Keystone Tower Systems, Inc. — Department of Energy SBIR Phase I: Large-scale wind turbine designs are significantly constrained by transportation limits. A

Description

Large-scale wind turbine designs are significantly constrained by transportation limits. As utility scale wind turbines have developed, they have steadily increased in size and have seen a steady decrease in cost of energy. However, further increases in on-shore turbine size beyond 3MW are prohibited by hard limits in the size of components that can be economically transported to the wind farm site. The wind turbine tower is one of the components that are constrained by transportation limits. Steel monopole towers for wind turbines have been found to be technically and economically superior to competing designs (i.e., fully concrete or steel/concrete hybrids) but cannot be transported on-road for turbines larger than 3MW. In addition, steel monopoles in the 1.5-3MW range are non-optimally designed due to transportation constraints, and must use significantly more steel than optimal in order to stay within a 4.3m diameter transportation limit. Conispire has developed a technique to eliminate this transport barrier and enable use of large diameter, weight-optimized towers through on-site production. We have identified and proven (using a small-scale prototype) a geometrical construction that enables on-site construction of tapered steel monopoles using spiral welding. Spiral welding is a proven technology widely used for on-site manufacture of large diameter steel tubes for the pipeline industry. On-site production allows large diameter towers to be constructed, achieving weight reductions of 40% or more for turbines in the 2-3MW range, and enabling low cost steel monopoles to be used for turbines over 3MW. Transportation costs are also significantly reduced as materials can be shipped as hot rolled coil stock using standard flat bed trucks rather than the expensive specialty shipping methods currently required. These savings add up to a roughly 5% reduction in cost of energy with existing turbines and hub-heights, and significantly more as designs shift to larger turbines and higher hub heights