Tower Anchors and Bases

When installing a tower, you’ll need to install a strong base. If the tower is guyed, you’ll also need to install anchors for the guy cables. All major manufacturers provide well-engineered plans for suitable foundations. Follow the plans very carefully. Don’t cut corners to save time or money. Take a wind workshop or two before installing your wind turbine or hire a professional.

Tower Base

Virtually all towers are mounted on concrete pads reinforced with rebar (Figure 6.13). The depth required for a foundation, known as the critical depth, is the depth that prevents a foundation (and anchors) from being pried out of the ground by the force of the wind or uprooted by freeze-thaw cycles. The critical depth of a foundation depends on many factors, such as the type and height of the tower, wind speed, depth of the frost line and soil characteristics.



Fig. 6.13: Concrete Base. Most wind turbine towers rest on a solid concrete base. This photo shows the base for each leg of a freestanding lattice tower

Freestanding towers require deeper and more robust foundations than guyed towers. The taller the tower, the stronger the foundation. The stronger the winds, the deeper and more robust the foundation. The deeper the frost line, the deeper the foundation. Some soils hold tower foundations in place better than others. For instance, clay-rich and heavier soils have more holding power than sandy soils. For advice on critical tower depth, contact the turbine and tower manufacturer.

Engineered plans are typically provided in a turbine’s installation manual. Even so, be sure to consult local building codes, soil engineers or local excavators to be sure your tower foundation is sufficiently strong.

For maximum strength, concrete bases should cure at least 28 days prior to installation of the tower. Do not place a tower on a concrete pad before that! Inadequately cured concrete weakens the strength of the concrete. Your tower and wind machine rely on a sturdy, wellcured foundation. Remember, too, that cold weather slows the curing process. More time may be required in such conditions.

Anchors

In addition to a concrete base, fixed guyed towers and guyed tilt-up towers also require anchors to attach the guy cables. Anchor options for wind generator towers are many and varied. For most wind turbines, concrete anchors are the best choice. They are created by digging a deep hole, installing rebar according to the engineered drawing, and then pouring concrete into the hole. A screw-in auger, anchor, or angle steel is then embedded into the hole and angled
towards the tower as per manufacturer instructions. Once the concrete has cured, the hole is filled in. Be sure to pour anchors well below the frost line.