This Small Business Innovation Research (SBIR) Phase I project addresses two roadblocks to reducing the cost of wind energy: the labor-intensive construction process, and size limitations imposed by road or rail transport for turbine components. The former issue drives up manufacturing costs and reduces US competitiveness with countries with inexpensive labor, while the latter forces sub-optimized tower designs and prevents turbines from growing larger and taking advantage of faster, steadier winds at higher hub heights. This project addresses both of these problems by adapting spiral welding - a well understood system for pipe and piling manufacturing - to wind tower production. Spiral welding is highly automated, requiring as little as 10% of the labor of the equivalent manual process. It also combines multiple operations into a single machine that can be operated on-site, eliminating transport costs and barriers. This project's innovation is to adapt existing spiral welders - which can manufacture only straight, constant wall-thickness pipe - to producing tapered, variable wall thickness towers. A novel material geometry and automated control of machine parameters are the keys to transforming the standard system to one optimized for turbine tower production. With on-site spiral welding of turbine towers, significant reductions in cost of wind energy are possible.
The broader impact/commercial potential of this project will be felt in many areas: technical, commercial and environmental. The system?s major contribution is an increase in the use of wind energy for US electricity, enabled by both reduction in energy cost and increase in the number of cost effective wind sites. Reducing the cost of tall towers enables increases in the height and size of wind turbines, allowing them to reach and be optimized for steadier, higher speed winds. With these increase in size and optimization, decreases in cost of wind energy of 12% (for 120m tall towers) or more are possible. In addition, the US land area for which wind energy is cost effective can be doubled at 120m hub heights. Spiral-welding of turbine towers also provides US jobs and increases American competitiveness with overseas producers. Because on-site production is inherently local, manufacturing jobs are created in the communities where wind turbines are installed. Also, this method gives local production a major cost advantage over imports by producing towers that are too large to transport from port to wind farm. This allows domestic manufacturing to not only compete, but dominate in a domestic tower market worth roughly $1B in 2011.
Keystone Tower Systems’ advanced manufacturing technique for wind turbine towers will bring low cost wind energy to many regions that cannot currently access it, while creating much needed domestic manufacturing and construction jobs. Today, wind energy is only cost effective in plains states where the lack of tree cover allows strong winds to reach close to the ground. In order to bring wind energy to areas with trees, towers that are >120m tall are needed. Creating towers this tall would ideally involve constructing towers that are >20feet in diameter, far larger than the 14 foot diameter limit imposed by over-road transport limits (due to overpasses, power lines, etc.). Keystone’s on-site manufacturing process frees towers from this transport limit, enabling steel to be transported as flat sheets, and rolled and welded into the tower at the wind farm. Increasing hub-heights from today’s 80m to 140m nearly doubles the developable wind resource in the US, and brings low cost wind to many states in the east, south, and west that currently lack a wind industry. Also, with towers too large to transport, domestic manufacturers are given a fundamental advantage over foreign factories in a domestic tower industry worth $1B today, and more with an expanded market from taller towers. This NSF SBIR project played a critical role in advancing Keystone’s tapered spiral welding process towards commercial production. The wind industry places very exacting buckling and fatigue requirements on wind turbine towers. Buckling and fatigue are both strongly influenced by minor imperfections that result from variation in the raw materials and manufacturing process. This SBIR project helped model and characterize this variability, and identify which aspects are most critical for meeting the structural requirements of wind turbine towers. Moving forward, this research will help to optimize the manufacturing process and prove that spiral welding can meet the structural needs of wind turbine towers, while freeing them from the diameter constraints that are currently holding back the wind industry.
