Canadian CWT Power Inc is hoping to launch a highly competitive four-bladed vertical axis wind turbine. The company says the curved-blade Darrieus wind turbine concept has now been thoroughly tested and developed for a decade and a prototype is now ready for the market. CWT Power points out that the inherent simplicity of the vertical axis concept is highly suitable for remote and cold region markets because of its ease of maintenance, its efficiency, its latest developments in aerodynamics, materials and blade manufacturing. The turbine is also suitable for developing countries because bearings and turbine are on the ground, making the machine easy to erect and maintain and allowing the support structure to be lighter.

A highly competitive Canadian four-bladed vertical axis wind turbine could be on the market within 12 to 18 months if Michael Carten, president of CWT Power Inc, has his way. CWT, of Calgary, Alberta, is the successor to Adecon Energy Systems Inc, a manufacturer of vertical axis wind turbines (VAWTs) and veteran of the Canadian wind scene.

CWT now owns ten SL-38 curved blade VAWTs, manufactured in Ontario by Adecon and installed at Pincher Creek, Alberta in 1993-94. Last year the company acquired control of Adecon Energy Systems Inc, Adecon Research Inc and Adecon Inc, along with the intellectual property relative to the manufacture, installation and operation of the Adecon VAWT design, as well as proprietary blade bending equipment and certain tools used in the manufacturing process.

Carten is now confirming the turbine power output cost curve under different wind conditions at Pincher Creek. The turbines were apparently not electronically monitored by Adecon. Natural Resources Canada has contributed some $50,000 for the evaluation. "My plans are to ascertain if these machines are commercially viable and if so, I'll raise the capital to produce them and develop new projects," says Carten.

His optimism might be short lived, though. Two of the 30 metre structures have toppled, following metallurgical failures which are still under investigation. They appear attributable to poor quality control by Adecon in the manufacturing and installation process. Carten stresses that this VAWT experience "parallels that of other wind turbine manufacturers in the R&D phase."

Two of the Darrieus-type turbines remain at a 100 kW design output, while eight are now rated at 150 kW, having had their blades redesigned to sweep a greater area. The turbine utilises a high height (30.5 m) to diameter (21.5 m) ratio to achieve increased energy capture (see table for SL-38 specifications).

The Pincher Creek Project is one of only two wind power facilities constructed internationally since 1985 using curved blade Darrieus type VAWTs, the other being a facility installed by FloWind, according to Carten.

The CWT turbines were designed by Peter South, who is retired from Canada's National Research Council and formerly chief engineer with Adecon. His design philosophy was to develop a turbine that uses uncomplicated technology to achieve low cost, reliability, durability and ease of maintenance. The objective was to create wind turbines that would run in all weather conditions and could be easily serviced by individuals with basic mechanical and electrical skills.

Carten says, "The curved-blade Darrieus wind turbine concept has been the subject of considerable research, development and commercialisation since its rediscovery by South and Raj Rangi at the National Research Council of Canada in the 1960s. In the early 1980s, at least five companies in Canada and the US (including AESI and Indal Technologies of Canada) were actively designing and testing prototypes and installing the first commercial units. Today, more than 500 of the first generation commercial turbines are in operation and are estimated to have produced well in excess of 500,000 MWh of electrical energy and logged more than 10 million hours of operation."

Carten sees a renewal of commercial interest in VAWTs in Canada and the US, pointing to the fact that turbines from US VAWT competitor, FloWind Corp, are still operating in California ten years after they were installed. He also points out:

¥ that the inherent simplicity of the Darrieus concept (and therefore its potential fo high reliability and low cost) has not been significantly exploited because the technology has experienced only one cycle of commercial development

¥ that the large remote and cold region markets for wind power require design simplicity and ease of maintenance, which favours the Darrieus design approach

¥ that the Darrieus is as efficient as, and, in some cases, more efficient than, horizontal axis turbines

¥ that new developments in aerodynamics, materials and blade manufacturing, structural design, control systems and electric generators, could be combined into highly competitive designs.

Carten would like to market the turbine in developing countries for which many of their features are ideally suited. In particular, with the bearings and turbine on the ground, they are easier to erect and maintain, and the support structure can be lighter. The innovative VAWT bearing takes the load of the rotor and permits the use of off the shelf transmission and generation components which can keep the cost low. Moreover, the design simplicity and ease of maintenance of the Darrieus concept makes it suitable for large remote and cold regions such as the Canadian north.

"Our strength is in blade manufacture and bending. However, the first generation SL-38 turbines must play technical catch-up to the latest generation of horizontal axis machines," Carten says. "Our Pincher Creek operation is essentially a laboratory to study the turbines, although we have a 20 year contract to sell energy to TransAlta Utilities Corporation under the Alberta Small Power Research and Development Act. In theory, the turbines should be the lowest cost machines around, some two-thirds the cost of the latest variable speed turbines, and they are easily maintained. The four-bladed design smooths the power curve, but requires further study."

Lawrence Schienbein is directing and managing the assessment under a consulting agreement with CWT. Schienbein is currently with Battelle Memorial Institute Pacific Northwest Laboratories, and was formerly wind engineering manager with VAWT pioneer, Indal Technologies, and vice president of research and engineering with FloWind Corp.

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