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Canada

Canada

DESIGNING FOR ARCTIC SURVIVAL

A series of engineering approaches to operation of wind turbines in extreme cold weather are proving their workability in Canada and paving the way for much larger projects. Success stories are from a Lagerwey 80 turbine in Regina, Saskatchewan, a Tacke 600 kW turbine in Ontario and the Cowley Ridge plant of Kenetech turbines in southwest Alberta. Less successful are the modifications on Bonus 150 turbine in Whitehorse, Yukon Territory.

The challenges of wind plant operation in sub zero weather and powerful winter winds are now being met by a series of innovative turbines in Canada. Recent operating experience shows that wind turbines manufactured in Germany, the Netherlands and the United States, but modified for Canada, can operate reliably and economically in severe winter weather. A variety of different engineering approaches are now being undertaken to implement the modifications.

Without cold weather modification, low temperatures can potentially crack wind turbine blades, make metal parts brittle causing them to be more susceptible to stress, and interfere with the operation of lubricating oil and hydraulic fluids. But commercial cold weather turbines installed in recent years at Cowley Ridge in Alberta, Cambridge Bay in the Northwest Territories, Tiverton in Ontario, and near Whitehorse in the Yukon are paving the way for projects of a much larger scale in Quebec.

Dutch Industries in Regina, Saskatchewan, reports good performance of a two bladed, 80 kW Lagerwey turbine, built in the Netherlands and commissioned in September 1994 at Cambridge Bay. The machine supplies an Inuit community above the Arctic Circle in the Northwest Territories, reducing Cambridge Bay's costly reliance on diesel power (Windpower Monthly, November 1994).

Izaak Cruson of Dutch Industries says the Lagerwey turbine is well suited for cold weather operation. Sophisticated controls located at the base of the tower are enclosed in a heated control shed. In order to combat the extreme cold, Dutch Industries also added heaters to the gearbox and yaw motor. From September 1994 to mid March 1996, the turbine produced 238,000 kWh of electricity with high reliability, according to Cruson.

A similar success story is told by the operators of Canada's largest operating wind turbine, a Tacke 600 kW installed in October last year by Tacke Windpower of Huron Park, Ontario. The three bladed turbine, manufactured by parent company Tacke Windtechnik of Germany, has a 43 metre rotor diameter and stands on a 50 metre tubular tower. Tacke Windpower's Philipp Andres says the TW 600 CWM (cold weather modified) machine is the first of the Tacke 600 fleet designed specifically for cold climates. It can produce energy efficiently at temperatures down to minus 30 degrees centigrade, he adds, and the system automatically shuts down at temperatures below this limit.

Andres lists five specific cold weather features, beginning with heat treatment of the blade to provide an inner crystalline structure highly resistant to cold weather cracking. A second modification made for Ontario is the specially engineered gearbox oil, which reportedly gives the turbine excellent cold starting capability. The gearbox also has a heater to keep it at 20 degrees centigrade, while the nacelle is kept at about ten degrees. Furthermore, Tacke altered the computer software that controls the turbine, adding more safety and control variables and providing heat to the main electrical panel. The performance of the TW 600 CWM has exceeded expectations, says Brian Kelly, Ontario Hydro's director of environment and sustainable development. The turbine produced nearly 600,000 kWh in its first five months of operation. Its availability was at least 91% each month during this period, adds Kelly, with capacity factors of at least 27%.

Black blades

The third wind turbine modified for Canadian conditions is installed in the country's premiere wind farm, the 18.9 MW Cowley Ridge plant of Kenetech turbines on range land in the foothills of the Rocky Mountains in southwest Alberta. Completed in 1994, the plant is owned by Canadian Niagara Power and utilises 52 variable-speed, three bladed KVS-33 360 kW turbines. Kenetech's Cowley Ridge cold weather package includes blades coated with an ice-shedding black laminate, heaters in the down tower cabinet and hydraulic power unit, and cold weather treated converter components and uptower turbine control units. Software modifications have been made to deal with rapidly changing wind directions.

Kenetech is planning to build on this experience with construction of Canada's largest wind project to date. The company is planning to build two 50 MW wind farms on the Gaspe Peninsula for electricity supply to Hydro Quebec. Two hundred Kenetech advanced variable speed KVS-45 turbines, each rated at 520 kW, are slated for installation. The smaller capacity KVS-33 Kenetech model was originally specified, but the larger model is now being proposed.

The KVS-45 is rated for operating temperature ranges of minus 40 degrees C to plus 51 degrees C and includes the following cold weather specific hardware features: downtower enclosure heaters, meteorological anti-icing sensor heaters, all-weather hydraulic system fluid and transmission oil, hydraulic oil warm-up circuit, and anti-icing blade paint.

Kenetech will also install 5 MW of wind capacity on the isolated, Magdalen Islands in the Gulf of St Lawrence, using most likely the KVS-33 turbine, rated at 405 kW. However, the option of using the KVS-45 turbine could be employed but would lead to greater costs for larger foundations in the sand of the islands. The plant will be connected to the local 70 MW diesel power grid. According to Kenetech the KVS-33 has all of the cold weather features of the KVS-45 except the hydraulic oil warm-up circuit. In addition it requires the following additional features: cold configuration pitch servo-actuator, pitch servo-actuator heater bag, and hydraulic power unit immersion heater.

One project not to have been quite so successful at operating in Canadian conditions is a single Bonus 150 kW turbine commissioned by the Yukon Energy Corporation in August 1993. The machine is sited 1450 metres above sea level on Haeckel Hill, overlooking Whitehorse, and was one of the largest in Canada. It is also the largest tilt-up turbine in the world and can be raised and lowered without the use of a large crane.

Made in Denmark with blade edge heaters, the turbine has been generating electricity for the Whitehorse -- Aishihik -- Faro grid since being installed. But it has had winter weather problems including the formation of "rime ice" (low density, crusty ice that accumulates at low temperatures and high humidity) on the instruments and the blades, which drastically reduces aerodynamic performance. The Yukon Energy Corporation reports that the turbine generated 557,000 kWh in 20,856 hours from August 1993 to December 1995, with a capacity factor of 17.8% and turbine availability of 95%.

Doug Craig of Boreal Alternate Energy Centre in Whitehorse says rime icing is a major barrier to efficient wind generation of electricity in the sub-Arctic. "When this problem is solved, there is every expectation of worldwide deployment, not only in Yukon but also in Alaska, Scandinavia, Finland and Russia," he adds

In fact, says Craig, a group of three Bonus turbines will be installed north of Rovaniemi in Finland to help study turbine adaptation to the harsh, cold climate. Likewise, three Vestas turbines, also from Denmark, and three German Enercon units will be tested at two locations in Sweden's Harjedalen fells.

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