says that this evidence is only the first hurdle of many more to come.
“Product affordability and adoption require parallel financial and socio-cultural efforts such as scaling availability of loans, promoting awareness of waterborne disease risk and increasing women’s influence over community decisions,” the authors write in the paper. “Our analysis demonstrates that daytime climate conditions may in fact be sufficient for continuous-mode AWH operation in world regions with the highest human need.”
Update: This story was updated on November 4th to clarify the data source used to assess the technology’s global potential.
Abstract: Access to safely managed drinking water (SMDW) remains a global challenge, and affects 2.2 billion people. Solar-driven atmospheric water harvesting (AWH) devices with continuous cycling may accelerate progress by enabling decentralized extraction of water from air, but low specific yields (SY) and low daytime relative humidity (RH) have raised questions about their performance (in litres of water output per day). However, to our knowledge, no analysis has mapped the global potential of AWH12 despite favourable conditions in tropical regions, where two-thirds of people without SMDW live. Here we show that AWH could provide SMDW for a billion people. Our assessment—using Google Earth Engine—introduces a hypothetical 1-metre-square device with a SY profile of 0.2 to 2.5 litres per kilowatthour (0.1 to 1.25 litres per kilowatt-hour for a 2-metre-square device) at 30% to 90% RH, respectively. Such a device could meet a target average daily drinking water requirement of 5 litres per day per person. We plot the impact potential of existing devices and new sorbent classes, which suggests that these targets could be met with continued technological development, and well within thermodynamic limits. Indeed, these performance targets have been achieved experimentally in demonstrations of sorbent materials. Our tools can inform design trade-offs for atmospheric water harvesting devices that maximize global impact, alongside ongoing efforts to meet Sustainable Development Goals (SDGs) with existing technologies.