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 phenomenon 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.
If we cool that air from 40℃ to 10℃, we should be able to extract that water difference, which is 41.7 milliliters for each cubic meter of air. Under these conditions with current technology, we could produce 147 liters of water per hour using about the same energy as 18 domestic electric kettles.
At lower humidity, such as in a desert, there is less water in the air and so the system will be less efficient. You have to cool more air to extract the same quantity of water and that requires more energy. This can make the current technology too expensive for countries where water shortages are most severe. What you need is a more efficient way of capturing water vapor.
In 1834, the French physicist Jean-Charles-Athanase Peltier discovered an interesting phenomena. If you run a current though a circuit made from copper and bismuth metal wires, a temperature rise occurs at the point where the current passes from copper to bismuth, and a temperature drop occurs where the current passes from bismuth to copper. This means by consuming electrical energy, we can provide a cooling effect without any fluids or moving parts.
It has been reported that one kilogram of this material can harvest 2.8 liters of water a day at relative humidity levels as low as 20% without any other external power source. This makes it a particularly promising technology for harvesting water in arid or desert regions of the world.
Another alternative is to use simpler cooling technology but reduce the cost of it. My team and I have been developing a water-from-air system using old fridges and freezers, in addition to other recycled components such as an old computer fan and a mobile phone charger. We hope to create a low-cost system for developing countries that also reduces waste in developed countries, particularly when solar panels are used to power the system.
But this technology is moving fast. Who