The Atlas Concrete Tower Base can be 30 to 40-m tall, letting turbines work in stronger winds.
At AWEA’s recent WINDPOWER 2012 tradeshow, a precast concrete manufacturer unveiled its 40-m tall concrete wind-tower base with tours of its Conley, Ga. facility. Guests got a first-hand view from inside and outside the prototype built on company grounds. The base is intended to provide a less expensive structure than an all-steel tower for raising towers to 100 meters and more to reach higher wind speeds and increase turbine efficiency. A conventional steel tower would be placed atop the base.
Tindall Corp. designed the Atlas Concrete Tower Bases (CTB) with the intention of raising hub heights to 130+ m. “After three years of development, the innovative design provides a reliable, efficient solution that eliminates height barriers,” says Tindall Vice Chairman William Lowndes IV. The CTB uses a precast tower base that is GL-Certified, developed, and manufactured in North America. The twenty concrete pieces that form the CTB are connected with about 13 miles of post-tensioned cable.
According to the company, it is the first of its kind in North America and benefits include a 50% or more reduction in foundation concrete, reinforcing steel, and installation costs. In addition, the 40-m high CTB supports 1.5 to 3+MW turbines on steel mono-towers from 70 to 100 m. The base uses no bolts. Post tensioned is by tendons only. Components can be factory manufactured or site cast.
The mold that forms a stave (triangular) section can make two a day.
“The 16-m diameter inverted conical base supports a concrete transition and multiple circular sections that form the platform for support of conventional steel monotowers. A clever ring foundation, with a larger than conventional diameter, provides maximum resistance to bending and overturning,” says Lowndes. This allows for minimal foundation thickness. The design of the base takes full advantage of gravity, effectively resisting overturning loads and preventing uplift. Lastly, it helps reduce life cycle costs for blades, turbines, and the upper tower.
Vertical and circumferential post tensioning places the transition zone in a state of bi-axial compression, protecting against fatigue from high-cycle loading.
The company’s CTB lets contractors reduce excavation costs, labor costs, and shorten the project schedule. Thermal cracking concerns are said to be eliminated because there are no mass concrete pours. And says Lowndes, it will be strong and stable fifty years from now. WPE
Filed Under: Construction, News, Towers
