Germany’s first offshore wind farm

After seven months of construction, Germany’s first offshore wind farm has gone into operation. “Alpha ventus” is the name of the 250 million euro facility located 45 kilometres off the North Sea island of Borkum. In the future, the wind farm will supply electricity for 50,000 households.

Far off the coast they stand in 30-metre deep water, the twelve test wind turbines of “alpha ventus”. It is by no means the first installation of its kind: more than 300 wind farms in the North Sea already supply electricity from the high seas. In the Baltic Sea, too, there are already individual wind turbines generating energy. Further plants are being planned or are already under construction.

One argument in favour of offshore wind farms is that they can generate almost twice as much electricity as wind farms on land. However, the construction of offshore plants is more complex and therefore more expensive. For example, most of the individual components have to be pre-assembled on land and then transported across the sea. The maintenance of the technology is also correspondingly more expensive.

Experts nevertheless affirm that the future of wind power lies at sea. The wind conditions here are simply better than on land. The German government plans that by 2030 more than half of the electricity generated by wind power will come from offshore plants. Wind turbines at sea are to make a significant contribution to implementing the German energy turnaround.

Sound insulation for whales

During the construction of wind turbines at sea, animals are exposed to great burdens from noise, criticises the Nature and Biodiversity Conservation Union of Germany. Seabirds, many species of fish and especially the protected harbour porpoises suffer from the noise generated when drilling and pouring foundations under water. Problem: The noise-sensitive harbour porpoises orient themselves and communicate via ultrasound. Sound waves under water could disorient them and cause permanent hearing loss. Researchers are now looking for effective sound protection so that the animals are not exposed to excessive stress.

Wind power

Many hundreds of years ago, people were already using the power of the wind. They built windmills that converted the energy of the wind into rotary motion. This enabled them to drive mill wheels to grind grain, for example. Because a lot of wind blows in the flat, seaside Netherlands, a particularly large number of windmills were built there: Some of them are still in operation today.

Wind still provides us with energy, in the form of electricity. Modern wind turbines work in much the same way as the old windmills: On top of a narrow tower sit huge rotors that look like propellers and are driven by the wind. The rotation of the rotors is transferred to a generator that converts the energy into electricity like a dynamo. The stronger the wind blows, the more electricity can be generated.

Where there is a lot of wind – for example on the coasts or on large areas – many wind turbines are combined to form large wind farms. Some even stand on platforms in the sea. In 2010, the first German offshore wind farm went into operation in the North Sea: Germany’s first wind turbine in the sea. The electricity generated in this way is transported by power lines to consumers.

Whether on land or at sea, wind farms have often been criticised: Their construction and rotation make noise and disturb humans and animals in the process. Some people don’t like the look of them either. But wind power has great advantages over other forms of energy: it is renewable. Wind will still be around long after oil, gas and coal have been used up. And it is “clean”, because it does not pollute the air and soil with pollutants from the burning of fossil fuels or with radioactive waste from nuclear power.

How is wind created?

A fresh wind often blows on the coast. If it blows particularly strongly, there is also talk of a stiff breeze. But it is not only at the seaside – everywhere on earth air is in motion. Only in a few places on earth is there not the slightest breeze, such as in the calme zone at the equator – named after the French word for calm: “calme”. This windless region used to be feared by seafarers because sailing ships could not get off the ground for weeks at a time. But why is it that sometimes there is a calm and sometimes a violent storm sweeps over the land?

Wind is created primarily by the power of the sun. When the sun’s rays heat up the ground, the air above it also heats up. The warm air expands and thus becomes thinner and lighter: the air mass rises. This creates low pressure near the ground. Where it is cold, on the other hand, the air sinks and high pressure forms on the ground. To compensate for the difference in pressure between neighbouring air masses, colder air flows to where warm air is rising. The greater the temperature difference between the air layers, the faster this happens. This is how the air gets into action – a more or less strong wind blows.

The formation of wind can be observed particularly well at the sea. During the day, the air over the land warms up faster than over the water. The warm air masses rise upwards and suck in the cool and heavy air above the sea: The wind blows from the sea to the land. At night, the wind changes direction. Because the water stores heat longer than the land, the air above is also warmer and rises. Then the wind blows from the land to the sea.

Which way the wind blows is always indicated by the compass direction. In our latitudes it is often from the west, we live in the so-called west wind zone. The hot trade winds, on the other hand, blow reliably from the east towards the equator. And the polar easterly winds transport icy air masses from the pole to the Arctic Circle.

Wind strength and wind speed

If smoke can rise vertically and there is hardly a breath of air, then there is no wind. In a hurricane, on the other hand, the wind is so violent that it carries even heavy objects with it. Wind can vary in strength – and the strength of the wind is indicated in the “Beaufort scale”, which ranges from wind force 0 with complete calm to a hurricane with wind force 12.

The scale is named after the British Sir Francis Beaufort, who used a similar scale a good 200 years ago. At that time, wind strength was determined, for example, by observing the height of the waves on a ship or the effect of the wind on the sails and then reading off the corresponding wind strength in a table. Today, each wind force has a specific wind speed. Wind force 0, for example, means that the wind is blowing less than one kilometre per hour.

This means that it is imperceptible – there is no wind. If, on the other hand, the wind is blowing at a speed of 39-49 kilometres per hour, i.e. almost as fast as a car in the city, then large branches are already moving. Such a strong wind has a wind force of 6. When the wind speed exceeds 62 kilometres per hour, it is called a storm. And a hurricane is on its way when the wind speed exceeds 118 kilometres per hour: This corresponds to the highest value on the scale, wind force 12. In this case, severe devastation is to be expected.

Incidentally, the strongest wind ever measured on the earth’s surface blew across Barrow Island in Western Australia in April 1996 at a whopping 408 kilometres per hour. Such a violent storm can blow railways off their tracks and cause buildings to collapse like houses of cards. The storm also brought terrible devastation to Barrow Island.