How wind turbines work and the big challenges of manufacturing them
Posted by Bert Maes on February 9, 2010
A summary of Assembly Magazine’s cover article “Assemblers Harness Wind Power“, by Austin Weber, January 27th 2010.
Wind power is the cheapest and most popular type of regenerative energy. As a result, manufacturers all over the world are scrambling to build gearboxes, generators, blades, power systems, motors, control systems and other types of electromechanical devices.
How does a wind turbine work?
Wind power works by harnessing the breeze that passes over the rotor blades of a wind turbine and rotates a hub. The hub is connected to a gearbox via low-speed and high-speed shafts that drive a generator contained within a nacelle. A generator converts the energy into electricity and then transmits it to a power grid.
The typical wind turbine is a slender structure that consists of a three-bladed rotor that extends up to 300 feet in diameter attached to the top of tall towers that soar hundreds of feet into the air. A yaw mechanism uses electrical motors to turn the nacelle with the rotor against the wind. An electronic controller senses the wind direction using a wind vane.
How is a wind turbine made?
The average wind turbine contains up to 8,000 parts that must be assembled. Towers and rotors are the largest and most basic components.
Most wind turbines are designed for a 20-year life cycle. The gearbox and drivetrain system must be strong enough to handle frequent changes in torque caused by changes in wind speed. Bearings are extremely critical. The whole system must be correctly aligned to minimize wear from vibration and any resulting noise.
One thing that differentiates wind turbine manufacturing from other industries is sheer size. All components, such as bearings, gears and generators, must be extra large and extra strong. Big parts and big plants are common in the industry. For instance, the typical gearbox weighs around 30,000 pounds.
Due to their size and weight, gearboxes are often moved through assembly steps at plants in Germany using large rail systems similar to those in automotive plants. Quality expectations in the industry are huge, because manufacturers demand reliability and low maintenance. Wind turbines don’t make money if they’re not working.
Towers typically consist of large tubular structures. Plated steel sheets are rolled into rings and joined together with submerged arc welding. The tower sections are typically fabricated into cans about 20 meter long and then bolted together through internal flanges. This is an industry that needs to build large, high-capital items in a production line manner. It may be compared to aerospace.
There is great potential for advanced robotic welding to be developed. On the other hand, rotor blade manufacturing from fiberglass and other composite materials tends to be the most innovative and highly secretive area of the wind turbine industry. Blades over 70 meters long are now being designed. To achieve low-cost mass production, automated solutions from aerospace or automotive, such as robotic tape layers, have to be used to join long lengths of blade to assure aerodynamic conformance.
What are the challenges facing manufacturing wind turbines?
Wind technology will need to evolve. Engineers need to make wind turbines larger, taller, less expensive, more reliable and more efficient. Because wind turbine components undergo excessive forces and a tremendous amount of joint stresses and failures, numerous manufacturing issues must be addressed.
It looks very graceful and simple, but the aerodynamics, power characteristics, vibrations, system fatigue, acoustics of a wind turbine are harder to understand than an airplane or a helicopter.
For instance, blades, towers and casings must be able to withstand heat, cold, rain, ice and abuse from changing wind speeds. Blades must also be built with a high strength-to-weight ratio, so research into new materials is key.
Making wind energy practical is a matter of maximizing efficiency and minimizing production cost.
Reliability is critical in the wind turbine industry. The most difficult application is the gearbox, because it is important to avoid any distortion. The challenge is to maintain clamp loads for the service life of the turbine. Manufacturers are looking at weight reduction and improved assembly of threaded joints.”
Close tolerances, the ability of components to withstand operation in difficult conditions, and the availability of quality materials are all important challenges facing engineers. It is also a challenge to develop parts that are light-weight enough so that the final system can be assembled more easily, but they must also be durable enough to withstand difficult operating conditions.
And finally: the industry is struggling to build a local supply chain. The availability of a steady and sufficient supply of locally sourced components is important, as turbine companies increasingly develop production facilities away from their home base, they need to be able to have access to enough quality components to build the systems at their new location.”
Feel free to also read:
- Green Technology ~ Wind Turbines and CNC
- Green Technology ~ Nano-engineering and CNC
- Green Technology ~ Solar Power and CNC
- Robotics in manufacturing