Sandia’s Wind Energy and Electrical Sciences researchers, in collaboration with Wetzel Wind Energy Services and Stratasys Direct Inc., have designed a new turbine blade tip that promises to make wind energy production more efficient.
The team recently completed the modeling and design phase of the Additively Manufactured System Integrated Tip project to develop a 3D-printed wind turbine blade tip that integrates several technologies and demonstrates a path to improved performance and reduced levelized cost of electricity, a measure of the cost of electricity generation over the lifetime of the wind turbine.
Funded by the U.S. Department of Energy’s Advanced Materials and Manufacturing Technologies Office, the AMSIT project sought to address a number of current manufacturing inefficiencies, including manual composite-fiber-epoxy layup processes; poor quality control in manufacturing leading to blade defects and failures in the field; erosion damage, especially at the tip; damage due to lightning strikes requiring extensive repairs or complete blade replacement; and expensive and complex shipping logistics due to the size of modern blades.
“3D printing offers a path to address all of these issues by integrating technologies,” said Brent Houchens, AMSIT’s principal investigator. “Here we considered a winglet to increase lift, surface texturing to reduce flow separation and features to improve leading-edge erosion protection and lightning protection.”
“Although significant challenges remain in terms of the material properties and speed at which large parts can be 3D printed,” Brent added, “strength and surface quality are advancing rapidly, and modular additively manufactured designs could reduce shipping and logistics issues, reducing emissions and securing supply chains. This is the first step to a future where blades can be manufactured in the field, on demand.”
The additively manufactured design integration was demonstrated for a 200 kilowatt-scale turbine with 13-meter blades, while also examining the potential impacts for megawatt-scale machines. Approximately 15% of the blade tip was replaced with a 3D-printed design that improves aerodynamic performance via an upwind winglet and surface texturing, while simultaneously reducing repair costs through integrated leading-edge erosion and lightning protection. The team was able to explore highly complex geometries that would be challenging for traditional manufacturing processes but are straightforward for 3D printing. The potential for fast tip replacement — for example, after a catastrophic lightning strike — takes advantage of the modularity of the design.
Modeling results
Models predicted the change in levelized cost of electricity over a 25-year turbine lifetime, with performance improvements allowed only at low- and mid-wind speeds below 10 meters per second — the maximum rated power of the turbines were not changed so that AMSIT blades could be tested on existing machines. Even in this highly constrained design, techno-economic analysis demonstrated that when all four technologies are combined, levelized cost of electricity decreases significantly, between 3%-4% on average at wind speeds below 10 meters per second for a fixed print resolution, far offsetting the increased costs of 3D printing the tips.
Even more significant gains could be realized by increasing the rated power. At kilowatt scale, the winglet had the most impact by increasing the annual energy production at wind speeds considered. At megawatt scale (a megawatt is 1,000 kilowatts), performance increases and reduced maintenance and repair costs associated with erosion and lightning all contributed significantly to reduced levelized cost of electricity. As costs of 3D printing continue to decrease, the levelized cost of electricity from a design like AMSIT will continue to decrease.
Experiments and fieldwork
AMSIT researchers also conducted laboratory experiments to ensure the survivability of the 3D-printed materials against lightning strikes. Three lightning test scenarios included a strike directly at a simulated lightning protection system, a surface strike away from the lightning protection system and a strike with no lightning protection system.
Laser scans provided accurate blade geometries to mate the 3D prints to the existing blades. The outer shell of the blades were then cut away from the internal structure so that the new tips and winglets could be attached for ground-based structural tests and then field demonstration at the Sandia Scaled Wind Farm Technology site in Lubbock, Texas. These tests will help assess the progress of additive manufacturing toward the goal of 3D printing large sections of wind turbine blades and eventually even full blades.
“The AMSIT project demonstrates how integrating technologies through 3D printing could reduce the cost of wind energy by improving aerodynamic performance and reducing repair costs,” Brent said. “Upon completion of the project the modified blade root and stub will be available for testing other novel tip designs.”
To learn more about AMSIT, contact Brent C. Houchens.