Wind turbines without blades
The key to the unusual design is the whirlpool – or vortex – that arises when wind hits a cylindrical pole. Normally these vortices are considered enemies of wind turbines, but in this case they exert a force on the pole and cause it to oscillate, thereby generating kinetic energy that is converted to electricity. “We can change the natural frequency of oscillation with what we call a tuning system,” explains co-founder David Suriol. “It works with two rings of magnets that help the mast change its natural frequency of oscillation through magnetic repulsion.” Thus the Vortex Bladeless can oscillate and produce electricity at wind speeds as low as 2 m/s.
Having raised $65,000 in a successful crowdfunding campaign, Vortex Bladeless is off to a good start. But Martin O.L. Hansen of the Department of Wind Energy at the Technical University of Denmark has done the math and he is not convinced. “Any wind turbine harvests kinetic energy from the area being swept by its blades or, in this case, its pole. For a traditional turbine with 80-m blades this equals around 20,000 m²,” he explains. “An oscillating pole, on the other hand, sweeps only an area of approximately its height times the diameter of the pole, plus slightly more due to the vibrations. That’s a very long way from the area being swept by a propeller turbine.”
The Spanish start-up acknowledges that each pole captures less wind than the blades of a traditional wind turbine, but argues that this is compensated partly by the smaller footprint that allows many more poles in the same area. It estimates manufacturing and operating costs to be around 50% lower than for conventional turbines, and maintenance costs 80% lower since there are no gear assemblies, ball bearings or other moving parts. “We’re like solar panels,” says Suriol. “Silent, no maintenance and we need the same electrical installations.”
Vortex Bladeless has tested 6-m prototypes made from a composite of fibreglass and carbon fibres. By the end of the year, Suriol expects to sell a 3-m 100W Vortex for small-scale and residential use. A larger 4 kW model for private homes in developing countries is scheduled for 2016, and in 2018 the Spanish start-up hopes to build a 150-m 1 MW bladeless turbine capable of producing electricity for 400 households.