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Mr. Sebastian Webel
Mr. Sebastian Webel

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Pictures of the Future
The Magazine for Research and Innovation
 

Sustainable Power Generation

A New Spin on Production

Siemens is developing new concepts for the production, transport, and assembly of its wind power systems.

Electricity generated from wind is still generally more expensive than power produced from coal. Siemens Wind Power plans to introduce industrial manufacturing processes across the board in order to make wind power more competitive and accelerate growth. Tips can be learned from car and truck manufacturing.

Siemens Wind Power has set itself a clear goal: to lower the cost of generating one Kilowatt-hour (kWh) of onshore wind power to less than five euro cents by the end of the decade. That would put wind power on a par with traditional energy sources. By comparison, a kilowatt-hour of wind power now costs around seven cents, depending on the location in question. Siemens also believes the price of electricity produced by offshore facilities needs to be substantially reduced, since it’s currently around twice as high as the onshore price. The company’s target is therefore to lower the price to less than ten cents per kWh, which would make offshore wind power competitive.

As it increasingly focuses on competitiveness,  the wind industry can learn from car and truck manufacturing. Over the last few decades, the auto industry has optimized vehicle components to such an extent that they can now be manufactured as cheaply as possible. Much of this success can be attributed to platform strategies, modularization, standardization, and lean manufacturing processes.

By adapting some of these approaches to the  production of giant rotor blades for wind turbines the wind energy sector could become more efficient and learn from the automotive industry.

Seamless Blades

Siemens is the only company that manufacturers blades that are up to 75 meters long as a single component. The rotor blades have no seams, which means there are no weak points. As a result, they can reliably resist wind and weather for at least 20 years. However, rotor blade production is a very labor-intensive and drawn out process. Working in a 250-meter-long production hall in Aalborg, Denmark, Siemens employees currently lay out rotor blade molds with glass fiber mats and balsa wood by hand before the upper and lower halves are joined, evacuated, and filled with liquid epoxy resin.

Automated blade production could save 30 million Euros per year in production costs.

Robots could lay out the molds just as well as humans. They’d also be much faster. They could run along the mold fully automatically and finish three meters each second. That would halve production time from 300 hours to 150 – and cut manufacturing costs by €30 million a year.

Initial tests with a mold for a 40-meter-long rotor blade produced positive results, and plans now call for the first 55-meter-long blades to be manufactured with the help of robots in Aalborg as early as 2014. “We will use conventional industrial robots that will be specially programmed by our rotor blade production experts,” says Jan Rabe, Chief Strategist at Siemens Wind Power. “This will put us well ahead of the competition.”

But that will only be the first step. Siemens itself could also manufacture the made-to-measure mats for blade production directly from fiberglass in order to satisfy the special requirements associated with windmills. “Mats can be woven with varying thicknesses in accordance with their position in the rotor blade,” says Rabe. “If we were to take that into account during the manufacturing process, we could reduce the costs of the blades even further.”

Rapid Growth

Such approaches will be needed if the wind power sector is to continue the substantial growth it has achieved over the last few years. Sales at Siemens Wind Power alone have increased by around 40 percent each year since 2004, when Siemens acquired Bonus, a Danish manufacturer. At that time, Bonus was building approximately 200 wind turbines per year and posting annual sales of €300 million. Today, Siemens builds some 2,000 turbines each year and generates sales of €5 billion. The order volume currently stands at €11 billion. The industry has entered a consolidation phase and needs to increase productivity and reduce costs.

This also applies to the production of wind power plant nacelles, which account for roughly 60 percent of manufacturing costs. The remainder is more or less equally divided between the tower and the rotor blades.

All in all, Siemens Wind Power is relying on modularization and reduced complexity to reduce costs. For instance, its new three-megawatt and six-megawatt turbines forego the usual combination of a gearbox and asynchronous generator. Instead, they use a directly driven synchronous generator equipped with permanent magnets and a corresponding conversion-to-grid frequency. This gearless direct drive concept eliminates 50 percent of the components normally used in such systems and reduces the unit’s weight by 30 percent.

Wind turbines also include modules such as, for example, hydraulic and power electronics systems that can be used in other products as well. Many module components – such as the electric motors for aligning the turbines – can thus be installed in various types of wind turbines. This lowers procurement and warehousing costs.

Lowering Transportation Costs through Modular Production

Customers not only benefit from the lower capital expenditure required for every megawatt of installed capacity; they also save money on maintenance. “ Siemens’ gearless design increases turbine reliability and by dong so lowers maintenance costs during operation,” says Rabe. “This is important because repairing a damaged gearbox offshore costs almost as much as installing the original turbine.” Most of the wind power plants that Siemens sells in Europe already use direct drive technology, which Rabe expects to account for the lion’s share of the portfolio in just a few years.

By then, it’s likely that the basic design of the nacelles will also change. Today, these components are still assembled at three plants: Brande, Denmark; Hutchinson, Kansas; and Shanghai, China. After assembly, they are transported to find farms around the world.

Modularization can significantly simplify logistics.

But in the future, engineers plan to divide these complex system into two modules – the generator in front and the tail end, which holds the power electronics and the actuator for the nacelle. The idea is that the two modules should remain separated until they arrive at the top of the wind turbine tower. This approach would make production much more flexible. “Such modularization would enable us to manufacture the tail end at other locations around the world,” says Rabe. “However, the complex generator module would continue to be manufactured at only a few locations by Siemens, in much the same way that automakers build engines at their own centralized plants but have modules such as vehicle cockpits delivered.”

The cost of transporting these so-called split nacelles to construction sites would also be significantly lower. After all, depending on the country in question, it can make a big difference whether nearly 80 tons of cargo is shipped as a single package or in two separate, lighter loads along narrow roads and across fragile bridges.

Siemens’ innovative approach will soon simplify transport of the towers as well. Most towers still consist of large and heavy steel segments with a diameter of up to six meters. These have to be stacked and joined at the construction site.

Siemens Wind Power has simplified and standardized its entire product portfolio in this manner. More specifically, it has reduced what used to be 13 product lines to just four platforms. Customers can thus choose between two turbines with 2.3 or three megawatts and two larger units with four or six megawatts. Each of the four platforms in turn consists of six modules: the rotor blades, the gearbox or the segment linking them to the generator, the generator itself, the tail end, the tower, and the electronics needed to generate the grid frequency. Each of these modules is, in turn,  made up of sub-modules. With so much modularization taking place, it appears that the automotive industry’s platform strategy has been successfully transplanted to the wind power sector.

Christian Buck