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How to make drinkable water
out of thin air
CLEAN TECHNOLOGY
Special to The Globe and Mail
Published
Last updated
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- 207211
- AA
California is drying up. Its current drought is ringing alarm bells across the state and the country, but it is far from being alone globally in facing water shortages.
Developed economies such as California already rely on sophisticated irrigation systems to utilize what sources it has. But what’s needed now are even smarter, 21st-century solutions.
One constantly evolving technology is desalination, which is being deployed successfully around the world, even as engineers work toward better systems that will use less energy.
Another path to drinkable water
Desalination takes undrinkable seawater and removes the salt to provide potable water. It works by pushing salt water at high pressure through a superfine membrane, which blocks salt molecules and lets the water through.
Africa’s first desalination plant was built by GE in Algiers, Algeria in 2008. The plant supplies 53 million gallons of freshwater every day, a quarter of the city’s needs.
Netherlands-based Dutch Rainmaker BV has come up with an alternative, and novel, solution to water shortages. The company, with partners in Canada and other countries, has developed a technology that can deliver water out of thin air. Its technology uses wind turbines to conjure up H20, in some cases with no access to any inflowing sources.
The company’s air-to-water system, called AW75, is already operating in extreme desert conditions in Kuwait and in the cooler Netherlands. It works without access to the power grid, with minimal operation and maintenance and no waste.
“We combine technologies that are already known,” says Piet Oosterling, Rainmaker’s founder and Chief Technology Officer. The system deploys the wind via a turbine, but instead of generating electricity it creates thermal energy to cause condensation. It works because air always contains a certain amount of water, though this varies according to temperatures and humidity. When it’s 20 degrees Celsius and the relative humidity is at 50 per cent, the air contains about seven grams of water per cubic metre of air. If the temperature climbs to 30 at the same humidity, the amount of water doubles.
“The air-to-condensation process effectively heats and cools the air to the dew point. It basically creates condensation and makes it rain,” says Michael O’Connor, Rainmaker Worldwide’s Peterborough, Ont.-based CEO. The condensed droplets are collected into a storage compartment.
The heart of the air-to-water unit is the device’s wind-fed power unit. Inside the nacelle at the top of the tower there’s a proprietary compressor (heat pump). The system converts wind energy to thermal power, which, in turn, feeds the water production unit attached to the tower. The turbine forces air through a heat exchanger, cooling the air and forming condensation. When the temperature falls below its dew-point, water droplets will form. These are collected in a water storage compartment.
The company’s prototypes in Kuwait and the Netherlands each produce an average 7,000 litres per day of water. The unit in Kuwait has managed to produce 8,700 litres a day at temperatures of 28 degrees and 40 per cent relative humidity.
The company will not say where else it is testing the technology – there is a French company testing a rival system - but says it has potential in countries such as Saudi Arabia, China, Indonesia and India.
Prototypes of the air-to-water system are installed in both Kuwait and the Netherlands. (DUTCH RAINMAKER)
Air-to-water technology is not viable for colder climes, such as remote communities in Canada’s North, some of which have suffered from polluted supplies or have to truck in water via ice roads. For such climates, Oosterling says Rainmaker has another technology that the company calls water-to-water.
This unit also uses wind to produce thermal energy, but rather than pull moisture from the air it heats water from existing supplies and sends it through a membrane. It’s different than conventional reverse osmosis (RO) membrane filtration because it only allows water vapour to pass through, by varying the pressure on each side of the membrane.
The water-to-water unit can be used to desalinate and to filter brackish water; the first model can produce up to 95,000 litres of water per day, enough for a town of between 1,800 and 4,000 people.
Oosterling says he is discovering that producing clean water from the wind may be useful in ways he didn’t anticipate, for example in the mining sector. “It’s something I never envisioned,” he says.
But for now, he is focused on trying to serve the needs of the 783 million people who don’t have regular access to clean water (according to the United Nations). “It can be used where the infrastructure is not tremendous,” he says. “It has to be simple and people have to be able to understand it.”
For more innovation insights, visit www.gereports.ca
This content was produced by The Globe and Mail's advertising department, in consultation with GE. The Globe's editorial department was not involved in its creation.
