Using wind power to generate energy isn’t a new concept. For hundreds of years, the classic windmill harnessed the wind’s energy. Today, modern wind farms use wind turbines to generate energy on a much larger scale. These massive structures require costly construction materials, land leases, and maintenance. Specifically, the wear and tear on traditional spread foot foundations need knowledgeable partners to manage repairs or, once the turbines have outlived their service life, need complete replacement.
Although wind turbine generators, transmission lines, and land costs are generally fixed, tower foundations can be unpredictable, leading to unexpected expenditures. Selecting the best foundation strategy for a project can result in significant cost savings due to fewer repairs, as well as extending the life of the structure.
Today, the next generation of wind turbine foundation solutions are stabilizing design and construction costs. These advanced foundation solutions help fill the gap following expiration of the Production Tax Credit (PTC) and reduce the levelized cost of energy (LCOE). As the exclusive provider of the Patrick & Henderson (P&H) soil and rock anchor foundations and the most experienced designer of the P&H tensionless pier foundation, Terracon can bring value to your next wind project. There is a P&H solution for most every wind project, providing construction cost savings and performance risk reduction.
Wind power is capital intensive, with land-based, utility-scale wind projects running about $2 million per turbine installed. About 68 percent of the total cost is attributed to the turbine and 23 percent to the balance of plant, which includes the foundation. The foundation accounts for about 17 percent of the balance of plant. Through testing, research, and geostructural design experience and innovation, a more streamlined wind turbine foundation has been developed as a design alternative. The result is a foundation that is much smaller in diameter, faster to construct, and much less expensive. Not only does it require a fraction of the materials, but it reduces development, civil work, and O&M costs as well. All in all, these alternative foundation designs represent a savings of anywhere from $250,000 to $400,000 per foundation depending upon site conditions and turbine size.
The P&H foundations use 70 percent less concrete and requires 80 percent less earthwork when excavating. Fewer materials equal less costs, approximately 50 percent less than typical spread foot foundations. P&H foundations are also more efficient to install. Traditional wind foundations can take two weeks for a typical spread foot foundation. However, the time has been minimized to as little as five days for P&H foundations. On a large project, under favorable conditions, contractors have experienced a production rate of as high as the completion of one P&H Tensionless Pier foundation per day. These foundation designs are optimized to incorporate the varying subsurface conditions, considering drainage, grading, and other possible bedrock and geological roadblocks.
The P&H foundations are not only deeper but have key elements which are post-tensioned, reducing the risk of wear, fatigue, and failure from overturning. The deeper design of P&H wind turbine foundation solutions also reduce the risk for seismic hazards and threats related to scour and erosion. The tensionless design of P&H wind turbine foundation virtually eliminates concrete fatigue since the concrete is always under compression. This enables it to potentially handle the loads of larger wind turbines in the future, an option that isn’t viable for spread foot foundations.
Terracon’s P&H foundation systems offer wind turbine foundation design solutions that can extend design life while reducing costs. With more than 8,000 installed foundations globally, (including more than 6,000 installed foundations in the U.S.), representing more than 15,000 megawatts in production, Terracon stands ready to design the foundation. Terracon also provides geotechnical investigations and construction quality control, inspection, testing and observation, and controls risks through certified construction technicians and more than 140 testing laboratories nationwide. Through the implementation of the P&H foundation system, Terracon is ready to handle challenging soil construction and complex construction situations with strategic emphasis on protecting the ecosystem moving into the future.
Mark Underhill, R.G., L.H.G. is Terracon's wind program manager.
Blair Loftis is Terracon's national director, power generation and transmission services.