Extraordinary contra

A wildly innovative turbine that could halve the cost of offshore wind is set to go into testing in Norway. The 19-m (62-ft), 30-kW, contra-rotating vertical-axis turbine is a prototype of a design that could scale to unprecedented size and power.

Most wind turbines look like a propeller on a stick – which is fine, except once you take the concept out into the deep ocean, where the vast majority of the world's best wind power resources are, and scale it up, it's a design that makes less and less sense. All the heavy bits are right up the top, so it's difficult and expensive to build and maintain a floating version that doesn't want to tip over in the wind.

That's what makes World Wide Wind (WWW)'s contra-rotating VAWT such a fascinating alternative. All the heavy generator business is kept right at the bottom – indeed, under water and below the turbine's floating pontoon. That adds enough weight at the bottom to keep the whole thing from topping into the water, requiring only a set of mooring anchors.

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