Every horizontal-axis wind turbine needs a tower. Turbines erected in the 1970s and 1980s may have been perched on lattice towers, a design that can scale to 200 ft and more. However, for the protection of the maintenance technicians who must climb the towers, it makes more sense to build them from rolled steel. These protect the technician in long climbs, and better yet, provide a structure that allows installing a service lift. What’s more, the quest for stronger wind will put more recent turbines on taller towers, 100 m and more, and that will require rethinking the design.
Taller towers for wind turbines make sense in many ways. For instance, an 80-m tower can let 2 to 3-MW wind turbines produce more power than if installed at 60 m, and taller towers will let larger turbines enter the market. Taller towers also allow putting turbines in less turbulent winds, thereby decreasing their wear and fatigue.
As OEM designers configure taller conventional towers, their limitations become obvious.
Tower designers are increasingly interested in:
• Reducing their cost because the tower- cost portion of the overall wind turbine is increasing from 10% to 20% of system cost.
• Cutting tower transportation costs.
• The interaction between tower and turbine
• Focused on reducing weight
Several designs have been proposed. One uses prestressed, reinforced concrete in tubular form. Another developer has shown detailed plans for tapered modular towers. Its developer says the continuous taper or an increasing taper is the most efficient way to handle wind-turbine loads. One design, for example, uses field-assembled panels to eliminate transportation restrictions. Shipping tower panels instead of assembled towers allows lower loads and lower load heights, which lead to shorter less restrictive routes, and hence, lower transport costs.
Adding tower panels allows increasing tower diameters and heights. There are other bonuses here. Increased diameters allow for thinner tower wall thicknesses, which uses steel more efficiently and lowers weight and cost. Flanges at the tower top and base allow for a conventional interface with the turbine and foundation. Flanges use the same mounting criteria as conventional towers.
The larger bottom diameters than conventional foundations require less depth. This eliminates need for costly embedment rings often used in conventional foundations.
Filed Under: Towers
