Development of On-Site Conical Spiral Welders for Large Wind Turbine Towers

Larger, taller wind turbines could significantly reduce the cost of wind energy and enable much broader deployment, but traditional tower designs cannot cost-effectively scale up due to the size constraints associated with road and rail transportation. Wind turbine towers face a critical bottleneck in the form of the 14-foot diameter limit imposed by over-road transport. With current designs, towers must be highly sub-optimized using many tons of extra steel and incur high shipping and permitting costs to reach even 80-100m heights. Highly desirable taller towers 140m and higher are infeasible with todays steel monopole technology. The grant applicant has developed an innovative advanced manufacturing system that overcomes these transport limits with on-site production of wind turbine towers. Tower production at the wind farm avoids the 14-foot height limit for trucking, allowing structurally optimized steel monopole towers to reach 140m+ hub-heights. This will: Increase the USs available wind resource by 2000 GW, Open large areas of the country to economical power generation from wind, Lower the levelized cost of energy from wind generation, reducing or eliminating the need for subsidies, Shift manufacturing from foreign factories to on-site operations in the US. The applicants manufacturing process is based on spiral welding, a system used for 50+ years to create large diameter welded steel cylinders for pipe and piling applications. Unlike current tower production methods, spiral welding is a continuous, highly automated process that has been demonstrated to be cost effective for on-site production. However, current spiral welding systems are only capable of producing straight pipe, not the tapered, variable wall-thickness structures required for steel monopole wind towers. The applicants innovation enables this with a generalization of the spiral welding process that uses a patented material geometry to wrap constant-width steel sheets into a conical shape without in-plane material deformation. In Phase II, the applicant built and began testing a scaled prototype of a spiral welding system capable of producing wind turbine towers, and also began working with wind turbine OEMs, wind plant developers, wind plant installers, and component certifiers to implement full on-site operation. Proposed Phase IIB work includes construction and testing of critical subsystems at the commercial scale. This work will prove the feasibility of tapered spiral welding for 140m+ towers, and is an essential step toward commercial system implementation.