1. Field of the Invention
The present invention relates to wind turbine blades and methods of manufacture for wind turbine blades.
2. Description of the Related Art
The current approach to manufacturing wind turbine blades is to produce each blade either as two half shells and a spar, or as two half shells with an integral spar. In both cases, the two half shells are bonded together along their edges to form the complete blade.
The blades are typically made from fibre reinforced plastic using either resin infusion or prepreg techniques. In both cases, the blades are produced in large labour and capital intensive facilities and then transported to the location of the wind turbine or wind farm.
The shortcomings of the current approach are primarily related to scale, wind turbine blades typically being 40 m in length or more. As the size of the blades increase, so does the associated cost and probability of manufacturing defects, as large, high quality, components are notoriously difficult to manufacture. Furthermore, as the blades get larger, it becomes more difficult to control the tolerances of the two half shells thereby making it difficult to register the edges of the two half shells in order to join them together.
In use, larger blades are more desirable than smaller blades since they trace a larger envelope and therefore capture a greater proportion of the available wind energy. This means that fewer wind turbines are needed for the same power generation capability.
Notwithstanding the above, the larger the blades are, the more difficult and expensive they become to transport. This is aggravated by the fact that many wind turbines are located in hilly areas which may be inaccessible by road. Occasionally, blades are cut in half to reduce the overall length of the structure to be transported, a field join being made later at the site of the wind turbine. However, this is not a satisfactory solution, involving as it does, the cutting in half of an otherwise structurally sound and expensive component.
Thus it can be seen that, in practice, the size of wind turbine blades produced by conventional techniques are limited by the cost and difficulty of manufacture and also, the cost and difficulty of transport.