Going up cold for semi arctic testing

A delayed project to develop commercial wind turbines suitable for the harsh and cold mountain areas of semi-arctic regions entered sudden express mode in September when a trio of machines were installed in the southern Swedish fells. After three years of negotiations with officials, final permission was granted in early June to the developer, Agrivind AB. Out of six potential turbine manufacturers, only three companies -- Nordex Balcke-Dürr, Bonus Energy A/S and NEG Micon -- were able to deliver units in time to beat the harsh weather conditions that make access to the area difficult for large trucks after September 15.

This project was initiated as far back as 1995. At the time, Agrivind gained support under the European Union's Thermie energy program to install two groups of three 500-600 kW turbines (Windpower Monthly, September 1996). The local community was enthusiastic and the regional authority supported the project strongly, but the Swedish environmental protection agency, Naturvårdsverket, opposed it, saying the turbines would visually impair the landscape. The local community petitioned to support the project and after three years permission was finally granted. In place of the expired Thermie funding, the Swedish energy authority, Statens Energimyndighet, has granted a yet undisclosed amount of economic support for technical development.

Staying warm

The arctic climate is not kind to wind turbines. Blades and other parts of the turbine can become quickly coated with ice, increasing the loads and altering blade profiles, changing their stall properties. A Wind World 220 kW turbine on Pyhätunturi mountain in Finland, installed in 1993, has gone through several burned out generators because of ice build up of up to 100 kg a square metre of rotor swept area (Windpower Monthly, June 1994).

The manufacturers involved in the Agrivind project have all supplied turbines that have been specially built to cope with the ice. All three are stall regulated and fitted with blades from LM Glasfiber of Denmark. One is a Nordex 600 kW unit, the N43/600, with a tower manufactured by Swedish company Dynalite Welding AB -- marking the first time components for an imported turbine are built in Sweden. The blades are heated by microwaves, a newly developed feature. The second unit is a Bonus 600 kW Mk IV, the same model that is installed in Lammasoivi in the far north of Finland; it has an electric heating system at the base of the blades. The third is a NEG Micon 750 kW unit -- the company has not yet disclosed the method it is using to heat the blades. Each unit has a tower height of 40-50 metres and a rotor diameter of 43-44 metres.

All three manufacturers are also applying some kind of heating system to the nacelles as well as other components sensitive to cold weather. Bonus, for example, has installed the transformer at ground level inside the tower to make use of its excessive heat there. The tower has two doors -- one for the transformer and another higher up for access to the ladder up to the nacelle.

The three participating manufacturers are all newcomers to the Swedish market, where Danish Vestas and Wind World have otherwise had total dominance. All three have established local retailers this year.

The turbines were installed in a triangular formation on top of the Rodovålen mountain in the province of Jämtland. Rodovålen, located in the lower southern fells -- below the Arctic Circle -- is 830 metres above sea level and a few hundred meters above the closest village, Vemhån. The regional landscape consists of low and gently sloping mountains covered mostly by forest. The climate is arctic but not extreme. The turbines are calculated to produce about 1.2 GWh of electricity a year, but industry observers consider this to be a conservative estimate. Data on wind speed are sparse.

Huge potential

Otherwise, the expansive, sparsely populated fell region has seemingly huge potential for wind power, even though larger areas are protected for nature conservation. Several power lines pass through the area, connecting the northern hydro power stations with consumers in the far more populated south of the country. Most recently, permission was granted for installation of a Bonus 600 kW wind turbine at Suorva in the far northern fells. It was planned to go up in late summer.

The project was initiated more than two years ago by local politician Mikael Segerstrom, and has since been halted in the approval process. The turbine will be partially owned by Surovavind, a co-operative of residents from the Jokkmokk community and two reindeer owners co-operatives. The main owner, however, is state utility Vattenfall. The turbine is sited alongside a long reservoir between two national parks in the province of Norrbotten and will benefit from the existing infrastructure of Vattenfall's nearby hydro station. Wind speeds average 8-9 m/s. The machine will be adapted to the arctic climate with a heating system for the blades similar to that to be used on the Bonus turbine going up in the southern fells.