DANISH WIND TURBINE TECHNOLOGY LEADS THE WORLD

More than 20% of the electricity Denmark consumes is produced by wind turbines. And almost half of all the wind turbines in operation around the world are made in Denmark. Although in recent years industrial giants in many countries have started large-scale production of wind turbines,

Denmark’s Vestas Wind Systems still supplies almost a third of all wind turbines being erected on land and offshore. Danish wind turbines and wind turbine technology today generate electricity for more than 50 million people worldwide, a figure which will increase enormously in the coming years.

Danish sub-suppliers for the wind turbine industry also have a dominant position worldwide, e.g. in the production of blades, operating systems, gearboxes and brake systems. And Danish institutions and universities are among the world leaders in wind energy research. The Danish windturbine industry employs approximately 21,000 people and generates annual revenues of more than EUR 5.5 bn. Denmark’s leadership in wind energy is due to its history and culture, as well as far-sighted political flair. In the early years, when energy from relatively small wind turbines was much more expensive than energy from fossil fuels, wind energy was heavily subsidised. It gave a boost to manufacturers, who developed larger and larger turbines. At the same time, research into wind energy intensified in ever closer collaboration between manufacturers and universities. Today, wind energy is competitive with fossil fuels. And it is completely pollution-free when after 80 days of operation it has produced the energy it cost to produce the turbine itself.

http://www.ens.dk

http://www.windpower.org

THE WORLD’S LONGEST WIND TURBINE BLADE

WIND ENERGY: New technology and outstanding engineering have resulted in the construction of the world’s longest wind turbine blade at 61.5 meters, while at the same time reducing the weight

Does size really make a difference? In the wind turbine industry, the answer is a thundering “yes”. Size is everything. The taller the turbine tower and the longer the blades, the more energy is supplied to the wind turbine. But size also influences weight. The longer the blade, the higher the weight. And then a new difficulty arises, because the pressure on the blades creates stresses that require increased dimensioning of the other components of the wind turbine.

This problem has been solved by the world’s largest manufacturer of wind turbine blades, Denmark’s LM Glasfiber. The company produces the world’s longest blade at 61.5 meters, but with a weight of only 17.7 tons – less than the weight of some considerably shorter blades.

“The challenge of producing a large blade is not proportional to the length of the blade,” says head of information at LM Glasfiber, Steen Broust Nielsen. “Doubling the length of a blade does not mean doubling the development difficulty. The challenge is to optimise performance, weight and price. As a general rule of thumb, the weight of a blade increases by at least the cube of the length. But the LM 61.5 has proved an exception to that rule.” The team which developed the large blade put great efforts into choice of materials and production processes, and created a unique combination of fibres and resin components from which the blade is moulded.

“By keeping the weight under 18 tons, we have succeeded in reducing the stress on the wind turbine, thereby achieving significant savings on the dimensioning of its other components,” says Steen Broust Nielsen. “We have simply moved the limits for what is possible to do in blade production.” Since 2004, LM Glasfiber’s new blades have been rotating uninterruptedly on a 5 MW prototype wind turbine, which supplies power to 5,000 households in Brunsbüttel, northern Germany.

LM Glasfiber is the world’s largest manufacturer of wind turbine blades. The company has supplied 95,000 blades in total, corresponding to an electricity production of 25,000 MW – equivalent to the electricity consumption of 25 million households. LM Glasfiber has 13 production and service facilities in 8 countries. It supplies wind turbine blades to 9 of the 10 largest wind turbine manufacturers in the world. The company employs approx. 5,000 people and generates revenues of DKK 3,539 million annually (approximately EUR 500 million).

 

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RESEARCH INTO FLEXIBLE WIND TURBINE BLADES

WIND ENERGY: Risø National Laboratory, the Technical University of Denmark, conducts research into wind energy and is currently developing a wind turbine blade with a flexible trailing edge that can adapt to the wind. The aim is to imitate the wing action of a hovering bird.

A sizeable part of Danish research in wind energy is being conducted at Risø National Laboratory, the Technical University of Denmark (Risø, DTU). A research group is currently testing a wind turbine blade whose trailing edge can adapt to wind conditions. By equipping the blade with flaps, the blade can better exploit the energy potential of wind.

The flexible blade requires less strength, because it can yield to wind pressure. This makes the blade cheaper to produce, while at the same time the blade exploits the wind more efficiently because its shape constantly adapts to reduce the force of the wind as much as possible. The blade’s service life is thereby increased since the mechanical load on the blade is reduced.

Flexible trailing edge

“A flexible trailing edge reduces the large and damaging fluctuations down through the wind turbine,” says senior research scientist Christian Bak of Risø, DTU. “By protecting the turbine in this way, the risk is reduced of damaging gearboxes and bearings that are exposed to strong wind pressure.”

The idea can be compared to the flaps on aircraft wings that give the aircraft greater load bearing capacity at lower speeds during takeoff and landing. However, these variable-position flaps create noise and destroy the relationship between upward force and resistance, and thus cannot be used for wind turbine blades. Furthermore, flaps on aircraft wings are not continuously adjustable. So the research group is aiming to develop a turbine blade whose entire trailing edge is made flexible and can adjust very rapidly i.e. many times per second.

Optimising energy output

“The flaps we have tested so far are made of a ceramic material, which can be made movable by supplying power to it,” says Christian Bak. “A sensor and a control algorithm tell the actuators how to react to the approaching wind. It all happens at lightning speed, and will not only help to limit the load on the turbine, but also to optimise its energy output.” The research group has patented a blade trailing edge made of rubber. Inside the rubber trailing edge, cells have been constructed which can be inflated with air or liquid, thereby changing the shape. Blades with ceramic flaps and blades with a rubber trailing edge will both be thoroughly tested in a wind tunnel during 2008.

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HYDROGEN VALLEY

HYDROGEN SOCIETY: Hydrogen will have increasing importance in the future, both as an energy carrier and for industrial processing. A small Danish town aims to make itself the centre for this development

Mikael Kau has a vision of making Hobro the centre of Hydrogen Valley

Hobro is a relatively small town in northern Denmark, but it has large ambitions. Hobro aims to be Hydrogen Valley: the beacon that shows the way towards the hydrogen society of the future.

“I am convinced that the hydrogen society will be the future,” says Mikael Kau, director of the town’s growth centre, Cemtec, and the fiery soul of the visions regarding Hydrogen Valley.

“Hydrogen is the answer to the energy problems of the future,” he says. “There are undreamed-of amounts of it, it is pollution-free and the technological development is already so far advanced that it is financially competitive with fossil fuels.”

Commercial electrolysis plant

Hydrogen as an energy carrier is inextricably linked with fuel cells, but in addition, hydrogen is used in a large number of production processes which have nothing to do with fuel cells.

“Clearly fuel cell technology has great potential, but it requires far greater hydrogen production than today, and a completely new infrastructure for distribution and fill-up opportunities,” says Kau. “When Hydrogen Valley gets its own commercial electrolysis plant in the next 12 months for production of highly pure and cheap hydrogen, it is ensured success in business terms because of a neighbouring metal-sintering company that is a large consumer of process hydrogen in its production. In addition, Hydrogen Valley offers Denmark’s first industry plots dedicated to hydrogen-related companies, with an established and functioning hydrogen infrastructure.” Denmark’s world leading role in renewable energy is the dynamo for the ambition level in Hobro. “We must exploit the enormous research and knowledge mass we possess in largely all areas in renewable energy to also comprise hydrogen,” says Mikael Kau. “And Hobro’s location mid-way between three of Denmark’s leading centres for hydrogen and fuel cell research as well as bio energy research –the universities in Aalborg and Århus, and the Centre for Danish Agricultural Sciences near Viborg – makes the town an obvious centre for the cluster that is manifesting itself in the area.”

http://www.hydrogenvalley.dk

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