University CrestEdinburgh Wave Power Group

The Spray Turbine



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Read a pdf version of Stephen's paper: Spray turbines to increase rain by enhanced evaporation from the sea.

Stephen stretched out above the Curved wave tank using a hand-drill in place of wind energy to demonstrate the water pumping ability of his proposed spray turbine. The simple model shows how the tubular airfoils of the full-sized spray turbine would efficiently suck up water from the sea and spray it into the air.


Imagine the rotor scaled up by a factor of a hundred or so, with the hollow circular members having the cross-sectional shape of airfoils.

From the Times, December 02, 2002

How egg-beater at sea could end drought and war
By Anthony Browne, Environment Editor

"FIRST, people danced in circles, then meteorologists tried sprinkling crystals in the clouds. Now one of Britain’s leading inventors has been given a government grant to develop the world’s first rainmaker machine.

Professor Stephen Salter, the Edinburgh University engineer renowned for “Salter’s ducks” which made energy out of waves, believes that his wind-driven cloud maker could finally give man control over the weather and bring agriculture to the deserts. Done on a large enough scale, he claims, it could reverse the advance of deserts, stop sea levels rising and end the Middle East conflict. The rainmaker uses wind power to drive a 200ft high turbine that sucks water out of the sea, and turns it into water vapour through nozzles, spraying it out into the atmosphere, creating clouds. Professor Salter, 62, dismisses the incredulity of many colleagues. “They said you couldn’t make ships out of steel. They said Marconi’s radio waves couldn’t broadcast beyond the horizon. The Establishment is almost always wrong,” he said. He has persuaded the Engineering and Physical Sciences Research Council to take his idea seriously enough to award a £105,000 development grant.

The rain makers, described as looking like giant egg-beaters, would be based on catamarans and placed off the coast of desert land. They could be placed where they were most needed, depending on the weather patterns. They would not work in areas that were too dry because the artificial clouds would never generate the critical mass needed. They would be used in areas where there were already some clouds but not enough to produce rain. The machine uses an existing design known as a Darius turbine, a vertical axis turbine that spins around driven by the wind. The turbine blades have water pipes inside them, with an inlet just below the surface of the sea. The centrifugal force of the spinning blades sucks the water out of the sea and propels it nearly 200ft up inside the blades. It is then forced out of nozzles, creating a spray that turns to vapour. The salt from the sea water crystallises out and falls back to the sea.

The professor calculates that the machine would produce a cubic metre of water for one fifth of a US cent, one thousandth the cost of water produced by electrical desalination of sea water. Israel is dependent on the West Bank occupation, he says, because it provides 40 per cent of its water. The rain maker could end that dependency and help to end the conflict. He also calculates that if hundreds of thousands of machines were used for many years they would transfer so much water from the sea to the land that they would reduce sea levels by up to 3ft, reversing the rising levels caused by global warming. “Salter’s ducks”, which bob up and down on the sea producing electricity from waves, generated huge public interest in the 1970s but were killed off when the Government pursued nuclear power.

Professor Salter realises his new invention may also come to nothing, but insists it is worth a try".