Two prototypes test electrical systems -- Siemens and ABB head-to-head

Two almost identical versions of a 3 MW direct drive wind turbine are being built by Scanwind Group AS, but each with its own specially developed electrical system provided by competing giants of the electrical equipment industry, Siemens and ABB. The turbines will be installed at sites in Norway and Sweden. German Siemens is providing technology for the Norwegian unit at Hundhammerfjell, while ABB will be testing its Windformer generator and power technology in the Swedish turbine -- Näsudden III -- to be erected on the large island of Gotland.

Scanwind is driving the wind technology on both units, says the company's Bengt Göransson, but ABB is only involved in the Swedish turbine, and not in the Norwegian unit as earlier reported. A main innovation of the 3 MW prototype in both cases is the use of permanent magnet direct drive generators, which eliminate the need for a gear box and slip rings, says Göransson. "No parts of the generator are in contact with each other," he says. In addition, automatic lubrication systems for blade and turbine bearings and other components need only an annual exchange of lubricants -- meaning the machines only need servicing once a year, cutting maintenance costs to what the company claims will be EUR 0.003/kWh of electricity generated, about half today's usual cost.

The 90 metre rotor wind turbines with direct drive generators do pose a disadvantage: the weight. The ABB equipped nacelle will weigh 220 tonnes, whereas the Norwegian machine's slightly different technology gives it a weight of 135 tonnes. It is for this reason that a special construction lifting device is also under development, Göransson says.

Use of the Windformer technology enables the delivery of high voltage power directly to the grid, doing away with the need for an on-site transformer. The Windformer version of the 3 MW unit is intended for use offshore or in large onshore plant.

The Siemens equipped version of the prototype, which will deliver power at a more traditional voltage level using off-the-shelf power conditioning equipment, is intended for single turbine projects on land. Scanwind believes the Norwegian fells have a large untapped wind power potential.

Both the Siemens and ABB equipped prototypes are in final design stage. Test turbines are expected to be erected by summer 2002, with hopes to go commercial in 2003. The Näsudden III test unit is being built for Vattenfall, the state owned utility, while Hundhammerfjell is built for regional Norwegian utility Nord Trøndelag Elværk. Both entities are providing about a fourth of the investment in the respective turbines. Otherwise, investment is divided among Scanwind, the Swedish/Norwegian governments and ABB/Siemens.