Wind Turbine Blades of Carbon and Glass Fibre

There are many sources of renewable or ‘green’ energy that we use to generate electricity including wind, tidal, and solar. Wind energy is one of the oldest, if not the oldest natural energy source that we have learned to harness. Earlier days saw wind being used to power ships and grain mills; today we see wind being used to power almost anything that requires electricity. The increased demand to utilize renewable resources has led to a surge in the installation of wind farms, with large tracts of land and coastal areas devoted to the operation of wind turbines. Competition within the industry has grown as manufacturers strive to build longer and more efficient blades. Advanced composite materials are a growing part of the construction of wind turbines, specifically the blades. With high demands for certain characteristics, manufacturers decide what materials and processes will perform the best in order to accommodate these requirements.

In the effort of converting wind into usable, storable energy, we have discovered that the longer the blades are on a turbine, the more energy can be generated. Increasing the blade length, however, is easier said than done with consideration to mass and inertia, material strength, weight, and rigidity. It is for this reason, among others, that glass and carbon fibres are most commonly used in the fabrication of wind turbine blades today.

With these elements in mind, there are several pros and cons in the use of glass and carbon fibres:

Glass Fibre

Glass fibre has proven to be one of the most versatile materials to use in the composites world. The ability to mold glass fibre into complex shapes ultimately allows the blade manufacturer numerous solutions to any particular problem. Glass fibre is manufactured in bulk and large quantities of glass fibre can be produced from a very small amount of glass. Consider an average sized glass marble; 90 miles of glass fibre can be produced from that singular marble. For this reason, glass is an extremely inexpensive material to use, especially when compared to other popular-use composite materials such as carbon or aramid fibres. This is a driving factor in the widespread use of glass fibre. Several additives and minerals can be incorporated to alter the chemical and physical properties of the glass which, in turn, has a hand in dictating its cost. Using a lightweight material is critical for turbine blade construction since they need to be exceptionally large yet maintain the ability to be transported and positioned on the tower. Though the use of this lightweight material is prevalent in blade construction, it does not mean that these blades are, in fact, lightweight. A large blade mass is necessary to the operation of a turbine; without it, there would be little momentum to keep the turbines running when the wind dies down. Some of these blades easily exceed 100 000 lbs!

Additionally, glass fibre does not corrode as metals do, therefore it requires less maintenance and is an overall more cost-effective solution. These are significant advantages for a wind turbine to have since they are constantly exposed to the elements, both on land and at sea. Blade design and manufacturing methods strive to optimize performance and cost effectiveness. Certain ‘Low-Tech’ methods can lead to numerous defects such as delamination, disbonding, excessive resin content and skewed fibres in the blades that may require post-manufacturing repairs.

Carbon Fibre

Carbon fibre is well known for its tensile and compression strength, low weight, and resistance to corrosion. Carbon has immense tensile and compression load capability, so it is often placed within a typical turbine blade as the ‘spar’, the primary load bearing component of a blade. Unfortunately, due to the complexities in manufacturing carbon fibre, it is also a very expensive material.

To a much greater extent than glass fibre carbon ‘fails catastrophically,’ which means that it does not elongate or deform under stress/ strain, or upon impact. It’s yield strength is so close to it’s ultimate strength that the moment it begins to elongate, it ruptures / fractures instantly. This makes inspection and repair to these blades imperative so as to find any defect that could compromise the structure.

There are many benefits in the use of glass and carbon materials but overall, it depends on what the design is calling for. Another valuable benefit these two materials share is their ability to be repaired ‘on-tower’ or ‘in field’(provided a trained technician is available). Blade repair is a specialized industry with Technicians who have a very specialized skill set. Turbine maintenance and repair companies are desperate for workers who are trained in maintenance and repair in this technology. Which makes it a very viable career choice for those seeking post-graduate employment and second career opportunities. Wind energy is evolving fast, increasing wind turbine demands with no shortage of technical positions to be filled for their construction and care.

For more information about available training for Wind Turbine Blade Repair and active employers in the Wind Energy industry, visit ACT’s website at www.advancedcompositestraining.ca.