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

As commercial wind turbine technology has matured, designers have steadily increased turbine and tower sizes in an effort to drive down the cost of energy. Today, that effort has stalled because wind system components are limited by the sizes allowed by transportation. Industry-dominant tubular steel towers have grown so large that their designs are more heavily influenced by delivery and installation concerns than by operational performance. Alternative tower designs - such as cast-in-place concrete or on-site assembled lattices or panels- have been explored, but these are not cost effective compared to existing systems. Keystone eliminates this problem by bringing fabrication to the wind site using spiral welding. Spiral welding is a continuous rolling and welding process that has been used in the pipe and piling industries for more than 50 years. Because it is highly automated and incorporates the entire pipe creation process into a single machine, on-site spiral welding is practical and cost-effective. Keystones innovation adapts this process to the manufacture of wind turbine towers by enabling tapered shapes and variable wall thickness, both requirements for towers. With our system, towers can be manufactured on-site, eliminating transportation barriers and enabling tall, low-cost towers for the wind industry. Keystones process improves the economics of wind energy by both reducing the cost of towers and enabling the wind turbine to reach higher hub heights. Transportation costs are reduced by a factor of ten by eliminating the need for specialized shipping. Larger tower diameters lead to greater structural efficiency, reducing steel usage by 30% for a 120m tower. Hub heights can also be increased by & gt;50%,- increasing wind speed and energy capture by 8-15%-when compared with the 80m towers currently dominating the industry. The added energy capture for these tall towers, along with manufacturing cost reductions, reduces the cost of energy by 5-7% or more. Keystone has worked with experts from the wind and spiral welding industries to prove the commercial and technical viability of our system, and plans to build and test a prototype machine to further prove the technology. During Phase I, we worked with major wind turbine OEMs to develop structural and costing models that confirmed a 50% cost reduction for our technology relative to other 120m towers. We also produced and tested pipes that verified the structural quality of towers produced through spiral welding. Finally, we developed a preliminary machine design that showed that towers meeting the needs of the wind industry can be produced with only small changes to existing, proven spiral mill designs. Phase II will allow us to produce a prototype machine that demonstrates the full automated tapered spiral welding process. It will be used to produce towers for destructive testing, proving the structural performance of spiral welded towers. A residential scale wind turbine will also be erected as a demonstration of the technology. Commercial Applications and Other Benefits: These milestones will prove out the Keystone process, enabling us to attract support from investors and wind turbine manufacturers for the next development phase: construction of a full-scale mobile pilot plant.