SIEMENS

There’s something special about the 62 wind turbines whose rotors turn tirelessly at West Wind Farm, located 15 kilometers west of New Zealand’s capital, Wellington. For one thing, they’ve traveled around the world to get here from Brande, Denmark — a distance of roughly 20,000 kilometers. Each of the 62 turbines has an output of 2.3 megawatts, which adds up to a total of 140 megawatts, enough to supply electricity to 70,000 homes. What’s more, West Wind Farm produces its electricity for the same price as a coal-fired power plant.

One reason for the competitive price of this energy is the powerful, even wind that blows through the Wellington region; another is the fact that the wind turbines are high-tech units from Siemens whose development required a huge amount of skill and engineering expertise. It all starts with the fiberglass rotor blades, which were built as a single unit without any welding whatsoever. This makes them very robust, as there are no weak points where the blades can break. Sensors installed in the hub and nacelle also permanently monitor operating parameters and sound an alarm if suspicious deviations are detected. Like all Siemens facilities, the wind turbines at West Wind Farm are designed to operate for 20 years and therefore have to be able to withstand hundreds of millions of rotations.

Wind power is one of the most promising renewable energy sources today. Wind turbines already supply ten percent of the electricity generated in Germany; in Denmark, the “birthplace” of wind power, they account for almost 25 percent of the electricity produced, and China — now the world’s biggest market for wind power facilities — is a major customer. Worldwide installed wind power output is currently just under 200 gigawatts, and this figure is doubling every three years. The European Commission estimates that by 2030 up to 135 gigawatts could be installed in European coastal waters alone. That’s almost as much as the installed output of all the power plants in Germany, which totals 170 gigawatts. The Commission believes the share of power output in Europe accounted for by wind facilities could increase tenfold, from five to 50 percent, by 2050. The European Wind Energy Association (EWEA) estimates that annual investment in wind power in the EU will double to €26 billion by 2020. That doesn’t mean we’ll be seeing wind farms everywhere, however, as a large portion of this investment will flow into re-powering — i.e. replacing older units with new and more powerful turbines.

High Tech in the Countryside. Denmark is home to one of the global centers for wind power. Brande is a small town that at first glance looks like a quiet, idyllic hamlet in the midst of a hilly landscape nestled between the North and Baltic Seas. At the edge of town, however, is a Siemens facility that has several thousand employees, including around 500 engineers who develop new solutions for making wind turbines more efficient and thus cheaper. One of these engineers is Per Egedal, 36, who was named Inventor of the Year 2011 by Siemens. Thanks to Egedal’s work, Siemens Wind Power turbines are now among the world’s most efficient — and efficiency is the key to competitiveness. After all, if a turbine’s energy yield rises by one percent, for example, the price for a kilowatt-hour of electricity falls by one percent. A lot still needs to be done, however, because a kilowatt-hour of wind power currently costs five to seven euro cents on land and 15 cents offshore, due to the higher installation and maintenance costs. “We need to get down to four to five cents per kilowatt-hour if we’re to compete with coal on a global scale,” says HenrikStiesdal, Chief Technology Officer at Siemens Wind Power. Stiesdal has no doubts that this is possible — for one thing, because of the inventions made by his colleague Per Egedal.

One of Egedal’s creations is a software program for regulating wind force on a turbine so that the unit can operate absolutely undamaged throughout its service life of 20 years. Despite what lay people might think, a rotor should not always turn at full speed, as this causes its components to wear out more quickly than they’re supposed to. That’s why Siemens wind power units have sensors mounted on their hubs that monitor blade loads. Egedal’s software uses these measurements to determine the stress load the unit is exposed to at any given time and compare that value with an ideal stress profile. Depending on the degree of deviation, the software might temporarily cut back the unit’s output. “It’s more important for operators that a wind turbine supplies electricity for as long as possible rather than always generating as much electricity as possible — even when conditions are tough,” says Egedal.

Optimal calibration of the rotor blades also lowers stress on the tower, which means the tower’s steel walls can be made thinner — and “that will quickly reduce the amount of material you need by several percent and thus cut costs,” says Egedal. These savings can be considerable, given that some wind turbines are now as much as a hundred meters in height.

Egedal has also developed a monitoring program that identifies rotor blade damage at an early stage by using sensors to measure vibration frequencies inside the nacelle. The frequency patterns provide information about the condition of the blades. The software sounds an alarm if a change in the frequency pattern is detected. Technicians can then decide whether repair work is necessary and, if so, what needs to be fixed before other components are damaged. Repairs must be carried out as quickly as possible because the rotors shouldn’t be shut down for too long.

Siemens turbines are monitored by Siemens’ three worldwide wind power control centers, which are located in Brande; Bremen, Germany; and Newcastle, U.K. The control centers also manage software installations and updates, which can be sent through the Internet to any of 4,000 monitored turbines.

“Many small steps need to be taken to make wind power competitive,” says Stiesdal. “Our innovations cover the whole value chain, from manufacturing to maintenance.” In the future, for example, individual filaments instead of fiberglass mats will be used for molding rotor blades. That makes sense, because it’s very time-consuming and expensive to weave the mats, which are produced by various companies in Europe, the U.S., and China. Siemens has already built a 45-meter-long prototype using the filament technique. Plans call for the technology to be gradually introduced at the end of 2012, with large-scale production scheduled to begin in 2014. “This and other process optimization measures that are in the pipeline will cut the cost of rotor blade production in half,” says Stiesdal.

Less Is More. Gearless wind turbines are another innovation created in Brande. Conventional wind power units have a gearbox and a generator that turns quickly — but both can be replaced with a slowly rotating, high-torque synchronous generator. The resulting gearless turbines have only half as many parts as normal turbines. This simplifies maintenance and substantially reduces the unit’s weight. This approach saves Siemens and its customers money on replacements, because the machines are more reliable. For example, the gearless 6-MW turbine introduced in 2010 is more than ten tons lighter than a conventional 2.3 MW unit. This weight reduction is particularly important for offshore wind facilities because their installation costs are very high and they are difficult to access for repairs.

A Type B52 rotor blade lies outside on the extensive grounds between the production halls and the engineering offices in Brande. The blade is a pristine white and 52 meters long, with an elegant shape that resembles a thin whale. “Our rotor blades are the world’s biggest fiberglass structures built as single components,” Egedal says proudly. Their production process is something like baking a cake in a sandbox. First, fiberglass is placed into two molds, both of which are folded together, evacuated, filled with resin, and heated. The fiberglass is baked into a rotor blade within 24 hours. Experts then glue small plastic teeth that look like dragon scales along the blades. These ensure that air is pressed onto the rotor blade more strongly — another small detail that improves efficiency by two to three percent.

Production of the 2.3-megawatt generators, which are especially in demand, is also being optimized. An LED display hangs suspended in the large hall where the nacelles for these units are manufactured. The display is actually a clock that reads 1:44 at the moment and counts downwards. It tells workers that the current manufacturing step must be completed in this time. In other words, everything here is clocked like in a car factory. Each production step takes two hours; after that the component rolls to the next station. It takes eight stations to fit the nacelle shell with its interior components, including the gearbox, generator, hydraulic system, computer, measuring instruments, and doors. The entire process results in a finished nacelle with a protruding hub for the rotor blades.

This new system has cut the time it takes to complete a single unit from 36 hours in 2010 to just 19 hours today, which saves a lot of money. Siemens’ success shows it’s on the right track. Around 800 people were employed in Brande just under ten years ago; today there are 3,200. The facility used to manufacture turbines with a combined output of 450 megawatts each year; now it builds units with a total output of roughly 4,000 megawatts. All of this has increased the company’s demand for space, which is why a new manufacturing hall for 2.3 MW nacelles is now being built. “There’s always some kind of production building going up around here,” says Egedal.

Wind Power employees are busy putting wind turbine components through endurance and other tests. Rotor blades, for example, are made to rock back and forth on a special crane for three months without stopping — that’s about two million oscillations. This is how Siemens simulates 20 years or so of operation to test material durability.

Another innovation developed by Stiesdal’s team was also tested here: the “Arabian scimitar,” which is viewed as the rotor blade of the future. The blade is slightly curved and twists under the force of the wind, which reduces load. Known as “aeroelastic tailored blade” technology (ATB), this new concept is especially useful on the high seas, where air masses of up to 100 tons per second strike the blades, often from different directions. Elastic blades can adapt to the wind flexibly. And because blade material is subject to less wear and tear, its service life increases. The new blade form and its improved stability make it possible to produce longer rotors that generate more energy without an increase in aerodynamic load. Indeed, the new blades are 53 meters long, or four meters longer than their predecessors. “Although the blades are 500 kilograms lighter,” says Stiesdal, “they have a five percent higher energy yield.”

Siemens has other innovations in the pipeline as well. Egedal, the software inventor, has also developed a program that regulates the load on each rotor in a wind farm in a manner that optimizes overall performance. Wind farms where rotors are placed only a short distance apart tend to experience significant losses due to wakes behind the turbine rotors. “In such a situation, it makes sense to cut back somewhat on the power output of the first and second turbines in a row,” Egedal explains.

Powerful Future. Bigger, lighter, and more powerful — there’s still plenty of room to further optimize wind turbines. A prototype of the six-megawatt unit developed by Stiesdal and his team is now being tested in Denmark. Large-scale production is scheduled to begin in 2014. The one-megawatt unit next to the company’s engineering offices in Brande looks tiny compared to the new super turbine.

And six megawatts isn’t the end of the story. For some time, Stiesdal and his team have been striving to achieve the many small improvements that will enable construction of a ten-megawatt unit with 100-meter-long rotor blades. The higher the output, the more efficient the turbines, and the cheaper the price of electricity.

There are limits to this megawatt expansion, however. “Ten megawatts will likely be the maximum for offshore turbines,” says Stiesdal, “and don’t expect to see turbines with an output of much more than four megawatts in wind farms on land.” Still, the optimized super wind turbines are sure to give coal-fired power plants a run for their money when it comes to cost-effectiveness, efficiency, maintenance-free operation, and longevity — and not just in New Zealand.