Precast Solutions - July/August 2008 - (Page 24)

NETHERLANDS DEVELOPS ADVANCED PRECAST TOWER SYSTEM Advanced Tower Systems (ATS), Netherlands, a joint venture of Mecal BV and Hurks Bouwgroep BV, has developed a precast concrete segmental tower with tubular steel sections on top. Mecal is an independent engineering company with more than 10 years of experience in wind turbine technology, and Hurks Frans Brughuis Bouwgroep is a large general contractor and builder of high-tech precast concrete construction. “Larger and higher wind turbines are the global trend in the rapidly expanding wind energy market,” explains Frans Brughuis, managing director for ATS. “We have developed an economically viable alternative to steel towers for wind turbines of 1.5 megawatts or more and at hub heights (tower elevations) of 80 to 150 meters (263 to 492 feet).” Precast concrete tower sections are erected by a sixperson crew (including mobile crane operator) using a mastclimbing work platform that adjusts to each tower section’s taper. Photos courtesy of WEC Turmbau GmbH and The Concrete Society, England Larger hub heights (more than 1.2 times the rotor diameter) of up to 160 meters (525 feet) are more likely to deliver up to 60 percent efficiency, or energy yield, than shorter wind towers (see precast.org/wind). “At heights of more than 100 meters, or about 330 feet, the atmosphere is characterized not only by higher wind speed,” asserts Brughuis, “but by more constant wind speeds and less turbulence.” Less turbulence translates into lower fatigue loads on the wind rotor and therefore more energy production efficiencies. The real beauty of this wind power scenario of physics and meteorology is what it all portends for the precast concrete industry. Higher wind towers require stronger and stiffer tower construction. Larger tower circumferences made of tapered steel cylinders pose transportation issues, as a diameter of 4 to 4.5 meters (13 to 15 feet) are limited by overpass clearances on roadways both in Europe and in the United States. Steel towers for land-based sites are generally feasible only for hub heights under 100 meters (328 feet), as higher towers would require steel wall cross sections of more than 30 millimeters (about 11/4 inches) thick or very expensive components. Like the escalating cost of oil, steel prices also have been increasing. ATS has developed a precast concrete tower system that eliminates the transport clearance problem and also enables rapid on-site installation. What this all means is that for taller and more powerefficient wind towers, precast concrete systems can offer economically feasible alternatives to steel construction. Other European companies have also developed hybrid towers made of precast concrete and steel, and Spain has installed hybrid towers with heights greater than 100 meters (328 feet). WEC Turmbau GmbH (a subsidiary of Enercon) has developed a new tower construction technique using precast concrete tower ring sections. A minimal number of people are required for tower erection, including the crane operator and four people on the mastclimbing work platform to guide the precast sections into position. 24 PRECAST SOLUTIONS | JULY/AUGUST 2008 http://precast.org/wind

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Precast Solutions - July/August 2008 Contents What You Should Know About UHPC A Winning Hand Fresno Federal Expanding U.S. Wind Power Precast Concrete Pipe

Precast Solutions - July/August 2008

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