Untapped field

An ambitious project has been launched to create a local renewable energy network by installing mini wind turbines in up to 21,000 farms across the UK.

The project, called Windcrofting, has been proposed by Scottish wind farm company Proven Energy, which specialises in small-scale, high-performance wind turbines.

The idea behind Windcrofting is simple. Farmers sign up to the project and Proven Energy installs wind turbines in hedges on the farms, so no usable farmland is taken up.

Proven Energy then pays the farmer a small amount of ground rent and sells the generated power back to him at a rate that Gordon Proven, the firm's founder and chief research engineer, estimates would be half the price he would pay his local electricity company. Any extra power can then be exported.

'Windcrofting is a completely different idea because it works on the principle that we can finance a distributed wind farm and install as many on ordinary farmland as the local electrical connection can handle,' said Proven. 'This means we have a distributed wind farm which has huge potential, but does not need any grid reinforcing.'

The scheme will use Proven Energy's patented 15kW machines — the largest in its family of turbines — which are only about one-tenth the size of conventional turbines. One of the benefits of the smaller scale is that there are likely to be far fewer objections from local residents on environmental grounds, said Proven.



Financially viable

With about 180,000 UK farms, the potential market for the scheme is huge, and the company's first goal is to install turbines in 3,000 of them. To make the project financially viable, a minimum of 1,000 will have to sign up.

apart from their size, the turbines differ from conventional machines in a number of ways. Conventional turbines have to cope with powerful destructive forces from the wind and the forces they themselves create in operation. Proven designed a turbine configuration to nullify as many of these destructive forces as possible.

Proven Energy's turbine design uses a patented pitch control system known as Zebedee, which allows the turbine to react, flex and adjust to all aerodynamic and centrifugal forces. Essentially no more than a rubber hinge, the device allows each of the turbine's three blades to 'cone' out of the wind.

This means that when there is no wind, the blades sit flush, perpendicular with the vertical axis, but move outward when the wind blows. Proven claimed this makes the turbines extremely robust.

'This machine will run in hurricanes without shutting down as there is no bending strain on the blade itself,' he said. 'There is also a secondary hinge that distorts with the centrifugal torque and aerodynamic forces. It changes the pitch of the blades so they stall if the forces increase too much, acting as a natural brake. This reduces the area that is exposed to the wind.'

The blades are also robust, made from an advanced glass thermoplastic, making them tough yet flexible. 'We have them on the Greenland ice shelf and in the Saudi Arabian desert so it's a tough machine,' said Proven.

His company is also working with Shell to install nine turbines on an unmanned oil rig in the North Sea where they will have to run for three years unattended. According to Proven, this would not be possible with bigger, conventional turbines, which usually need regular maintenance to continue functioning properly.



Challenging environments

The first Windcrofting turbines are likely to be installed within about a year, but Proven Energy is already expanding its portfolio in other, even more challenging, environments. It has won a contract to install turbines on the proposed Belgian Antarctic Research Station, a base due to be built in 2007-2008 that will be powered almost entirely by renewable energies.

Photo Credit: Mr J Varnom 2004