A highly innovative turbine that could halve the cost of offshore wind power is being tested in Norway. The 19-metre-long, contra-rotating vertical-axis turbine is a prototype design that could be scaled up to unprecedented size and power.
Most wind turbines look like a propeller on a stick. That works very well, but as soon as you scale up the concept and take it to the deep ocean, where wind is available in large quantities, the design makes less and less sense. All the heavy components are on top, so it is difficult and expensive to build a floating version that doesn't topple over and is easy to maintain.
Twice more power generation
This is what makes World Wide Wind's contra-rotating floating wind turbines so fascinating. All the heavy lifting is at the bottom - underwater and under the turbine's floating pontoon. That adds enough weight at the bottom and only necessitates a set of anchors. This new wind turbine can generate twice as much power and halve the cost of the generator. This makes the system more scalable. Because the turbine is maintained at the bottom and not hundreds of metres high in the sky, maintenance is also cheaper.
Counter-rotating turbine
generator's rotor and stator are connected to a pair of vertical-axis turbines, each with three blades at a 45-degree angle to the tower's main axis. The lower turbine is set to rotate in one direction while the upper one rotates in the other direction. Through a cleverness, the dual, counter-rotating wind turbine always tilts to an optimal how, regardless of the direction the wind is coming from. With the two turbines rotating in opposite directions, the speed at which the rotor turns in the stator is effectively doubled.
Lower wake effect
torsion exerted on the structure by the wind is effectively neutralised by the two counter-rotations. In addition, the conical swing of each rotor reduces the speed of the intersection and produces a smaller wake effect, which means that the wind turbines take less 'wind out of each other's sails'. in practice, the wind turbines can therefore be set up closer together. As a result, more energy can be generated from a given area and fewer cables need to be laid.
Smart material choices would allow the turbines to be scaled up to a height of 400 metres, according to World Wide Wind. A single turbine could thus generate 40 MW - almost twice as much as the world's largest wind turbines currently do.
