Precast Solutions - July/August 2008 - (Page 25)

DANISH TOWERS PRECAST CONCRETE WIND POWER AND THE PRECAST FOUNDATION PIERS FOR WIND CONCRETE INDUSTRY The National Renewable Energy Laboratory (NREL) and the American Wind Energy Association (AWEA) as well as other alternative energy Web sites provide conclusive data that support strong future expansion in U.S. wind power. Wind power unquestionably is going to play a major role in the way the United States and the rest of the world generates power. Here are some of the reasons why: • Wind is an inexhaustible and affordable energy source. • Wind power improves air quality and does not contribute to global warming or climate change. • Wind-generated power costs are declining (since 1999, wind-generated power cost has dropped almost 50 percent). • Very high fuel costs and global oil prices remain Since the mid 1990s, Danish firm Per Aarsleff, and more recently its U.K. subsidiary Aarsleff Piling, have installed driven precast concrete piles for hundreds of wind towers in poor soils where ground conditions are not suitable for a cast-in-place concrete foundation. Square precast concrete piles are symmetrically driven into the ground at both inward and outward angles around the tower location in a round or octagonal configuration. The single-piece and segmental precast piles are made by Per Arsleff’s company in Denmark, Centrum Paele, and by Arsleff Piling’s company in the United Kingdom, Centrum Pile Ltd., the largest U.K. manufacturer of continuously reinforced concrete piles fabricated and tested according to the new European Standard (BS EN12794:2005, “Precast concrete products-foundation piles”). Centrum Pile invested extensively in the latest concrete batching, transfer and form-filling equipment and uses a fully robotic pile cage fabricator to produce a standard range of 200 to 400 millimeters (8 to 16 inches) square sectioned piles. HOW IT WORKS Illustration courtesy of The Concrete Centre, England WHY PRECAST CAN OUT-COMPETE WIND TOWER COMPETITORS 1. Transportation via trucks is a problem for largerdiameter steel tower sections. Precast concrete tower sections can be shipped without special transport clearances and are produced locally. 2. Competitive cost favors precast concrete over steel for larger and taller wind towers where the wall thickness and cost of steel fabrication becomes prohibitive. 3. Greater load-bearing capacity is provided by precast concrete piles manufactured under factory-controlled conditions than that of cast-in-place concrete piles. 4. Local materials and labor are used in the fabrication and installation of most precast concrete components as compared with imported steel. 5. No soil disposal and landfill costs are generated by driven precast concrete piles, compared with deep cast-in-place concrete foundations for wind towers. 6. Lower transport costs for precast concrete than for imported steel due to weight and proximity. 7. Shorter on-site construction is possible with prefabricated precast concrete tower segments than with cast-in-place or steel alternatives. 8. Greater vibration-damping capacity favors precast concrete wind tower systems. JULY/AUGUST 2008 | PRECAST SOLUTIONS 25

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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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