New concept from UK manufacturer

In a dramatic departure from its previous wind turbine concepts, Britain's Wind Energy Group (WEG) has come up with a radical design for a 600 kW machine that is also distinctive from the majority of its competitors. In a project funded jointly by Britain's Department of Trade and Industry and the European Union's Joule II programme, WEG has opted for a downwind flexible machine.

Details of the turbine -- to be called the MS4-600 -- were unveiled in May at the European Union wind conference in Sweden by WEG's John Armstrong. He says that in looking for a commercial successor to its current 400 kW MS3, the company is continuing its low weight policy. The new turbine weighs in at about two-thirds the weight of its 600 kW upwind rivals, he claims.

Unlike the two-bladed WEG MS3, the MS4 is three-bladed. It is likely that WEG has chosen this route after studies into the aesthetics of wind developments consistently show a preference for three blades on turbines. WEG believes that for a three-bladed machine, downwind free yaw operation offers the best route to reduced loads and therefore lower weight and cost. Flexible blades are needed for yaw stability, but they also reduce storm loads by up to 50%. Stall regulation and two speed operation are further departures from the new design's predecessor. Another feature is ease of installation. With an eye on a growing market in remote regions, WEG has designed the turbine so that it can be winched into place. Only a small off-loading crane is needed to install and maintain it. This means it is suited to rugged sites with poor access for the large cranes or where such cranes are not available.

In the wake of its programme of strengthening the pitch linkages on all its MS3 machines after blade losses in the violent storms of 1993 at Cemmaes in Wales, WEG has made a virtue of the turbines' ability to survive the harsh wind regime there. In keeping up the tradition, the new MS4 is designed for turbulent wind conditions. Yet the ability to vary the rotor size from 41 metres up to 45 metres optimises output in low wind speed areas of the world.

The prototype machine is already under production at the company's base in Southall, Middlesex, which is also the headquarters of its parent company -- construction giant Taylor Woodrow. The turbine is destined for the Centre for Alternative Technology at Machynlleth, mid Wales -- only seven miles from the Cemmaes wind farm. The machine is expected to be installed in November and will be exposed to severe operating conditions right from the start, says Armstrong.