Where does drinking water come from? For people living in parts of the world where fresh water is plentiful, it's not much of a mystery.
However, for people living in the Middle East, parts of Africa, and other hot, dry places, the water situation is more complex. There, people depend on turning salty ocean water into fresh water, a process called desalination.
Water desalination is a life-saving technology; without it, many people simply wouldn't have access to fresh water. However, desalination is also costly, especially to the environment.
Some desalination plants use high amounts of pressure to force water through membranes that remove the salt. Other technologies involve boiling sea water, and then condensing the salt-free steam that results. Both processes require huge amounts of energy, consume lots of fossil fuels, and emit tons and tons of carbon dioxide into the atmosphere, contributing to global warming.
On very large scales, desalination is going to burn a lot of energy, no matter what you do. However, on smaller scales, say desalinating enough for a small community or village, there may be a better way.
Researchers at New Mexico State University have developed a low cost, low energy system. Their technology uses two, 30 ft high columns to create areas of very low pressure in the columns' head space. When the pressure is low enough, water will evaporate at near room-temperature.
The system requires so little energy that it could run on waste heat produced by refrigerators and air conditioners. It's still in development, but for small communities without access to fresh water, the technology could soon make a big difference.