Wind energy and energy islands

To achieve a fossil fuel-free society that meets our increasing need for energy, it is necessary to expand the capacity of renewable energy technologies. In this connection, wind energy remains the cheapest energy technology we have available.

Picture of wind turbines lined up at Storebæltsbroen in Denmark. — More than 40 per cent. of the total Danish electricity production comes from wind turbines, and wind energy therefore constitutes an important element in the restructuring of the energy system, which will ensure that Denmark becomes independent of fossil fuels in 2050.

What is wind energy?

Wind energy is pollution-free energy produced exclusively by means of wind from wind turbines that can be set up both on land and at sea. Carbon is emitted during the production, transport and installation of wind turbines, but this emission is typically earned back within 6-12 months of a wind turbine’s service life. Wind turbines erected today have a design life of 25 years, but have often been shown to last for 30 years or more.

The global green transition is underway, and wind turbines are increasingly being used as a replacement for fossil-fuel power stations. According to the Danish Energy Agency, more than 40 per cent of Denmark’s total electricity production derives from wind turbines. Thus wind energy plays the key role in the transformation of Denmark’s energy system, and in the efforts to ensure that Denmark is carbon-neutral by 2050.

Today, wind turbines and wind energy account for less than five per cent of the total electricity produced in the world. However, the International Energy Agency estimates that this figure may be as high as 36 per cent by 2050. This will require that we continue to invest in wind turbines and wind technology in the future, so that we can become even better at utilizing wind power—not just in Denmark, but globally.

How does a wind turbine work?

The wind causes the wind turbine’s blades to revolve. This transfers energy to the blades. The energy is used to operate a generator installed inside the wind turbine housing (the nacelle). The generator creates current by means of electromagnetic induction, where a magnet is rotated in a chamber with coils. When the magnet rotates, the magnetic field in the coils changes, creating current. The current is usually passed on to the power grid, which forms the system of wires that transport the current out into the consumers’ sockets.

How is electricity from wind turbines utilized?

By far the majority of electricity produced from wind turbines is utilized in the public power grid, from which there are cable connections to most of our neighbouring countries. In 2021, wind energy accounted for 47 per cent of electricity production in Denmark.

The cable connections to other countries ensure that there is always a market for the energy produced. This is also the case when the weather is windy, and we have a surplus of wind energy in the Danish energy system. In addition, the cable connections are designed to ensure that we can import electricity from abroad when we have no wind and thus a deficit of electricity in our energy system.

Why do wind turbines sometimes stand still?

The reason why wind turbines sometimes stand still is that for long periods the majority of electricity production in the Danish electricity system largely comes only from wind turbines. During these periods, the wind turbines, in addition to other forms of green electricity production, also help to ensure a balance between the consumption and production of electricity.

For example, when a wind turbine stands still in windy weather, then it is probably due to the fact that at that moment there is a challenge to do with an imbalance between electricity consumption and production. When it stops, the wind turbine contributes to creating balance in the electricity system—which is necessary for security of supply in the regional electricity system we are part of.

This does not mean that there are too many wind turbines in Denmark, or that we don’t need more. In the vast majority of the other hours of the year, we need all the wind energy we can produce and more.

Because wind turbines account for a significant part of electricity production in Denmark, it is natural that wind turbines stand still once in a while. On the other hand, we can take comfort in the fact that our consumption of fossil fuels is falling as wind energy takes over.

In Denmark, there are more than 4,000 wind turbines on land and 500 at sea. With the energy agreement from 2018, a unanimous Danish Parliament declared that Denmark should continue to expand its wind energy infrastructure on land and at sea in the future.

Energy islands

Denmark has decided to develop and build two energy islands: one on Bornholm in the Baltic Sea and one to be established as an artificial island in the North Sea.

The islands will pool power from offshore wind turbines. The power must either be passed on to Danish consumers, sold to our European neighbours, or used to produce fossil-free, liquid fuels.

By 2040, the two islands will collect up to 12 gigawatts from offshore wind turbines. In comparison, Denmark currently produces about 2.3 gigawatts of offshore wind power, according to Green Power Denmark.

The energy islands will be the world’s first example of a fully decarbonized energy system, where power generation is based solely on renewable energy. This will be a completely new type of energy system that does not exist anywhere else in the world on such a large scale.

The construction cost of the North Sea island alone, DKK 210 billion—equal to five Great Belt bridges—gives a clear indication of the magnitude of the task. The project is so groundbreaking and comprehensive that research and development are needed to prepare for the best possible implementation of the energy islands.

If existing technologies such as offshore wind turbines and Power-to-X systems are simply copied and reused as they are today, there is a risk the project will be unnecessarily costly for Danish society.

Calculations from DTU and others show that with research, development, and innovative new solutions, we can save at least DKK 20 billion on the construction of the two energy islands.
This gives Denmark a unique chance to be among the frontrunners in the design of the energy systems of the future—solutions that we can export to the whole world.