Offshore Wind Blade Not Too Large To Fail

Offshore Wind Blades Testing And Certification

Not too big to fail

Climate activists have renewable energy goals to be met by 2025 and 2030. The main goal is carbon neutrality by 2050.

The world's biggest companies, investors, cities, and regions have combined forces to push local and state governments to increase their 2025 climate goals. The pressure is on and big mistakes can happen.

To reach these renewable goals fossil fuel plants are shut down with massive ocean wind projects taking up the slack. The bigger the megawatt wind turbine the more chance of attaining the renewable energy goals. The newly installed ocean turbines are over 800 feet tall with 350-foot blades.

Tests in 2022 were conducted in Massachusetts to test a prototype 350-foot wind turbine blade before producing 150 blades in Canada for the ongoing ocean project today.

There was nowhere in the world available to test a 350-foot blade. The Massachusetts site could only test a blade up to 300 feet. To test the prototype blade they had to cut more than 50 feet off the blade and more than likely place weight on the cut-off end to make up for the missing blade section.

Engineers have to extrapolate the figures from the 300-foot section to the 350-foot section. The blade made it through the tests and was certified.

Several of these 350-foot blades in service have failed off Nantucket and Europe.
These blades are so large, they oscillate in the wind. The tips of the blades travel around in a circle over 700 feet wide. The wind speeds at the top are much higher than at the bottom. The result is constantly varying speeds.

The result of a blade break around 50 feet from the rotor or center of the turbine could be what is called classic torsional fatigue.

These 350-foot large blades are made in a fiberglass shell and lack expensive reinforcing carbon fiber. At least one blade should have been tested in a NASA wind tunnel before mass production.
In 1997 there was a warning from LM Glasfiber of Denmark, following several instances of stress cracks appearing on blades subjected to violent edgewise oscillation.

The damage from edgewise oscillation has amounted to serious longitudinal cracks on the trailing edge of the blade several yards from the root. The root is the structure holding the outer part of the blade to the rotor or center

One blade before 1997 oscillated so much it hit the tower causing the blade to break and fall to the ground. The cure was to install vibration detectors to avoid acute blade damage.

The oscillation problem has been known for more than 25 years. It occurs on all wind turbine blades but increases with their length and weight.

The oscillation can start with blade stiffness, temperature, and wind gusts. Why install the new 13-megawatt ocean wind turbines without the vibration detectors?

The 350-foot blades required a lot of financing, but they are so big that they may fail without carbon fiber reinforcing.

Note# For years the wind industry denied wind turbine infra-sound. The US Dept of Energy was aware of the infra-sound from a Mod 1 wind turbine in Boone, North Carolina in 1985.

# Note: Massachusetts is testing 350-foot blades in the 300-foot test site. Removed more than fifty feet off the blade to test inside the test site: Extrapolation used to compare test results

Massachusetts 300-foot test site