What is Offshore Wind Energy?

What is Offshore Wind Energy? Definition and Growth

Centuries ago, sailors used wind turbines at sea to propel their boats. Today, offshore wind turbines, a type of renewable energy, are used to generate clean energy for cities worldwide. What is offshore wind energy, and how has it helped produce cleaner, greener power?

When was the first offshore wind project?

By October 1990, news publications in Denmark were happily reporting a new development. The big, unsightly, and noisy wind turbines that elicited complaints from residents were going offshore.

The company building the offshore wind energy turbines, Elkraft, estimated the new electricity cost to be around 0.63 Danish kroner (5.8p) per kilowatt-hour, an increase of 70 percent from the cost of using inland wind turbines. Although each offshore wind turbine would not affect life on land with their noise, they were coming at a higher financial cost.  

Elkraft succeeded in 1991 by launching the first offshore wind project in Vindeby, Southern Denmark. It consisted of 11 wind turbines, each with a capacity to generate electricity of 450 kW. As of 2015, the farm was reported to have produced 450 GWh/billion-watt hours.

Since the first successful launch, many offshore wind turbines have cropped up worldwide. The biggest offshore wind farms are located in Northern Europe, specifically in the UK and Germany.

Vindeby Offshore Wind Farm
Vindeby wind farm in Denmark was the world's first. It consisted of 2 rows and 11 turbines. Something of an experiment, its owner, DONG energy, announced in 2017 pending decommission after 25 years of life. The lessons learned here will undoubtedly allow ongoing improvement as more and more energy producers look to renewable sources as we endeavor to do our best to wean ourselves off fossil fuels.

Cost of Offshore Wind Energy

Initially, these offshore wind farms were too expensive for many governments to consider feasibly sustainable. This was due to the high costs of constructing anything offshore, the price of mechanical parts for the wind turbines, and the constant maintenance needed to keep equipment working in a salty environment. Old reports revealed that the construction of each offshore wind energy farm required at least six vessels2.

However, just like any other emerging technology, these costs have come down significantly as it has advanced. With newer parties coming into the offshore wind industry (turbine manufacturing companies and offshore construction companies), the cost trajectory of offshore wind energy is lowering while output continues to increase.

How is Energy Created From the Wind Offshore?

Many of us are familiar with wind turbines, and they are one of the few sources available of clean energy. If you've ever wondered why we don't just power everything with wind turbines, the answer is quite simple. Not only do the gears (which turn to produce the electrical energy) need constant (and expensive) maintenance, the velocity of the wind on land is often not strong enough to produce enough output to match our energy needs.

With offshore turbines, there's the advantage of high wind. If you've noticed, it's almost always windy at the seaside. This is because of the relationship between air pressure and heat3. When the sun heats the land and sea, it never happens evenly. This means there is usually warm air and cold air present in the atmosphere. The warm air, which is lighter, rises. As this happens, cool air rushes under, and this is what we feel when the wind blows.

Offshore wind turbines are constructed in bodies of water to harvest offshore wind energy resources into energy using the more forceful wind available. They are usually constructed on the continental shelf or in the ocean, where the energy harvest would be higher. With the correct placement, these wind turbines can take advantage of high wind speeds and generate a higher amount of energy than could be feasible on land.

In Tune with Our Electricity Consumption

The operation of these offshore wind energy mills also lines up with consumer needs. In addition, offshore wind is usually stronger in the afternoon, making this its peak time for energy production. Consumers use the most electricity in the afternoon, and in this case, production and demand line up easily.

There's also the case of extremely long-distance transmission wires which line through most cities. With offshore wind turbines located close to cities, the need for these long-distance wires can be eliminated, along with more easily resourcing the demanding maintenance process that comes with them.

The Growth of Offshore Wind Energy

With Europe's proof that offshore energy is a worthy investment, realizing the advantages of renewable energy, many other regions around the world began their plans for offshore wind energy farms. As such, the success in Denmark and other European regions revealed that we could start making plans to reduce energy imports and cut down on fossil fuel which contributes to air pollution and greenhouse gasses.

In 2010, the US Energy Information Agency publicly announced its plans for offshore wind farm constructions. They stated that

Offshore wind power is the most expensive energy generating technology being considered for large scale deployment1".

Today, many more offshore wind farms are active in the United States, with 15 active proposals to install more waiting to be approved. However, the first offshore wind farm in the United States did not go online until 2016. It was developed by Deepwater Wind, an energy company, to replace the diesel generators used to power resorts in Rhode Island.

Europe still holds the position of the highest producer of energy through offshore wind farms, with a significant increase in offshore wind power capacity every year. Europe boasts of 105 offshore wind farms across 11 countries. When combined, their total output capacity is currently at 18.5GW.

Most of these numbers can be attributed to The UK and Germany, which produce about 85% of the total capacity. The world's biggest offshore wind farm, Walney 3 extension, is located in The UK. However, some European countries, such as Sweden and France, have shown little interest in offshore wind energy areas so far.

China's moves to offshore wind energy production

Like every other world development, China is catching up quickly with Europe on the deployment of offshore wind farms. In 2018, China was responsible for almost half of the global $25 billion investment into offshore energy.

Further, the Chinese government recently approved 24 new offshore wind parks, which they estimate will provide a yearly capacity of 6.7GW. After all, the country maintains its economic strength from manufacturing, and the Chinese government is hoping to reduce the impact of manufacturing on the environment.

These new projects aim to cut down on coal power and combat air pollution, which is a problem we've most likely seen in the news, denting their reputation.

Environmental Concerns with Offshore Wind

A man looks out while swimming at a sea of offshore wind turbines. Photo by Jack Hunter on Unsplash

As promising as offshore wind energy is, we cannot ignore some environmental concerns raised regarding its effects. Similar to onshore wind farms, environmental issues arise.

Marine experts have expressed concern that the noise generated underwater could interfere with marine life. Thus, sound-sensitive marine animals such as whales and dolphins are the most vulnerable to this possible harm. And the noise could affect their ability to communicate, feed, or even identify migration paths. Thankfully today, engineers working to solve this problem have solutions in play.

Developers are encouraged to install special foundation types to lower the noise produced by the wind turbine blades. Sadly, it might be impossible to silence these mills when they are at work altogether.

Other concerned parties exist. These include people subjected to the noise due to their proximity to the shore. Fishers also fear that their access to fishing waters may be cut off. Offshore developers will have to come up with solutions to manage these concerns.

We can say that the government is largely doing its part, in maintaining marine and human interest, specifically in Europe. Before applications are approved, the government must verify that the intended area is not an exclusion zone4, nature reserve, shipping lane, lighthouse cone, exploration area, or possible site for finding archaeological remains.

Offshore Wind Beyond the Developed World

In turn, as developed countries enjoy the benefits of offshore wind energy, the World Bank is considering installing offshore energy farms in developing countries with offshore potential.

Riccardo Puliti, the Senior Director and Head of Energy and Extractives at the World Bank, said:

“Offshore wind is a clean, reliable and secure source of energy with massive potential to transform the energy mix in countries that have great wind resources. We have seen it work in Europe – we can now make use of global experience to scale up offshore wind projects in emerging markets.”

With a budget of $5 million, the first countries being considered for this project are Brazil, Indonesia, India, the Philippines, South Africa, Sri Lanka, and Vietnam. As a result, this project could become an effective solution to tap offshore wind resources and solve the power problems these countries currently struggle with.

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1Levelized Cost and Levelized Avoided Cost of New Generation Resources in the Annual Energy Outlook 2019. U,S. Energy Information Administration. February 2019.
2Wind in our Sails: The Coming of Europe's wind energy industry, 2011.
3Arshad, Muhammad & O'Kelly, Brendan. (2013). Offshore wind-turbine structures: A review. Proceedings of the Institution of Civil Engineers – Energy. 166. 139-152. 10.1680/ener.12.00019.
4Giebel, Gregor & Hasager, C. (2016). An Overview of Offshore Wind Farm Design. 10.1007/978-3-319-39095-6_19.

Jen’s a passionate environmentalist and sustainability expert. With a science degree from Babcock University Jen loves applying her research skills to craft editorial that connects with our global changemaker and readership audiences centered around topics including zero waste, sustainability, climate change, and biodiversity.

Elsewhere Jen’s interests include the role that future technology and data have in helping us solve some of the planet’s biggest challenges.

Photo by Nicholas Doherty on Unsplash
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