In our previous article on how wind farms work, we have discussed a typical wind farm or wind turbine.  Today we are focusing on the offshore wind farm, i.e. how it works, how efficient it is, how much it costs to build, the world’s largest offshore wind farms, and much more in this piece.   After reading the article, you will have a broad understanding of offshore wind farms so come forward to talk about it.

Introduction

Offshore wind power, also known as offshore wind energy, is the power captured from the intensity of the winds at seas, converted into electrical energy, and distributed to the inland power grid.  It  is a continuously renewing and unlimited power source that produces no detrimental greenhouse gas emissions when converted to electricity.  Of course, it will be critical in our future energy production as we try to combat climate change and limit greenhouse gas emissions.

How Energy Efficient Offshore Wind Farms are?

Offshore wind farms are efficient because of the following reasons:

• Offshore winds are usually stronger than on land, hence offshore wind farms are more efficient than land wind turbines with a double power generating capacity as land farms. 
• Offshore wind farms are situated distant from populated areas, as a result, people are unlikely to be disturbed by the sound produced by offshore wind turbines.

How Much Does an Offshore Wind Turbine Cost to Build?

A typical turbine can cost anywhere from $3 million to $4.5 million, however big offshore turbines can cost from $10 to $40 million of dollars.  Manufacturing and installing the most powerful 12 MW (megawatt) wind turbine might cost up to more than $400 million.  Construction, transportation and installation, and maintenance are the three costing areas for utility-scale wind farms.

Employees must be supplied with safety from seashore threats and lightning, as well as transportation to the job site results in increasing the cost.

How Much Does Offshore Wind Energy Cost Per KWH (kilowatt-hour)

As compared to on-land wind farms, offshore wind farms are much more expensive i.e. having approximately 50% double the cost that of land turbines, however having extra benefits they are becoming more popular day by day. Across the globe, offshore wind costs between $0.09 to as much as $0.20 per kWh depending on which part of the world you are in. In addition to the cost of the equipment, the installation costs can be quite considerable as the farms need to be as stable as possible in the sea.

What are the maintenance costs of Offshore Wind Farms?

Periodic maintenance of offshore wind turbines is usually required twice or three times each year with an average cost of $50 to $70,000 depending on the size of the turbine.  These inspections may become more necessary as the turbine is installed and requires more service to be operational.

By comparing the prices it is clear that the maintenance costs of offshore wind farms are more than that of on-land wind turbines which are about $45,000 per year. 

What are the Largest Offshore Wind Farms in The World?

Some of the world’s largest offshore wind farms are the following:

One Hornsea (UK)

Hornsea One is the world’s largest offshore wind farm, with a total output of 1.2 GW (gigawatt).  It’s also the first offshore wind farm with a capacity of more than 1 GW  all over the world, covers about 408 square kilometers off the coast of Yorkshire, and contains 175 Siemens turbines, each having a power of 7 MW.

Anholt Offshore Wind Farm (Denmark)

The world’s second largest offshore wind farm, the Anholt Offshore Wind Farm, was constructed in 2013 having more than  400 MW energy output, located in the Kattegat strait between Jutland and the island of Anholt, provides enough energy to power 400,000 homes for a year, or 4% of Denmark’s total electricity usage.

BARD Offshore I (Germany)

Construction on BARD Offshore I started in March 2010, is the 3rd largest offshore wind farm in the world.  The project is about 60 sq. km in size has a 400 MW energy production capacity and is located about 100 kilometers northwest of Borkum Island in the North Sea.

How do Offshore Wind Farms get constructed?

See the video and read the steps given below:

Subsea wires are used to link turbine lines, one side of which is attached to an offshore powerhouse, and transformers in the powerhouse raise the energy and deliver the electricity to the coast.  The power from the London Array is sent to a substation in Graveney, Kent, where it is supplied to the Grid System through lengthy undersea cables.

A remote-operated vehicle (ROV) buries the wires on the seafloor and the TIV (turbine installation vessel) provides electricity.

After laying the wire, the mono-pile foundations (steel tubes with a diameter of around 5 meters) are lifted and put vertically on the seafloor using the TIV’s 400-tonne crane. A 1000-tonne hydro hammer is used to smash the mono-piles into the seabed to depths of 25 to 30 meters while the platform, ladders, and cable tubes are then attached to the yellow transition pieces, which are then positioned above the mono-piles.

The TIV can transport cables and foundations for around six wind turbines at the same time.  It will return to Harwich after unloading and installing six cables and foundations to attach another six.  This process will continue until all 175 foundations have been installed.

The wind turbines are retrieved from Harwich in groups of six when all the foundations have been installed and the TIV crane is used to transport these to the wind farm site and mount them on the foundations.  

First of all, the tower is constructed, then the  generator nacelle is mounted, followed by the three turbine blades and start generating electricity. 

Why do some people dislike Offshore Wind Farms?

Wind farms constructed on seas do not have so much impact on the environment as land wind farms but they generate noise, which can be harmful to the aquatic environment and can damage the marine ecosystem. This noise has a variety of effects on marine animals, such as fish and mammals, including forced migration out of feeding or reproductive zones, temporary hearing loss and distraction, tissue damage, and even death.

Technology Advancements in Offshore Wind turbine

Have a look at some of the companies contributing to offshore wind farms:

Vattenfall

Vattenfall has been extending its involvement in offshore wind farms, is a  Swedish company, which is partly state-owned, and has a broad energy-producing portfolio, i.e. three offshore wind projects larger than 150MW are now active in its portfolio.

Company website: https://group.vattenfall.com/

Iberdrola

The Spanish company was formerly the world’s greatest wind energy producer, but it was delayed to the offshore market. It dipped its toe into the waters off the coast of the United Kingdom in 2014, when its ScottishPower Renewables business collaborated with Ørsted on the 389MW West of Duddon Sands plant in the Irish Sea.

Company website: https://www.iberdrola.com/home

Innogy

The German company was a pioneer in offshore wind, constructing the 60MW North Hoyle project off the coast of North Wales in the United Kingdom and commissioning it in 2004.

Company website: https://www.innogy.cz/en/about-innogy/

Conclusion

Operating offshore wind farm is expensive, but as scientists and developers understand more about the mechanics and management of wind turbines, costs are falling.  They have a large initial investment, but it pays off in the long run as external issues linked with fossil energy, such as pollution, habitat damage, CO2 emissions, and a decline in the healthcare system, are absent with wind power.  The cost of wind electricity has dropped dramatically in the last ten years, wind farms continue to struggle to make a profit. Though few people in the energy market criticize wind electricity generation for its high initial cost, others understand that the environment comes first as this is a requirement and an alternative to carbon fuels. 

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