Meeting future wind generation needs
Demand for carbon fiber, a mainstay of the aerospace industry, is expected to outpace supply within five years, further driving up its cost. ORNL’s more economical formulation could enable the wind industry to afford to compete for the material, said ORNL researcher Subhabrata Saha, who led creation of the blade tip. “It can help match today’s cost while providing higher strength per weight of the blade,” he said.
The hybrid carbon fiber composite blade tip is 41% lighter than a blade tip made with pure glass fibers, Kumar said. “That means we can make bigger blades of the same weight that generate more electricity,” he said.
Doubling the length of a turbine blade allows it to generate four times more power, leading to blades that are sometimes over a football field long. This significant size increase allows for more energy output from modern wind turbines. “But the larger the blade, the larger the chance it will be hit by lightning,” Kumar said.
With so many turbines under construction, it’s urgent to ensure their durability and efficiency with effective lightning protection. “It’s exciting, but more importantly, it’s needed,” Theodore said. “Carbon fiber makes it much easier to extend the length of turbine blades.”
Theodore said ORNL is translating foundational science for commercial application. “We have the whole research supply chain here: We are unique in that we can make the fiber as well as the prototype blade within our ecosystem. That’s what I call quickly scaling up science.”
The blade and a set of smaller composite panels, created simultaneously from the same material, underwent separate tests for voltage and current to simulate lightning’s destructive forces. Current is the rate at which electricity flows, and voltage is essentially the force that drives the electricity between two points. High-voltage tests are used to understand the lightning attachment entry and exit locations, while the resistive heat of high-current tests is more destructive to the composite laminate.
Kumar’s team then utilized ultrasonic imaging to assess any damage to the material. The full wind blade tip emerged pristine from high-voltage bolts of electricity but did not hold up as well to blasts of intense current. However, the prototype sample panels suffered no visible or internal damage and retained their mechanical properties – a technological first that demonstrated “remarkable resilience” to lightning strikes, Kumar said. The same test blasted a hole in a panel made with standard commercial carbon fiber.
What comes next
Why did the ORNL test panels perform better than the full blade tip, despite being made of the same material? One potential cause is that the panels were compression-molded, which created a higher volume of carbon fiber in the composite. They were also heat-cured, a common practice in the wind industry, while the blade tips were allowed to set at room temperature. Heat-curing improves the material by using heat to strengthen its structure and enhance its thermal properties and performance.
But Kumar isn’t counting on an easy solution. Because the resin makes up the largest portion of the blade tip, he wants to experiment with using a more conductive resin.
An affordable, versatile coating can be made from the nanofillers in polymer. Even without the carbon fiber, panels with this coating performed extremely well in recent voltage and current tests, Kumar said.
Kumar explored the economic viability of his research as part of DOE’s 2024 Energy I-Corps program, which helps national laboratory scientists identify pathways for bringing their innovations to market. Through an I-Corps project funded by DOE’s Wind Energy Technologies Office, Kumar interviewed 82 wind industry professionals, including turbine blade manufacturers, wind farm operators and blade repair companies, to learn more about their challenges and what solutions they’d embrace. His nanofiller coating sparked the most interest. Kumar is talking with potential industry partners about field-testing it at a wind farm where its effectiveness can be monitored over time.
Wind farm operators are eager for options, given repair costs for lightning damage range from $10,000 to $100,000 for onshore blades and up to $1 million for replacing a damaged turbine blade off the coast, Kumar said. Insurance companies and equipment manufacturers often decline to cover costs, labeling turbine lightning damage an exempt “Act of God.”
But Kumar is confident: “It’s an act of engineering.”
UT-Battelle manages ORNL for the Department of Energy’s Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science.
This Oak Ridge National Laboratory news article "Thunderstruck: Researchers demonstrate lightning strike protection tech for composites" was originally found on https://www.ornl.gov/news
