Luke Skywalker wasn’t just a farmer. In the original 1977 Star Wars film, the lead character was desperate to leave his home planet of Tatooine, where his family farmed moisture from the atmosphere using devices called “vaporators”. In the planet’s hot and dry desert landscape, moisture farming was an important activity for survival.
But could this principle of drawing moisture from the air to provide drinking water work in the real world? Researchers and I are working on technology to turn it from science fiction into reality. And now a new study has demonstrated how one device could work even in dry desert conditions using only the power of the sun.
If you sit in your garden on a hot, humid summer day with an iced glass of water, you will notice water droplets forming on the outside of the glass. The Star Wars vaporators on Tatooine may have worked using a similar principle. Cooling down warm air produces condensation, which can then be collected. Rain is actually a natural phenomena of the same principle. When warm, humid air cools, it loses its capacity to maintain its water content and precipitation occurs in the form of raindrops.
Air naturally carries water vapour, and the warmer the air and the higher the relative humidity, the more water vapour it can carry. So technology that generates water from air is most suited to warm and humid climates. At 100% humidity, the air at 40℃ contains about 51 millilitres of water per cubic metre of air. For the same humidity at 10℃, the air contains only 9.3 millilitres.
If we cool that air from 40℃ to 10℃, we should be able to extract that water difference, which is 41.7 millilitres for each cubic metre of air. Under these conditions with current technology, we could produce 147 litres of water per hour using about the same energy as 18 domestic electric kettles.