Power from the sky

Wind power is a clean and renewable energy source. German manufacturer Enercon offers a range of innovative windmill designs.

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Gearless is good
The German company Enercon is in the forefront of wind-generated power in Europe, thanks both to the company’s innovative windmill designs and the farsightedness and enthusiasm of Enercon founder, Aloys Wobben.
The gearless design of Enercon windmills means there are only two major bearings on either end of the main shaft, which carries both the rotor and the generator. SKF supplies the taper roller bearings that are installed on all the Enercon products. For Enercon’s most popular windmill, the E-40, for example, the bearings used are the 32048 X and the 32064 X, together with the necessary lock nut and sleeve.
SKF has been closely involved in the design of the bearing arrangements. Wobben says he admires the willingness of SKF staff to listen to questions and to come up with solutions.
He recalls that Enercon once dismantled one of its used windmills to check for wear and tear and sent all the components back to the manufacturers for tests. Many declined to participate in the exercise, he says, because the lab time necessary would be too expensive. SKF, however, performed the tests and came up with a report that resulted in improvements in the way the windmills were assembled. In addition, says Wobben, they improved their method of delivery to decrease the chance of damage to the bearings in transport.

Wind power is a clean and renewable energy source. German manufacturer Enercon offers a range of innovative windmill designs.

“I came here to study wind,” says Aloys Wobben, the founder of Enercon. He grew up not far away, in the Emsland region in northern Germany. But, as he says, the wind doesn’t blow quite as hard in that gently hilly country as it does here in Aurich in the East Friesland, a region even farther north in Germany. Now, there’s not much he doesn’t know about the wind that powers his generators, not just here in Aurich but all over the world, and it’s largely his knowledge that has helped Enercon become a technological leader in the wind energy field.
And technological leadership has been rewarded with market leadership. Enercon generated more wind-powered megawatts in Germany than any other manufacturer. This makes Enercon a major player in wind energy in Europe, since Germany is by far Europe’s biggest market. In 1996, Germany had a total installed capacity of 1,550 megawatts – nearly twice as much as Denmark, the next largest market. In the first six months of 1997, the amount of electricity produced from wind rose 230 percent over the equivalent period in 1996, although it’s still a tiny proportion, 0.3 percent, of the total electricity generation. The total wind energy production in 1997 was 2.7 billion kilowatt-hours.
Wobben came to wind-powered electricity generation via electricity. He studied electrical engineering at the Technical University in Braunschweig, Germany. He specialised in electrical control systems, despite his interest in wind. “I pulled out my pocket calculator and worked out the energy that was available in the wind,” Wobben recalls, “but you couldn’t make money with it.” Which is why, when he founded Enercon in 1984, the company made control systems. The first windmill wasn’t produced until 1985 (it’s still working in his back garden). But by 1988 production of windmills had taken over the company.

Technological breakthrough
Although Enercon’s earlier windmill models featured technical innovations, such as the use of variable rotor speeds to match wind conditions, the most significant breakthrough for the company occurred in 1992. It was then that the company introduced its gearless E-40 model, in which the rotor and the ring generator are on one axle, instead of being linked through a gearbox. This means there are only two major bearings on either end of the main axle, which carries both the rotor and the generator.
Enercon’s gearless system has several advantages: There is less mechanical energy loss; there are fewer moving parts; there’s less variability of operating temperature; and the system is quieter.
Another important innovation was the highly flexible grid-management system, which adapts the output to the needs of the grid. By electronically monitoring and adjusting voltage, frequency, output and the power factor, Enercon’s pulse-width modulated inverters can support weak grids and are well adapted for use with combined power-production plants such as solar-wind or diesel-wind configurations.
In addition to these innovations, the design of the rotor blades has been continually optimised. The rotor blades are handmade of glass-fibre-reinforced epoxy-resin. The aerodynamics, especially of the tip, have been improved to give optimum energy production from the maximum area swept by the rotor, as well as exceptionally quiet operation. A microprocessor-controlled wind monitoring system starts the blades when there’s enough wind, turns the rotor to face it, and adjusts the pitch of each blade individually to optimise the angle of attack.
The 500 kilowatt E-40 is currently the backbone of Enercon’s production in Germany, and some 1,100 are in operation around the world. But since 1992, other models have been introduced featuring the same basic concept. The E-30 (the numbers always refer to the rotor diameter in metres) is particularly flexible. It is available in versions for both high- and low-wind areas, producing 280 and 200 kilowatts respectively, and is suitable for regions where the grid conditions are insecure. It can be transported in standard containers and erected without a crane. The 1998 release E-58, is an 850 kilowatt version of the E-40. The E-12 is a lightweight, low-maintenance 30 kilowatt windmill for small users.

Stately improvement
The flagship of the Enercon fleet is the E-66, not just because it has the highest power rating of 1.5 megawatts, but because, with its elegance and sophistication, it represents a step forward in terms of aesthetic considerations. The E-66, designed by the famous British architect Sir Norman Foster, features a rotor that revolves at a much slower rate than other models. This makes it a more relaxing addition to the landscape. Near Enercon’s headquarters in Aurich, at the Holtriem wind park, which will eventually include 35 E-66 windmills, the huge rotors slide gently through the air, despite the strong wind. Just across the road, a flock of E-40s seem hectic in comparison.
The growth of Enercon, as well as other German wind-generator manufacturers, has been helped by legal provisions that have encouraged the development of wind energy. Since 1991, the law has required electricity companies to take electricity from renewable resources and to pay a certain price for it, until recently 17 pfennigs (US$0.09) per kilowatt-hour. The electricity companies oppose the law and have been conducting a campaign in the courts against it, on the grounds that it represents an illegal subsidy. They say the cost of electricity from imported coal (currently the cheapest source) is only around five pfennigs per kilowatt-hour, and they argue they should not have to pay more.
Wobben has little patience with such an argument. It’s a question of comparing like with like, he says. Imported coal cannot be compared with German-made windmills. In the first case, you import the pollution with the coal and you export the mining jobs. In the second case, you have no pollution and an industry that provides, according to some estimates, 10,000 jobs. In any case, says Wobben, if he imported his windmills from such low-wage countries as India (he already has a factory there) and if banks would allow an amortisation of the windmills over their expected life of 20 years instead of over 10 years as is currently the case, then wind-powered electricity could also be produced for around five pfennigs per kilowatt-hour. At the end of 1996, a new law was introduced that requires an electricity company to take electricity from “renewables” and to pay a guaranteed price for it only until renewables reach a certain percentage of the company’s total energy supply. In practice, this means that renewables will be restricted to about 10 percent of the market. Wobben is harshly critical of the new law. “Someone who makes such a proposal ought to be locked up,” he says. “They are instigating the pollution of the environment, and that is punishable with prison.”
And, he argues, traditional sources of energy are running out. Wind energy represents an obvious solution. The challenge is to ensure that wind power is seen as a standard part of the energy business. That means that, apart from reducing the price, wind power will have to be accepted as normal by banks and by the public.
Enercon is based on the energy and enthusiasm of Wobben, its founder, but he says he has put the company far enough ahead technologically that it would be able to regroup should anything happen to him. Meanwhile, Wobben continues to create new ideas, most of which he won’t make public until they’re ready to roll. He has already installed his first wind-powered desalination plant in the Canary Islands, and another will follow soon in Greece. And he’s also working on inverters for solar energy. So there is plenty in store for Enercon.

Michael Lawton
a business journalist based in Cologne

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