That giant wind turbine blade you see is an astounding 88.4m long, or you can say 97 yards if you are a football fan. This blade drives nearly the entire distance of the field in one span. Where will this giant turbine blade go? Certainly not on the land where it will most likely scare the residents silly. No, this blade will be constructed at the French Adwen offshore wind farm where it will power an 8 MW wind turbine. That is enough to power 10,000 homes according to James Billington at the IBTimes.
The technology at the core is by a LM Wind Power who designed the LM 88.4P. According to their website:
“Powering an 8 megawatt wind turbine – the rotor is the ‘motor’ for one of the largest mechanical structures on earth. It has been designed and manufactured with sufficient quality and reliability to withstand 25 years of life offshore, in the harshest weather conditions and roughest seas.”
LM 88.4P Wind Turbine Blade. Image courtesy of LM Wind Power
How does one go about engineering the largest blade in the world? What is crucial is the choice of materials. Glass fiber material is the primary ingredient for the blade’s strength. The blade must be aerodynamically optimized based on expected loading and weather conditions along with physical properties such as length and weight. LM Wind Power tests varying combinations of glass fiber and resin to find the best solution.
There is a gelcoat on the surface of each blade that aids it in resisting salt, sunlight, rain, humidity, and insects. This gelcoat is also non-reflective, so it does not stand out.
The larger blades are also possible due to the SuperRoot by LM which allows for 35-40% more bolts in the root diameter of the wind turbine thereby allowing 20% longer blades.
The turbine blades are tested inside LM’s own wind tunnel using the ISO 9001 and DS/EN ISO/IEC 17025 standards. There is also a static test that lasts for a week by using a traction rig to create the max load at the leading edge, trailing edge, suction side, and pressure side. The picture below shows where these are at on your typical wind turbine blade.
The airfoil of a wind turbine. Image courtesy of Google.
Then a dynamic test follows using an infrared camera to detect cracks to a blade when being fatigued like it would if it was running for 20 years. This is done both edge wise and flap wise on the blade. These directions are shown in the picture below as well. Following this another static test is done to make sure the blade holds up even after aging.
The edge wise and flap wise directions. Image courtesy of National Instruments.
This is a promising step for offshore wind which is finding interest from a host of nations including Germany and Denmark. In fact, the United States and Denmark have inked a Memorandum of Understanding (MOU) to develop offshore wind energy. By being able to design such large structures, not only do economies of scale come into play where the energy is cheaper due to its larger size. There’s also the scientific mastery of using the proper materials and geometry to design wind turbines which brings the industry closer to maturity and technical proficiency. For offshore wind to truly take off, reliable transmission lines must be set up to bring the energy back to shore at a high enough voltage for the grid.