Energy and resources from the ocean
WOR 7 The Ocean, Guarantor of Life – Sustainable Use, Effective Protection | 2021

The ocean as energy source – potential and expectations

The ocean as energy source – potential and expectations - fig. 5.20 Abstract ­Aerial Art/Getty Images

The ocean as energy source – potential and expectations

> The ocean is being promoted as a component of the energy transition. The principal advocates for this include large oil corporations. They are investing in the expansion of offshore wind energy and developing concepts for storing carbon dioxide beneath the sea floor. These technologies provide a ray of hope in efforts to shift away from coal, oil and natural gas. But for the ocean, this development means that many of its regions will be even more intensively and permanently exploited by humans in the future.

Deep and ultra-deep water
The term “deep water” originated during the time when offshore drilling platforms still stood on the sea floor. It ­referred to the maximum water depth at which this kind of bottom support was possible. But the number assigned to this depth increased with advancing technology. While a water depth of 300 metres was considered to be “deep water” in the 1990s, today the term indicates a depth of more than 500 metres. When resource experts speak of “ultra-deep water”, on the other hand, they are talking about water depths greater than 1500 metres.

A new era in the energy sector

Energy makes our lives much easier. In the form of electricity, it runs machines, trains and increasing numbers of automobiles. It allows real-time communication around the globe with pictures, and lights up apartments and ­entire cities after the sun has sunk below the horizon. In the form of heat, energy can melt ice and iron ore, and it keeps our homes cosy and warm when it is cold outside. ­Released by burning fuel in motors, it allows traffic to move and airplanes to fly.
Due to expansion of the world’s population, with growing numbers of people owning heaters, home electrical connections and automobiles, and with ever widening fields of their daily lives being electrified, there is also a rapid growth in global primary energy consumption. Experts define this term as the total amount of energy required to supply the global economy. Up to now this need has been mainly produced by burning fossil fuels. In Germany, for example, roughly 80 per cent of the energy used in the year 2018 came from coal, natural gas and petroleum products.
Looking at the production of electric current alone, two-thirds of the electricity used globally is still generated by burning fossil fuels. The greenhouse gas emissions of the energy and traffic sectors are correspondingly high. More than one-quarter of the oil and gas ­burned is pro­duced from the sea.
However, the energy sector is facing a radical transformation in two areas. The present power grids have to be expanded, modernized and intelligently managed in order to address the growing needs. At the same time, renewable energy sources such as wind, sun, biomass and hydropower are to replace conventional ones. Here, the ocean will also play a key role: for one, as a location for giant wind farms, and for another as a driver of wave energy converters and water-current power plants. There is also some discussion as to whether depleted natural-gas reservoirs beneath the seabed might be a ­suitable place to store carbon dioxide that has been ­captured from indus­trial operations and subsequently liquefied. At any rate, the storage potential would be ­enormous, and it is pre­sently of great interest to a number of oil- and gas-pro­ducing companies.

Oil and natural gas production in the sea

Many of the Earth’s oil and natural gas deposits are ­located beneath the sea. Formed over millions of years, the first of these to be drilled were in the Santa Barbara Channel off the coast of the US state of California at the end of the 19th century, although they were still within sight of the coast at that time. But shallow waters and close proximity to land ceased to be basic requirements more than 70 years ago. Due to improved exploration, drilling and production methods, oil and natural gas can now be retrieved from reservoirs in water depths greater than 3000 metres and more than 160 kilometres from the coast. However, the areas of deep-water and ultra-deep-water production are limited to the shelf seas on the continental margins. The deep-sea regions, which by far make up the largest part of the marine area, are underlain by oceanic crust, and have a very low or non-existent potential for the presence of oil or natural gas.
Drilling beneath the sea has now also achieved extreme depths. The deepest oil wells in the Gulf of Mexico, for example, extend for more than 6000 metres into the sea floor, and there are platforms whose drilling equipment could theoretically penetrate up to 11,400 metres below the bed under favourable conditions.
5.19 > A supply ship of the Norwegian ­energy company Equinor delivers technical equipment for oil production to the Johan-Castberg oil field in the Arctic. When the deposit in the Barents Sea goes into production it will be Norway’s northernmost oil field.
fig. 5.19 Even Kleppa und Øyvind Gravås/Woldcam AS/Equinor
Technological advances have also allowed oil companies to expand their operations into areas where extreme weather or environmental conditions previously pre­vented production. In 2016, for example, the two Nor­wegian energy companies Vår Energi AS and Equinor (formerly Statoil) erected the Goliat drilling and production platform in the Arctic Barents Sea, thus developing the world’s northernmost oil field to date. Development of another deposit, even further to the north, is already underway. Production in the Johan-Castberg oil field is projected to begin in 2023.
Oil and natural-gas production in the sea is very time-intensive, and also particularly cost-intensive. It can take up to ten years from the discovery of an offshore oil reservoir in ultra-deep water until the sale of the first barrel of oil. The costs for geological surveys and all of the neces­sary drilling and production technology typically total in the billions. The decision by a company to develop an offshore field or not is therefore not based on the current oil price, but with a view to projected price trends in the ­future. For this reason also, the levels of offshore production are not so closely tied to current price developments as are the amounts produced from deposits on land.
According to the International Energy Agency (IEA), the volumes of oil and gas produced from beneath the sea make up more than one-quarter of the total global production. There are now around 6500 offshore oil and gas production facilities in operation worldwide. The principal locations are the waters of the Near East, Brazil, the North Sea, the Gulf of Mexico, the Niger Delta and the Caspian Sea. While the amount of offshore oil production remained relatively stable at 26 to 27 million barrels a day from 2000 to 2018, gas production during the same time period increased by 50 per cent, to more than 1000 billion cubic metres. Another new development is that some opera­tional steps, such as the liquefaction of natural gas, are no longer carried out on land, but increasingly on special ships while still at sea.
fig. 5.20 Abstract ­Aerial Art/Getty Images

5.20 > These two oil-production platforms stand next to one another in Cromarty Firth, an arm of the North Sea on the Scottish coast. More than one-quarter of the world’s oil production now comes from deposits under the sea.
In this setting, the search for new oil and gas reservoirs in the oceans is a continuing process. Over the past two decades, the largest deposits have been dis­co­vered in water depths greater than 400 metres. Alto­gether, these make up around half of all the oil and gas deposits discovered during the period from 2008 to 2018 worldwide. Considering the new reservoirs individually, it is clear that only a few of them can produce oil. More than half of the newly discovered occurrences are classified as natural gas fields.
In spite of all the new discoveries, many plans for offshore development were put on temporary hold following the Deepwater Horizon disaster in the year 2010 and the collapse of oil prices in 2014. During the same period, between 2013 and 2016, the number of active production platforms fell from 320 to around 220. One reason for this decrease was the enormous expansion of hydraulic fracking on land, especially in the USA. Fracking involves the deep injection of liquids at very high pressure, which produces cracks in the dense shale and petroleum source rocks. The shale gas and oil trapped in the rocks can then be extracted, and the entire procedure is much less expensive than offshore drilling.
5.21 > Since the year 2000, the amounts of fossil-fuel resources produced from the sea have been increasing, a trend that can largely be attributed to the rise in natural gas production. This takes place primarily in shallow waters. Oil, on the other hand, is increasingly being produced in deep water.
fig. 5.21 after OECD/IEA, 2018

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The growing competition from fracking and the ­resulting price war forced adjustments in the offshore industry. Only highly promising drilling projects are now being carried out, and generally with much more efficient planning. The platform designs have been simplified, ­largely standardized, and in some cases even decreased in size. At the same time, the worldwide surplus of offshore equipment and services is contributing to a decline in ­operating costs. Whereas oil production facilities in Norwe­gian waters or in the Gulf of Mexico previously only made a profit when the market price for oil was ­above a threshold of USD 60 to 80 per barrel (159 litre capacity), modern facilities can now operate profitably at a price of USD 25 to 40 per barrel.
At present, companies are striving to further reduce costs by digitalizing certain processes of offshore production. They know that the reservoir for the next project will likely lie in even deeper waters or be further from the coast. It will therefore present the operator with more new challenges, be they technological, logistical or financial – whereby unexpected discoveries cannot be ruled out in coastal waters that have been sparsely explored so far. In 2018, experts from the USA compiled the following list of significant scientific and technological hurdles for the industry:

Looking through thick salt layers

In some regions, like the Gulf of Mexico and off the coast of Brazil, for example, oil deposits are present in the rock strata beneath thick layers of salt. However, these salt deposits, which can be up to two kilometres thick, are practically impossible to penetrate using conventional seismic methods. New analysis techniques and high-performance computers are needed that can analyse large numbers of geological datasets. Another problem is that salt dissolves when it comes into contact with drilling ­fluids. In some situations, it can even damage the drilling equipment or the borehole. Drilling through salt layers will therefore require new technology that is especially designed for salt.

Heat- and pressure-tolerant drilling technology

Conventional drilling equipment can be used at temperatures of up to around 175 degrees Celsius. In drilling for especially deep-lying deposits in the future, however, the ambient temperatures could be as high as 260 degrees Celsius. It would be hot enough in the borehole to bake a pizza. These temperature conditions would be destructive to many of the sensors and electrical components that are typically installed in the drilling system. For these kinds of operations, a drilling technology that is especially heat-tolerant, and that can withstand pressures 2000 times ­greater than the atmospheric pressure at the Earth’s surface will be required.

New installation and observation systems

Companies are increasingly foregoing the use of floating platforms for producing oil and natural gas in deeper waters. This can be achieved instead by the installation of a subsea wellhead on the sea floor. Oil or gas flows from this through a pipeline directly to the shore. However, subsea systems still need to be monitored. This requires remotely controlled monitoring technology such as autonomous underwater vehicles with sensors and cameras that can examine the production systems for leaks or weak spots.

Storm-proof production facilities

Hurricanes are a growing safety issue because they are becoming stronger, particularly in the Gulf of Mexico. Oil and gas production facilities in storm-prone regions around the world have to be able to reliably withstand these weather extremes. The use of advanced technology or the installation of remotely operated underwater systems is therefore essential.
Another challenge is posed by production equipment that has been in use for decades. According to the IEA, around 2500 to 3000 oil or natural gas production systems will become obsolete by the year 2040. Many of ­these are steel platforms in shallow water. However, much more complex facilities in the deep sea are currently being added to these. The most environmentally friendly way to dispose of these would be to completely dismantle the systems and scrap them on land. But it is now con­ceivable that other solutions may be found such as using them as locations or foundations for offshore wind ­turbines in some situations.

The sea floor as a repository for carbon dioxide

The idea of using oil or gas platforms at the end of their service as sites for producing electricity from wind power, however, is just the beginning. With the advance of global warming and increasing pressure for action, governments and industry are intensively discussing whether it would be possible to store carbon dioxide in depleted oil or ­natural gas reservoirs beneath the sea to help prevent ­further warming of the Earth.
The idea of carbon capture and storage (CCS) is by no means a new notion. A number of concepts and approaches have been under consideration for several decades. But it has simply been much cheaper for industry to release greenhouse gases directly into the atmosphere than to capture them at great expense and store them underground.
One of two exceptions is provided by the oil industry itself. Particularly in the USA, oil companies sometimes inject carbon dioxide into partially depleted oil reservoirs in order to increase the pressure on the remaining oil and force it towards the production site.
As an added effect, the carbon dioxide improves the flow properties of the oil so that it can be produced faster. In this kind of oil production, known as Enhanced Oil Recovery (EOR), a portion of the injected carbon dioxide remains below the surface and is thus permanently stored. At present, however, only 30 per cent of the injected carbon dioxide comes from industrial capture projects. The rest, like the oil itself, comes from the subsurface.
Norway has gone a step further. As early as 1996, the country had already transformed one of its former marine natural gas fields into a carbon dioxide repository. As part of the Sleipner project in the North Sea, carbon dioxide that rises directly at the site of natural gas production is captured, liquified and then sequestered at a depth of 880 to 1100 metres below the sea floor. The responsible Norwegian oil company, Equinor (formerly Statoil), has also been operating under the same concept in the Snøhvit field in the southern Barents Sea since 2007. With these two CCS projects, the company now injects around 1.7 million tonnes of carbon dioxide into the sea floor each year. This amount is approximately equal to the emissions produced by a small coal power plant. But that is only the beginning
According to its own reports, the company is now participating in more than 40 CCS projects and is de­veloping concepts by which carbon dioxide can be separated during industrial production on land, liquified, and ultimately transported by ship or through pipelines to injection stations at sea. One of these is Northern Lights, a large Norwegian project that plans to capture carbon dioxide produced in cement production and waste incineration in the greater Oslo area and transport it by ship to the CCS terminal in Øygarden on the west coast of Norway. From there, it will be pumped through a 110-kilo­metre-long pipeline to an offshore temporary storage ­station south of the Troll natural gas field in the North Sea, where the liquified carbon dioxide will ultimately be injected to a depth of 2500 metres below the seabed. All of the necessary technological systems should be in ­operation by 2024.
A group of companies in the Netherlands has similar plans. A depleted gas reservoir off Rotterdam (Porthos project) will serve as a carbon dioxide repository to store a portion of the 28 million tonnes of carbon dioxide released annually by the city’s port and adjacent industrial area. The project plan estimates that two to five million tonnes of carbon dioxide can be injected into the Porthos reservoir annually. It remains to be seen, however, whether the emission-producing companies will actually follow through on their statements of intent and participate in the expensive process of carbon dioxide storage.
The cost of capturing one tonne of carbon dioxide at a cement plant, transporting it out to sea and injecting it into the sea floor is roughly estimated to be more than 50 Euros. CCS projects will not be economically viable until the cost for carbon dioxide emission exceeds the costs of capture and storage. For this to occur, however, the taxes on emissions will have to increase as drastically as the ­prices for the emission certificates. According to the World Bank, in 2019 companies paid between one and 19 US dollars for every tonne of carbon dioxide released, whereby more than half of the emissions were taxed at less than ten US dollars.
5.24 > In the Sleipner gas field in the North Sea, carbon dioxide that rises to the sea surface during the production of natural gas is captured directly on site, liquified, and then injected at a depth of 880 to 1100 metres back into the seabed.
fig. 5.24 Kjetil Alsvik/Equinor
To date, initiators of CCS projects in Europe have been primarily focussing on the North Sea. This is partially due to the number of large industrial companies located in the coastal region, but also because of the ideal geological conditions beneath the floor of the North Sea. In order to store liquified carbon dioxide in the subsurface, a thick sand­stone formation with abundant large pores between the individual sand grains is required, so that the carbon ­dioxide can easily disperse through the pore spaces. Overlying this sandstone formation, however, there must also be a layer of fine-grained clayey rock to seal it off and prevent the carbon dioxide from rising into the shallower layers of the sea floor.
After injection, the liquified carbon dioxide spreads through the porous region and slowly begins to dissolve in the pore waters of the sandstone formation. This process alone takes several hundred years. The dissolved carbon dioxide may eventually react with the surrounding rocks. It can dissolve them and form new rocks (limestone and other carbonates) in which the carbon dioxide is then permanently fixed. Experts refer to this process as chemical neutralization of the greenhouse gas. It takes many millennia for this process to occur.
Reservoir rocks suitable for CCS are commonly ­located on the shelves and in marginal seas like the North Sea. The storage capacity of these alone is so large that they could contain an estimated 150 billion tonnes of carbon dioxide, which is roughly three times the annual total emissions from pre-corona times (2019: 42.3 billion tonnes of CO₂). Worldwide, there are at least 794 geological basins on land and in the sea where it would be theoretically possible to store carbon dioxide underground. Their combined storage capacity has been estimated at about 8000 to 55,000 billion tonnes of carbon dioxide. Of this capacity, 2000 to 13,000 billion tonnes are located in marine regions, whereby this calculation only takes into account the coastal waters (up to 300 kilometres offshore, maximum water depth 300 metres), and the polar seas are also not included.
5.25 > The greatest amounts of carbon dioxide could be stored onshore because the geological conditions are best there. Nevertheless, storage beneath the sea floor is being considered in many places, in part because the possible adverse consequences would be less severe than in inhabited regions on land.
fig. 5.25 after IEA, 2020
Nevertheless, even large-scale CCS projects would not be enough alone to curb anthropogenic carbon dioxide emissions sufficiently to achieve the Paris climate goal of limiting global warming to significantly less than two degrees Celsius. For this, a much broader spectrum of measures for reducing carbon dioxide concentrations in the atmosphere will be required. However, experts at the International Energy Agency say that CCS will still play a key role as an interim solution. This process should principally be implemented in the industrial sectors where carbon dioxide emissions are currently considered to be unavoidable, such as in the manufacture of cement, steel production, production of chemicals, generation of electricity in biomass or coal-driven power plants, and in oil and natural-gas production and refinement.
According to calculations by the International Energy Agency, existing power plants and industrial facilities could be equipped with capture technology at a scale that allows around 600 billion tonnes of carbon dioxide to be captured globally within the next 50 years. That is equal to 17 times the current amount of total emissions from the industrial sector. The total quantity of captured carbon dioxide would not have to be stored underground. Some of it could also be used for the production of synthetic fuels. Raw-material experts also argue that inexpensive hydrogen could be produced from natural gas with the help of CCS. This could then be employed as a low-emission fuel or energy source for new applications in transportation, heavy industry or in buildings.
Finally, projects for underground storage of carbon dioxide could also be considered where the carbon dioxide is extracted directly from the atmosphere and subsequently liquified, a process known as direct air capture. This procedure is currently very energy-intensive and thus still too expensive. But for the long term, experts believe that unavoidable emissions will have to be offset by some degree of direct capture of carbon dioxide from the atmosphere. Otherwise, the goal of zero emissions will be no more than wishful thinking.
When comparing the advantages and disadvantages of storing carbon dioxide on land with storage options in the sea, the sub-seabed seems to be the lower-risk option because, as yet, there are virtually no infrastructures there that could be exposed to potentially serious damage. For example, if the sea floor is subjected to minor vibrations caused by the dispersion of carbon dioxide in the subsurface, the event would presumably cause very little disturbance to the biological communities on the sea floor. But on land these could cause damage to houses or roads. In addition, CCS projects on land could potentially affect the aquifers in the vicinity. These could be at risk of salinization, or acidification in some circumstances, and this could also be accompanied by the dissolution of toxic heavy metals from surrounding rocks. In the sea, such effects on possible groundwater reservoirs would be insignificant as long as these are not being used or planned as sources for drinking water.
The situation would be similar if carbon dioxide were to escape unintentionally from the subsurface. On land the greenhouse gas would be released directly into the atmosphere; but in the sea the escaping carbon ­dioxide would dissolve rapidly in the water, adding to its ­acidification. A large leakage experiment by European marine researchers in the Scottish North Sea suggested that this acidification is very localized, and only affects an area of ten to 20 metres around the site of seeping. If the site is in an area with noticeable currents or tides, the acidified water is diluted and its immediate detrimental effects on the marine animal and plant world are limited.
The leakage experiment has also helped to determine what kinds of technology will need to be employed to ­reliably and inexpensively monitor storage reservoirs of carbon dioxide in the sub-seabed over extended time ­periods. The operators of the two Norwegian CCS facilities in the sea perform regular seismic investigations of the subsurface. From the sea-floor profiles generated, the scientists can determine which rock layers the liquid carbon dioxide has penetrated. According to the experts, an observation network of geophones and passively listening robotic systems would be a beneficial addition to this. The geophones could be distributed on the sea floor and record the sounds of pressure-compensating motions, cracks or quakes in the subsurface. The robots would have the same function but, unlike the geophones, they would be mobile. They could thus move along the sea floor above the reservoir and check for signs of weakness, vibrations or leaks

One terawatt is equal to 1000 gigawatts, or one million megawatts. All three units express the power output that, in the case of a wind turbine, for example, specifies the maximum amount of energy that the unit can feed into the grid at a given instant in time. Tera-, giga- and megawatt-hours, on the other hand, are expressions of how much energy the wind turbine produces in one hour. These, therefore, address the question of how much current has actually flowed within one hour, rather than the peak output.

It is a well-known fact that the sea floor of the North Sea is perforated by around 20,000 drill holes. Added to this, there are naturally occurring cracks, fissures and vents. The subsurface is therefore as porous as a sieve. Methane is already escaping from the sea floor through around 4000 of the drill holes. Injecting carbon dioxide into the sub-ground near these holes would only induce additional leakage. Therefore, for the North Sea at least, it will not be a simple task to find potential reservoirs for carbon dioxide that satisfy all of the requirements. These are:
  • located close enough to the coast to avoid high transport costs;
  • located in a marine region where carbon dioxide ­storage is legally allowed;
  • having reservoir rocks and an overlying caprock layer intact over a large geographic area;
  • not already being used or planned for other purposes, such as shipping lanes, conservation areas or sites of future wind parks.
In the case of the North Sea, this does not leave very much suitable marine area. This situation has prompted the German government to initiate a national research project to study the possibilities and legal framework for CCS projects in German territorial waters. The experts began work in August 2021. A summary of their findings is expected in 2024.
However, whether the large-scale storage of carbon dioxide in the seabed will ultimately become a reality for Germany, Europe and areas beyond is, and will remain, primarily an economic decision. If the levies for greenhouse gas emissions do not continue to increase, industries will have absolutely no incentive to invest in and press forward with expensive CCS projects.
5.26 > The offshore wind sector is growing, but at very different rates in various regions of the world. The greatest annual growth in capacity during the period from 2015 to 2020 was seen in countries like Great Britain, China, Germany and the Netherlands.
fig. 5.26 after IEA, Annual offshore wind capacity additions by country/region, 2015–2022, IEA, Paris,, 2021

Promising sector — offshore wind power

An analysis by the International Energy Agency sounds promising: If wind turbines were to be actually built in all of the near-coastal marine areas that are suitable for their construction, and connected to the electricity grid, these offshore wind parks could generate a total of around 36,000 terawatt-hours of electricity per year.
This would be enough to supply the entire economy and all the world’s house­holds with power from a renewable source at least until the year 2040, and maybe beyond if electricity consumption doesn’t continue to increase, which is not a realistic expectation. For comparison, in the year 2019, total global electricity consumption was 23,000 terawatt-hours. Roughly 0.3 per cent of this amount came from offshore wind turbines.
The urgency for producing electricity from renewable energy sources is growing every day. The reasons for this include more than just the steady advance of climate change. There is also the general increase in electrification of all aspects our lives and economies, including the transportation sector, heat supply and the growing need for cooling.
More than two-thirds of the electricity required for air conditioners, heating, robots, machines, e-mobility, computers and mobile telephones, however, presently comes from coal and gas power plants, although green electricity from renewable sources has become much ­cheaper. At the end of 2018, its share was 26 per cent of the electricity produced worldwide. If humankind is to meet the Paris climate target, it has less than 30 years to not only turn this ratio around, but to completely eliminate the generation of electricity and heat from fossil fuels by the year 2050.
Offshore wind turbines will play an important role in achieving this goal for four reasons. Firstly, they have the great advantage over onshore turbines that the wind at sea is generally stronger and more consistent. It can therefore generate more electricity for longer periods of time. Secondly, in many areas there is much less resis-tance from the population to offshore wind parks than to those on land.
Construction projects thus have a greater chance of being approved. Thirdly, of all known technologies for generating electricity from renewable sources, offshore wind energy has the greatest potential for expan­sion.
And, finally, offshore wind farms can be constructed near small islands (small land areas that depend on imported fossil fuels) or in remote coastal regions (poor supply lines for fossil fuels) and thus significantly contribute to the energy needs of previously undersupplied ­areas with sufficient inexpensive and clean electricity, one of the 17 Sustainable Development Goals (SDGs) of the United Nations.
5.27 > Worldwide, coastal states are investing massively in the expansion of offshore wind energy. If all of the projects presently planned are carried out, offshore wind parks with a total capacity of around 110 gigawatts will be connected to the electricity grids by 2025.
fig. 5.27 after Rystad Energy OffshoreWindCube
Because of the current state of affairs and the increasing societal pressure to act, the rate of expansion in offshore wind energy has risen significantly in recent years – driven primarily by investments from major oil-producing companies. During the period from 2010 to 2019, the offshore wind energy market grew by around 30 per cent per year, from three gigawatts of installed total capacity in 2010 to 29 gigawatts by the end of 2019. By that time, more than 5500 offshore wind turbines worldwide were connected to the electricity grid.
According to the International Energy Agency, ­another 150 offshore wind farm projects are expected to be completed by 2024, so that by the following year, one in five kilowatt-hours of wind energy will come from an offshore wind turbine.
The growing number of wind turbines in the German North Sea set a new record in 2020. According to the grid operator Tennet, with a combined capacity of 6679 megawatts, the turbines delivered a total of 22.76 terawatt-hours of electricity over the course of the year – an unprecedented yield. This is enough to supply around seven million households with green energy for one year.
The technology and expertise for the construction and operation of offshore wind turbines was developed primarily in Germany, Great Britain and Denmark. In 2019, Germany and the United Kingdom led the ranks of the largest offshore wind energy producers. However, China is presently making the largest investments in the construction of new offshore wind parks.

Larger wind turbines, lower electricity prices

The newest generation of offshore wind generators is equipped with larger turbines and many other improved technical functions that use the wind as efficiently as ­possible. For example, in 2023, when the first phase of the new Dogger Bank wind farm in the North Sea begins operation off the coast of Yorkshire, England, each of the 13-megawatt turbines will produce enough electricity with a single complete rotation of its rotor (blade length: 107 metres) to supply an English household with energy for two days.
In addition, new wind farms like Dogger Bank will be built at greater distances from the coast (100 kilo-metres and more), because the wind conditions are better further offshore. Because foundations on the sea floor are more expensive and technically difficult in deeper water, wind farm operators are now advancing the development of floating platforms like those used in offshore oil production. There are already 13 test sites globally, including in France, Portugal, Japan, South Korea and Scotland. Their initial performance results are promising. According to the Scottish operators, their five floating wind turbines produce more electricity than comparable facilities with fixed foundations. Experts therefore believe that floating wind farms could soon go into serial production.

Capacity factor
The capacity factor of a wind turbine is defined as the proportion of its maximum power output that it has generated within one year. The maximum value is the amount of energy that would have been generated if optimal wind conditions had prevailed throughout the entire year.

Due to numerous technological improvements, modern offshore wind turbines can now achieve a capacity factor of 40 to 50 per cent, and thus generate electricity with the same efficiency as many coal- or gas-fuelled power plants, even though the wind does not blow constantly. Offshore wind turbines are also more efficient than those on land, and have twice the capacity factor of photovoltaic systems. An additional advantage is that, unlike photovoltaic cells, offshore wind parks also generate electricity at night and under almost all weather conditions. In Europe, the USA and China, offshore wind parks produce particularly large amounts of electricity during the winter months. In India, the largest quantities of electricity are generated during monsoon periods.
Calculations by the International Energy Agency suggest that the cost of constructing and operating offshore wind-energy facilities will drop by more than 40 per cent by the year 2030, so that green wind electricity from the sea will soon be cheaper to produce than electricity from coal and natural gas. It will also probably be able even­tually to compete strongly with onshore solar and wind generation. The IEA experts are therefore predicting huge growth for offshore wind power. By the year 2040 the amount of energy generated in this manner is to increase by a factor of fifteen. The European Union alone wants to install facilities with a total capacity of 300 gigawatts by 2050.
5.28 > Advances in technology make it possible. Modern offshore wind turbines are becoming larger and taller. Each new turbine, with its long rotor blades, catches more wind than its predecessors. The result is that electricity from wind energy can be generated in greater amounts and, above all, less expensively.
fig. 5.28 after IEA, 2019
fig. 5.29 Miguel Navarro/Getty Images

5.29 > The European Union is focussing strongly on green offshore wind energy. Member states aim to install facilities with a total capacity of 300 gigawatts by 2050.
Because of the falling prices for wind energy from the sea, it is also being increasingly considered as an energy source for the production of green, or low-emission, hydrogen. This will be crucial for a number of uses that require a shift to low-emission energy sources, including the de-carbonization of industry, transportation and heat supply. Just as one example, the output of a one-gigawatt offshore wind farm with present technology could produce enough hydrogen to heat around 250,000 homes. In January, 2021, the German government commissioned a large research project (H2Mare) to investigate the possibilities for producing green hydrogen and its by-products such as methane, ammonia and methanol directly at sea with the help of offshore wind turbines, and thus keep the costs of hydrogen production down.
However, this is no reason for euphoria. In order to achieve the climate and sustainability goals of the inter­national community, the expansion of offshore wind ­farms will have to proceed twice as fast as it has been so far. For this to happen, the following are necessary:
  • the explicit political will and a relevant offshore ­energy strategy,
  • a clear legal framework,
  • large investments, and
  • progress in competitiveness, research and technology development.
5.30 > The Paris climate goal can only be achieved if humankind transforms its energy sector to renewable forms of energy. For this to be successful, calculations indicate that the offshore wind sector needs to be expanded to a total capacity of around 1000 gigawatts by the year 2050.
fig. 5.30 after IRENA, 2020

Policymakers must lead the way

For a long time, the construction of offshore wind farms has been a national concern. But as the wind farms become larger and the sites shift further from shore, there is an increasing need for cooperation among multiple countries. This is necessary for the purpose of regional spatial planning, as well as for addressing the question of which grid the green electricity should be ­delivered to. An explicit commitment by every coastal state to advance the expansion of offshore wind energy and to cooperate with others in large-scale projects is ­therefore crucial.
Such an expression of intent is manifested by the formulation of national or joint offshore wind strategies by individual states or communities of states. These set the various expansion goals, characterize development trajectories and outline research, technology development and knowledge transfer approaches. This establishes a setting for companies and investors that is reliable over the long term. The European Commission, for instance, published its strategy to harness the potential of offshore renewable energy in November 2020.
5.31 > In the temperate and higher latitudes the winds blow stronger and more steadily, so wind capacity factors would be significantly greater than in the tropics.
fig. 5.31 after IEA, 2019
A fundamental component of the EU strategy is its commitment to a systematic and transnational planning of all activities on and in the sea (spatial planning), by which a significantly larger number of areas and sites are designated for the installation of bottom-fixed or floating wind farms that do not interfere with other kinds of usage such as fisheries, shipping and tourism. Furthermore, the European Commission recommends that the EU member states use best-practice examples to guide them in their plan­ning, especially successful pilot projects that allow mul­tiple use of the wind farms or the areas occupied by them, such as combining them with fish, shellfish or algae cultivation in aquaculture farms.
Moreover, it is important to include everyone affected by offshore wind power in a dialogue from the beginning. According to the European Commission, offshore energy technology can only be truly sustainable and thus viable for the future if it does not have a negative impact on the environment and does not endanger economic, social and territorial cohesion in the affected region.

Green hydrogen
Hydrogen is a colourless gas. Depending on its origin, however, it is named by ­various colours. Grey hydrogen is obtained from fossil fuel by the splitting of natural gas. Carbon dioxide is also produced in this process and released into the atmosphere. With blue hydrogen, the carbon dioxide produced is captured and stored, and thus does not enter the atmosphere. Green hydrogen is produced by the electrolysis of water using electricity from renewable sources. This process is carbon dioxide free.

A uniform legal framework

The rapid expansion of offshore wind energy requires planning and legal certainty for all participants, as well as clearly laid out and transparent approval procedures. Among other things, this implies:
  • uniform procedures for evaluating and minimizing possible environmental impacts (especially under­water noise, damage to bird and marine mammal habitats, electromagnetic fields around sea-floor cables);
  • uniform standards, regulations and approval procedures for the planning and construction of offshore wind farms;
  • uniform regulations for connecting the offshore wind farms to the mainland and efficient transmission of current into the grid;
  • uniform standards and regulations for the operation and maintenance of offshore wind power facilities, as well as for protection of the safety and health of all workers.


High investments

The construction of offshore wind turbines consumes a lot of money. In 2018, building a wind farm with a nominal capacity of one gigawatt would have required an investment of USD four billion. Since then, however, construction costs have been dropping and investments in offshore wind farms have been growing. In 2020 they rose drastically by 56 per cent compared to the previous year, ultimately reaching a total of USD 50 billion. The European Union estimates the cost of targeted power expansion to a total capacity of 300 gigawatts to be up to 800 billion Euros.
A large proportion of that money will be used to expand the electrical grid and trans-border connection lines because without them the green wind power cannot be distributed over a wide area. States bordering on the North Sea are also planning to combine several offshore wind farms in clusters or hybrid projects whose connection networks can supply multiple countries with electricity simultaneously.

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Competitiveness, research and technological advances

Lowering the costs of green electricity from offshore wind farms will require efficient and competitive supply lines for all the necessary components and services. Further­more, supply of all the metals required for construction of the wind turbines (especially the rare earth metals) needs to be guaranteed far into the future. There must also be progress in research and technology. The following ­questions, for example, still need to be addressed:
  • In a large wind farm, how do the individual turbines need to be arranged in order to make optimal use of the wind without interfering with one another?
  • How do large wind farms influence each other, and how do they affect the local weather?
  • How should electric grids be built and managed to be able to feed in large amounts of electricity from different wind farms under high wind conditions, to distribute and, if necessary, store it, so that the current is always available when and where it is needed by industries and households?
5.33 > Photovoltaic arrays so far have been primarily located in shallow bays where they are protected from wind and waves. This installation in the Chinese coastal city of Zhangzhou is one example.
fig. 5.33 ­ViewStock/Getty Images
The substantial expansion of wind energy also presents a great challenge to marine researchers in determining the short- and long-term environmental impacts of the intensive and large-scale use of wind offshore. It has long been known that the noise generated during construction work creates high levels of stress for marine organisms. But how, for example, is the wind-driven mixing of the surface waters and the consequent oxygen and nutrient exchange with deeper water layers affected when large numbers of wind turbines impede the flow of air on the sea surface to some extent? Would this result in ­decreased algal growth and ultimately lower biomass ­production? This kind of chain reaction is theoretically conceiv­able, but scientists will have to investigate it more thoroughly to determine whether it occurs in the real world.
What is certain, however, is that with the growth of the offshore wind energy branch new jobs are being ­created. In the EU today 62,000 people already work in this sector. According to calculations by the International Renewable Energy Agency (IRENA), by the year 2030 the wind energy branch, including both onshore and offshore, will employ up to 3.74 million people worldwide. By 2050 the number of workers could increase to more than six million. Offshore wind farms not only provide a vital contribution to transforming our energy supply to electricity from renewable sources, they also represent a key sector in the sustainable marine economy. Without offshore wind power, sustainable development in the world and comprehensive decarbonization of our economy would be inconceivable today. Textende