There’s water in dem dar clouds!

With seawater covering seventy-one per cent of the Earth’s surface, at an average depth of four kilometers, and another 1,000,000,000,000,000 liters of water in the first kilometer alone of the earth’ atmosphere, water could hardly be described as a rare element. Its more a case of ‘water water everywhere and not a drop to drink‘. I’m going to highlight a few different ways in which renewable energy can be used to produce drinking water.
One of the readers last week commented that use of wind turbines or wave energy to power desalination would be a great idea. Well in Perth Australia they are doing exactly that. Perth Australia has now established one of the largest desalination plants outside of the Middle East and set up a wind farm to power it. Electricity for the desalination plant, which has an overall 24MW requirement, comes from the new 80MW Emu Downs Wind Farm, located 30km east of the town of Cervantes. (anyone else see the irony here… Miguel Cervantes, …Don Quixote, Windmills?)

Speaking of windmills, another Australian, Max Whisson, an energetic septuagenarian inventor, believes he can solve the current water crisis with his Water Windmill invention, a unique technology to extract moisture from the atmosphere. The concept is to use windmills to cool air and extract water directly from the air and was partly inspired from an African beetle, Stenocara, who manages to be completely water sufficient by standing on his head in the desert and using cooling plates on his body to extract water vapor from the air. Here is a link to a video
showing the wind turbine in operation. The “Whisson Windmill” will make it possible to get adequate water anywhere at any time, drought or no drought” says Dr. Whisson. Given that between 1% and 4% of the earths atmosphere is water vapor, he may be onto something.
Max also had another concept he called a ‘Water Road’ which Nick Bruce featured on his podcast, the CleanTech Show. In the “Water Road”, seawater is transported inland in black pipes covered with Perspex; solar energy heats up the water at it travels through the pipes to 70-80 C. Water vapor is produced and condensed several hundred kilometers inland to provide water for irrigation. The genius of both of his ideas is the direct conversion of primary energy to the desired end result which is pure water. They are very early stage, conceptual as far as I can tell.

Another technology being developed by the New Mexico State University uses low grade heat and a vacuum to run a distillation process. The system can convert saltwater to pure drinking water on a round-the-clock basis – and its energy needs are so low it could be powered by the waste heat of an air conditioning system. At the risk of losing you, here’s the 101 of how it works. The system consists of two 30-foot vertical tubes – one rising from a tank of saline water and the other from a tank of pure water – which are connected by a horizontal tube. The natural effect of gravity creates a vacuum in the air space above the water column. The lower pressure in the headspace causes water to evaporate at a lower temperature, (this is why water boils at lower temperatures on top of a mountain). Then they use waste heat, for example from an air conditioning system, to heat up the saline water (e.g. seawater or brackish groundwater) to 10 -150 C more than the freshwater. Water vapor from the salt water column travels across the horizontal bridge and condenses in the freshwater column.
Commenting on its energy efficiency, one of the inventors, Nirmala Khandan, an environmental engineering professor in NMSU’s Department of Civil Engineering said “That’s the trick of this vacuum, we don’t have to boil the water like normal distillation, so you can use low-grade heat like solar energy or waste heat from a diesel engine or some other source of waste heat.”
So there you have it. Both energy and water are present in abundance on the planet and if we can use our ingenuity, we may be able to harness and access both in a sustainable manner.

Paul O’Callaghan is the founding CEO of the Clean Tech development consultancy O2 Environmental. Paul is the author of numerous papers environmental technologies and lectures on Environmental Protection technology at Kwantlen University College. He is chair of a technical committee on decentralized wastewater management in British Columbia, is a Director with Ionic Water Technologies and an industry expert reviewer for Sustainable Development Technology Canada.

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