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Overview of wind power technologies
License SS BY-SA 4.0 _ Last Updated: March 15, 2021
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Basic definitions

                 Offshore Middelgrunden wind farm, Copenhagen, Denmark. 20 turbines, 2 MW each, Bonus (Siemens AG), I.Ciorici

Wind energy is one of the most significant and successful areas of modern energy from renewable sources. Over the past 10 years, the share of wind energy in world electricity production has increased from about 1% to 4.4% (Fig. 1), while its total capacity now amounts to around 50% of all renewable energy capacities (Fig. 2).

Figure 1-2. On the left – the increase in the share of wind energy in the total amount of electricity generated in the world. On the right – the share of installed wind power in the total volume of renewable energy, %.

Sources: Based on Data from IRENA (2020), Renewable Energy Statistics 2020, The International Renewable Energy Agency, Abu Dhabi; BP Statistical Review of World Energy June 2020

The use of wind power for human needs began several millennia ago. For example, in Egypt, sailing boats were widely used for transporting goods, and by the beginning of the 15th century sailing flotillas were primarily the technical basis for the discovery and development of new lands and the development of world trade. The familiar appearance of a modern wind turbine with a horizontal axis externally resembles windmills that have now become exotic (Fig. 3-4), which for many centuries have been used to grind grain or pump out water. In the Netherlands, in the 16th century, wind energy was used to saw logs into standard-sized timber, which greatly contributed to local shipbuilding.

Figure 3-4. Left - Windmill Kinder Dijk (UNESCO site). To the right - Amsterdam, Netherlands.

With the invention of electric generators, windmills began to be used to generate electricity. The first wind farm was built in Denmark at the end of the 19th century [1]. Modern history of wind energy began in the 1980s after another oil crisis.
Wind turbines are a single structure for converting the kinetic energy of the wind flow into mechanical energy, and then into electrical energy. This multi-stage energy conversion cycle requires the coordinated operation of all elements of a wind turbine and, accordingly, optimal design solutions. Despite the fact that there is an objective barrier on this path, since the efficiency of converting wind energy into electrical energy theoretically cannot exceed 59.3% according to Betz's law, there is a fairly wide field for creative search for optimal designs, given that the efficiency of modern industrial wind turbines does not usually exceed 40-45%.
Currently, wind turbines have several defining features. First of all, turbines with a vertical axis – VAWT and horizontal axis – HAWT are distinguished depending on the location of the turbine rotor shaft in relation to the base on which it is installed. Opinions regarding the benefits of each of these types of turbines often polarize. For example, in [2] VAWTs great efficiency, ability to withstand strong winds, ease of maintenance of this type of turbine, etc. are noted. Nevertheless, in today's industry horizontal axis turbines dominate, while the industrial deployment of VAWT turbines is still episodic. An interesting analysis of these disputes can be found in [3].
Wind turbines can be two, three and multi-blade. The most widespread are three-bladed turbines, which have higher reliability [4].
In addition, wind turbines are divided into onshore and offshore. The latter can be fixed-foundation offshore wind turbines or floating wind turbines.
Like any energy object, wind turbines are characterized by dimensions (tower height, rotor diameter), power, capacity factor, and many other indicators. One of the largest offshore wind turbines developed by General Electric - Haliade-X has a tower height of 260m above sea level, a rotor diameter of 220m, and each blade is 107m long. This turbine is capable of generating 67 GWh of electricity annually and has a unique capacity factor of 63 percent [5].

Wind resources

The efficiency of any wind turbine depends primarily on the characteristics of the wind flow. Wind on the surface of the Earth is caused by its rotation, as well as various anomalies -– the uneven flow of solar radiation in different areas, the roughness of the earth's surface (mountains, forests, cities, etc.), the physical condition of the surface layers (water, solid soil). As a result, air flow is generated to provide a new thermodynamic equilibrium. Despite the fact that it is practically impossible to accurately describe the movement of air masses in the atmosphere (just recall the notorious weather forecasts that are often extremely unreliable), it is possible to predict wind flows at a specific point on the Earth with the help of long-term meteorological observations or using special theoretical models based on this data. The importance of this information is illustrated by a simple fact laid down in the formula for the power of wind flow (P):

P = 1/2dAV3
where V is the wind speed; d - density of the air; A - swept area of the turbine [6].

It is also necessary to add the actual coefficient of energy efficiency, which is determined by its design features. In other words, the power of the turbine depends on the wind speed by a factor of three, and to a lesser extent on other factors. Modern wind energy is trying to squeeze out the maximum possible from each wind turbine; therefore the design of wind turbines is constantly being improved (to increase energy efficiency), the height of the tower on which the wind turbines are located (with a height less than the restraining effect of surface roughness on wind speed) and the diameter of the turbine rotor increases (and this increases the swept area).
When searching for a site to install highly efficient wind farms, consideration should be given to areas with satisfactory histograms of the ranges of wind speed and its stability. The latter is not always achievable in practice since the main consumers of electricity are concentrated where it has developed historically, and good wind is found in completely different places, for example in offshore areas. The seasonal factor introduces additional difficulties into this process, when, following a change in solar activity, the distribution of wind speeds changes over the usual time ranges.

Figures 5 and 6 show the average ten-year data on the results of three-hour measurements at a height of 10 meters of the actual speed and direction of the wind for the same days of the week -– in one case in the winter, when wind speeds reach their maximums, in the other in the summer, conditionally a "silent" period. In addition, the first picture contains data for the offshore region – east of the UK coast in the North Sea, and the second picture – in the onshore zone, in the lowland plain region of Lower Austria south of Vienna.

Source: Advanced Energy Technologies based on NOAA/NCEI/Data Access/

As can be seen from the figures showing 56 averaged results, they are based on measurements taken per week in the first embodiment; in only one case was the average wind speed lower than 3 m/s (red column), when most turbines stopped under operating conditions. In the second option this occurred 39 times, i.e. 70% of the time during the week of observation; a conventional wind farm in this region would be idle due to the absence of a minimum threshold for wind speed. In addition, each stop and subsequent start of the turbine requires additional energy costs. The frequency of changes in wind direction is also important. Despite the fact that the number of changes in direction in the offshore zone was slightly larger, the angle of rotation of the wind direction in the second example often reached 180o or more, which indicates less stability of the wind flow in the second example. However, for an offshore conditional wind farm, another equally serious problem is revealed - short-term gusts of wind above 25 m/s, which are marked in red. They were registered quite often - 8 times, although for this indicator, not averaged indicators, as in the present case, should be more relevant, but actual ones. Such gusts of wind can lead to emergency situations. Of course, it is necessary to take into account that the above data were produced at a height of only 10 meters, which is significantly less than the height of modern wind generators, which is usually 60 meters or more, but in any case, this is a convincing visual demonstration of the huge difference in wind energy potential depending on the region.

Information on wind resources in various countries and regions is presented in many publications and databases. Thus, detailed maps of wind speed in the USA and some other countries for various altitudes from 30 meters are presented in documents of the National Renewable Energy Laboratory (NREL) [7-10]. Compilers emphasize that maps (NREL-produced map) refer to areas with low surface roughness, for areas with slopes of more than 20% apply additional resource estimates AWS Truepower-produced / NREL-validated. NREL also proposed a classification containing 7 classes of wind power densities at various heights. So for 10 m and a wind speed of 4.4 m/s, Wind Power Density will be 100 W/m², and at a wind speed of 9.4 m/s - 1000 W/m². For a 50-meter height with a wind speed of 5.6 m/s, the density will be 200 W/m², and at 11.9 m/s – 2000 W/m². These data describe the extreme classes in the above classification.
In [11], the countries of the world are ranked depending on the size of the territory where the wind speed was in the range between classes 3 and 7 for a height of 50 m. Brazil, Canada, USA, Russia, Peru, China, Argentina, Australia, Ecuador and Norway are at the top of the rating. The direct correlation between the size of the country and the place in this ranking is obvious, although Ecuador and Norway are exceptions. If we analyze the data presented in [11] in such a way as to identify countries where at least 1% of the territory will be characterized by the highest classes of wind activity (classes 6 and 7), we can see the following results: Brazil, Canada, USA, Peru, Ecuador and Norway will remain in the new list, and such large countries as Russia, China, Argentina and Australia will drop out of it. However, the new top list would include Great Britain, Ireland, Sweden, Nepal, Chile, Afghanistan and some other small countries. Clearly, not every part of the country’s territory where there are satisfactory indicators of wind speed can be suitable for the construction of wind farms – in one case, other infrastructure facilities may interfere, in the second – remoteness of consumers, in the third –complex terrain and soil conditions, etc. Therefore, only a small fraction of the territory with good wind resources can be attractive for the construction of wind farms.
A world map with an estimate of offshore wind potential for most countries of the world is presented in [12]. According to this source, four countries have the potential of more than 10 PWh (1 PWh = 1012KWh) – Canada, Norway, Russia and Australia. Wind potential in the range of 5-10 PWh is available in several more countries, including USA, Brazil, Argentina, China, UK and Japan.

One of the first quantitative estimates of the world's wind power potential at an altitude of 80 meters is presented in [13]. To achieve this, the authors took available wind speed data at an altitude of 10 meters (obtained from the National Climatic Data Center) and extrapolated it to 80m using the Least Square Extrapolation Technique. The results were verified using Tower data from the Kennedy Space Center (Florida).  In total, measurements from 7753 surface stations and 446 sounding stations were analyzed. As a result, the authors obtained maps of the main continents with the distribution of the studied points with wind speeds at an altitude of 80 meters in the range from less than 5.9 m / s (class 1) to more than 9.4 m/s (class 7). Among the main conclusions in this work it is necessary to single out the following: approximately 13% of the stations in the world belong to class 3 and higher, where the average annual wind speed exceeds 6.9 m/s at an altitude of 80 meters, which is acceptable for ensuring the efficient operation of wind turbines. Moreover, the global wind potential in this work is estimated at more than 70 TW, which is enough to satisfy all the world's energy needs.
Currently, the Global Wind Atlas [14,15], prepared by the World Bank and the Danish Technical University (DTU) and first presented to the public at Wind Europe Conference in Amsterdam in 2017, is the most advanced source of assessing wind potential in the world.
The methodology of this development is based on modern modelling technologies that summarize climate data and information about a specific area and its surface roughness in high resolution.  As a result, the interactive cartographic materials obtained allow us to estimate the density of the wind flow, Wind Power Density, Wind Roses and Wind Speed ​​at an altitude of 50, 100 and 200 meters on a scale of 1 km, as well as providing a lot of other useful information. The development is presented to the public under a free-to-use license. According to the authors, this development can help interested government and commercial structures in promoting wind energy technologies at a higher level.
EnerTechUp produced an interactive wind speed map based on meteorological observations from the National Oceanic and Atmospheric Administration U.S. Department of Commerce [16], Fig. 7, available at the Advanced Energy Technologies website. It contains averaged data on wind speed and direction, temperature and wind gusts over a ten-year period for more than 15,000 points of observation on the planet where meteorological observations were carried out, mainly in the three-hour interval. For each point of observation, the following were calculated: average wind speed at a height of 10 meters (average speed), conditional working range in percent, when the wind speed was in the range of 3-25 m/s (operational share), total 3-hour intervals, intervals coverage of a year, and the average number of measurements per interval.

Figure 7. Interactive map of wind resources

Source: Advanced Energy Technologies based on NOAA/NCEI/Data Access/

With an arbitrary choice of a point on the map, it is possible to get its coordinates and a general characteristic of the results as, for example, can be seen in Figure 8.

Figure 8. Characteristics of measurement results for station L9-FF-1

Elevation: +0030.0m
Latitiude: 53.62
Longitude: 4.97
Average speed: 9.2 m/s
Operational share: 95%
Total 3 hours intervals: 151812
Intervals coverage of year: 100.0%
Average number of measurements per interval: 51

By activating the label ‘Show Report’ in the drop-down window you can see the following charts:
Charts 8.1 - 8.3:

It presents the daily maximum and minimum values of wind speed during a conditional year; the average monthly number of gusts of wind during a conditional year as well as daily maximum and minimum air temperatures during a conditional year. All estimates were obtained by averaging the actual data from the results of predominantly three-hour measurements over 10 years between 2004 and 2014.

Another group of charts 8.4 – 8.9 is largely adapted to wind power technologies. Here you can see the quantitative estimates of various indicators by the number of confirmatory measurements:

All data in these charts have been calculated under the same conditions as for charts 8.1–8.3.

Chart 8.5 allows you to set the proportion of the wind speed ranges; chart 8.7 allows you to determine the proportion of changes in wind direction during successive measurement cycles, i.e. from one measurement to another; Figure 8.8 illustrates the monthly average number of changes in wind direction and the total extent of U-turns in degrees. For example, from this diagram it follows that in October a conditional wind turbine exactly following the direction of the wind should have turned around its axis more than 200 times in almost 2500 starts and stops. All these results can be useful in the design of wind farms, including determining the efficiency of wind turbines and the prediction of operating costs.

Mainstream technologies and wind turbine design

The design of any wind turbine must include all necessary equipment to convert kinetic wind energy first into mechanical and then into electrical energy. The main components of a modern three-bladed wind turbine with a horizontal axis are shown in Figure 9. Most industrial wind turbines are multi-ton constructions requiring a substantial foundation. Plate steel turbine towers reach from tens of meters up to 260 meters above sea level, as seen above in [5].

Figure 9. Design and main modes of operation of a wind turbine

1. Tower&main frame - 29,1%*

2. Yaw system - 1,25%*

3. Nacelle housing - 1,35%*

4. Rotor blades - 22,2%*

5. Rotor hub&bearings - 2,59%*

6. Gear box -12,91%*

7. Brake system - 1,32%*

8. Generator - 3,44%*

9. Anemometr

10. Cables - 0,96%*

11. Pitch system - 2,66%*

* - Cost-sharing of main components for
5 MW Wind Turbine
Source: EWEA

Two prevailing trends in the development of wind energy present additional requirements for the construction of wind turbines: one, an increase in the size of wind generators and two, an increase in the number of offshore wind farms. According to [17], beginning in 1990, the average height of wind generators increased from 40 to 128 meters, and the rotor diameter from 24 to 109 meters. This made it possible to increase the capacity of wind turbines by more than 50 times. Further, over the past ten years the total capacity of offshore wind farms has also increased significantly, and now exceeds 23 GW. Concurrently, the capacity factor significantly increased both globally and in key countries in the field of wind energy, determined as the ratio of the real volume of electricity generation to the maximum calculated if the turbine operated at peak capacity (Fig. 10-11). This increase was the result of the improved efficiency of wind turbines, achieved by methods including: increasing the height of the tower to capture a larger wind flow (and consequently increasing the duration of the operating range); by increasing the overall share of offshore wind turbines; increasing the reliability of the entire structure and thus reducing downtime; and by improving operational technologies. The greatest efficiency is seen in offshore wind farms, where more productive wind flows are concentrated. Currently, the majority of offshore wind turbines are of a fixed foundation design, however, production of floating wind turbines is expanding.

The most important structural elements of a wind turbine are blades. They operate in extremely harsh conditions, receiving the wind flow and ensuring the rotation of the rotor. Like towers, the blades of a wind turbine are many tens of meters long, sometimes exceeding a hundred meters [5]. With such dimensions, the blades require high strength and rigidity, but with a small overall mass; to achieve this, therefore, composite materials are used in their manufacturing. These are often fiberglass and epoxy-based composites. Recently, carbon fiber materials have been used more frequently, which, despite a higher cost, can significantly reduce the weight of the blade and hence the load on the other components of the wind turbine. It should be noted that today the maintenance, repair and replacement of wind turbine parts present the greatest barrier to achieving the optimal operating load, which so far remains low. In addition, these activities account for a substantial share of operating expenses. Therefore, ensuring the high reliability of operation of all structural elements - and particularly the blades - is of paramount importance in developing technologies for the production of components and their operation.


                                              Wind farm Ignacio Molina (Casares), Malaga, Spain. Enercon, power 2 000 kW, diameter 70 m, aenert

A nacelle is installed on the tower, in which the main actuators of the wind turbine are placed – the rotor and blades, a primary low-speed shaft, the gear box, generator, and a brake system. To position the wind turbine relative to the direction of the wind, a yaw system is used, which works in conjunction with a wind vane, anemometer and includes its own drive mechanism. This system allows for the efficient operation of the wind turbine and increases the reliability of mechanical components, protecting them from fatigue stress. Another important control system included in the wind turbine is the pitch system. This system controls the angle of attack of the wind flow by adjusting the angle of the blades. The angle of inclination of the edge of the blade - in relation to the direction of the wind - can significantly adjust the power output, up to a complete stop of the wind turbine. Electrical equipment includes a generator, a controller that starts or stops the turbine depending on wind speed, and elements (cables, contactors) for connection to the electric grid. In addition, many wind turbines include a lightning protection system, a fire extinguishing system, and a de-icing protection system.

Fig. 10-11. Change in the share of offshore wind capacity in global wind capacity over the past 10 years. Dynamics of change capacity factor by Wind power generation in 2009 - 2018.

Sources: Based on Data from IRENA (2020),  Renewable Energy Statistics 2020, The International Renewable Energy Agency, Abu Dhabi

Turbines with a fixed foundation are installed in shallow water at a depth of up to 30 meters, with designs including single column gravity base structures and tripod piled structures [18].

Most offshore wind farms are found within 60 km of the coastline, but there are examples in Great Britain and Germany located up to 90 km at sea [19]. Beyond a depth of more than 60-80 meters, fixed foundation turbines become very expensive and potentially technically unfeasible. Therefore, at these depths floating wind turbines are being used, Fig. 12.

Fig. 12. Floating offshore wind turbines

A - Total hight of wind turbine

B - Distance from a reservoir bottom to wind turbine submersed base

1 - Wind turbine blade

2 - Wind turbine nacelle 

3 - Wind turbine rotor cup

4 - Wind turbine tower

5- Electricity cable

The turbine has a surface structure, which differs little in appearance from onshore turbines, and an underwater structure or flotation element, which can extend several tens of meters deep and is tethered to the seabed by means of special ropes. Generated electricity is transmitted to coastal services via underwater cables. A turbine of this kind has been tested by Siemens off the coast of Norway since 2009: the Hywind Turbine with a capacity of 2.3 MW. The lightweight nacelle of this turbine, in combination with new controller algorithms for rotor pitch and yaw drive regulation allowed Siemens, after successfully completing the experiment, to proceed with the implementation of the first commercial project off the coast of Scotland called Hywind Scotland and put it into operation in late 2017. The project features five Siemens Wind Power SWT-6.0-154 turbines with a total capacity of 30 MW. The height of each turbine was 101 meters, and the diameter of the rotor was 154 m [20-21].

Fig. 13-14. Onshore (left) and offshore (right) windparks in the USA and in Denmark

A typical mode of operation of a wind turbine is shown in the graph of Figure 9. A turbine usually begins operating at a wind speed of 3 m/s (cut in wind speed), and at 25 m/s (cut out wind speed) the turbine shuts down. The turbine restarts when the wind speed drops to 23 m/s (re cut in wind speed). The current turbine output is dependent on wind speed. To monitor the efficient operation of the turbine and maintain rated power, monitoring and control systems are used, including the aforementioned pitch system and yaw system.

Advantages and disadvantages

Modern wind energy constitutes an outstanding technical, innovative and administrative achievement, a successful fusion of advanced technical solutions, state and public patronage, and bold investment. Of course, wind power is not a panacea; it has both significant advantages and disadvantages. Technical and organizational solutions used in wind energy are based on existing principles and technology. Currently, it can be reasonably argued that, while it has not yet peaked, wind energy has reached, the mature phase of its development. This allows it to compete with traditional energy resources both in terms of price characteristics, which is very important for consumers and operators, and in that it encourages investment.

By far the most important advantage of wind energy is its minimal negative environmental impact. The significance of this factor, supported by competitive prices for manufactured products, has determined the rapid developments in this sector. Today, despite the relatively small share of wind energy in the global balance of power generation – less than 5% – not a single energy strategy, not a single energy forecast can do without considering the role of wind energy. Nevertheless, nothing stands still, including the development of competitive technologies, so the timely identification and detailed analysis of the existing shortcomings of wind energy is the subject of serious research and the basis for decision-making.

The inherent weakness of wind energy, and one common to other renewables, is the variability of the used natural energy. Wind is inconsistent both in its dynamic characteristics (speed, gusts, periodicity), and in direction. Hence, wind energy has a relatively low capacity factor. The designs of modern wind turbines can largely overcome these difficulties; however, this does not solve the main problem – ensuring a reliable power supply to the network from wind farms. In other words, wind energy, and its consumers, are at the mercy of meteorological forces. The solution to this problem can take various forms. One option is the systematic integration of wind farms into the existing electricity grid where interruptions in the supply of electricity from wind energy can be compensated by other available sources. However, the key words here are “available sources”, which implies, firstly, their presence, secondly their redundancy, and thirdly their mobility, i.e. the possibility of instant power control. If, for environmental reasons, we exclude fossil-fuel power plants from the existing list of electricity producers, then there will be few other options. In essence, taking into account the scale of the task, the alternative to fossil-fuel stations could be hydropower plants and pumped storage plants or the creation of hybrid energy parks, where the wind farm will be paired with, for example, a solar or geothermal station. In regions rich in water resources, for example, in Austria or in the south of Germany, this presents a realistic solution, but it is not feasible in many other regions without such natural advantages. Other technical solutions to this problem are equipping the wind turbines with their own accumulating sources, for example, lithium-ion batteries, hydraulic accumulators or compressed air storage, as well as the organization of associated hydrogen production, which can be stored separately or mixed with natural gas (power-to- gas), for subsequent balancing of power in the power system. An overview of these technologies, as well as a list of existing projects can be found in the following publications and databases [22-27].

The presence of a water battery [25] would allow for the possibility of non-stop electricity production by wind turbines. A water battery consists of a pump storage system, which typically includes upper and lower tanks and equipment for pumping water between them. While in operation, wind turbines can make use of the generated electricity to pump water from the lower reservoir to the upper one, these reservoirs being generally located in the tower of the wind turbine itself. When the wind turbines stop due to insufficient wind power or for maintenance, water from the upper reservoir is transferred to the lower one, rotating the hydraulic turbine and generating electricity. Thus, continuous generation of electricity by the hybrid power system is maintained. The pilot project launched by developer Max Bögl Wind AG in Gaildorf near Stuttgart has the following characteristics:

Wind farm capacity - 4 turbines of 3.4 MW each;
The diameter of the rotor is 137 m;
Tower height - 178 m;
Pumped-storage plant capacity - 16 MW;
Water fall height - 200 m;
Hours of storage capacity - 6 hours.

Among the main advantages of the system, in addition to the main target purpose itself – energy storage – it is necessary to highlight:

- a standardized power plant concept;
- the system is suitable for fresh and salt water;
- its short construction time and simple approval process.

Fig. 15-16. Water Battery in Gaildorf

Photos: Google Maps

To a large extent, the problem of continuous electricity generation is solved by increasing the size of wind turbines. It was mentioned above that, according to [17], over the past 30 years the average height of the tower has increased more than three times, which provides more advantageous operating conditions for the wind turbine due to its placement in the zone of improved wind flows, the stability of which increases with height. This is also facilitated by the increase in the number of offshore wind farms located in regions of higher wind activity. Fig. 17, provided by EnerTechUp, shows a map of the wind speed in Europe, which shows the calculated indicators of wind speeds in the operating range of the wind turbine (3-25 m/s) based on data from [16]. Extremely favorable conditions are found in the marine areas of Northwestern Europe, where operating time can reach 90% of the total, even at an altitude of 10 meters. As a result, the UK, Germany, Denmark, as well as Belgium and the Netherlands are among the world leaders in the number of installed offshore wind farms [19, 28].

Fig. 17. Distribution of sites with operating ranges of wind speeds in Europe

Source: Advanced Energy Technologies based on NOAA/NCEI/Data Access/

The disadvantages of this trend are that they present harsh operating conditions for wind turbines. This necessitates greater demands on their reliability, and perhaps most importantly, significantly complicates their maintenance. The installation, repair and maintenance of wind farms in offshore regions requires a considerable number of specialists in niche professions – divers, installers, high-altitude pilots, rescuers, etc., as well as special vessels, unconventional equipment and the effective organization of these resources. Strong winds impede the operation of maintenance services, significantly limiting their potential in terms of technical capabilities and safety.

Capital Expenditure (CAPEX) for the construction of wind farms and levelized cost of energy (LCOE) of wind energy in comparison with other energy technologies can be considered both an advantage and a disadvantage depending on the factors considered. The structure, price ranges and historical trends in capital expenditure of wind energy are described in detail in [29-33]. In [29], overnight costs for onshore and offshore wind farms are shown to be slightly more than $1600 and $6500/kW, respectively (2018). In an earlier 2010 study [31], these costs were estimated at approximately $2000 and $3300/kW (with variations of + _25-35%), respectively. In both papers, the authors took the US market as an example. According to this data (Table 1), capital costs for the construction of wind power facilities are comparable with competitive renewable energy technologies, but are noticeably higher than advanced fossil fuel technologies:

Table 1. Overnight cost of electricity-generating technologies [29]

TechnologyTotal overnight cost
(2018, $/kW)
Conventional gas/oil combined cycle999
Advanced combined cycle794
Conventional combustion turbine1,126
Advanced nuclear6,034
MSW - landfill gas8,895
Conventional hydropower2,948
Wind offshore                                   6,542
Solar PV – tracking1,969
Solar PV – fixed1,783

The structure of the offshore wind farm CAPEX cost breakdown is considered in more detail in [33]. Balance of plant (detailed design of the infrastructure and supply of all parts of the wind power station, except for turbines) is the most costly aspect and is estimated at 37% of total capital costs; turbine costs amounted to 33%, of which the rotor’s share was 11% , and the nacelle’s was 22%; installation & commissioning (installation and commissioning up to the issuance of any certificate of acceptance) was 26%; development & consent (which includes the process from the start of construction to the time of financial closure or readiness for construction) – 4%.

Compared with the previous study, in [31] the cost of the most expensive component of a wind farm – the wind turbine – was estimated at almost 70% for an onshore station, and 50% for an offshore station. The historical trends of the installed cost of wind farms are described in detail in [32]. The global reduction in capital costs of onshore wind energy occurred between 1983-2000 (from $5,000/ kW to $2,000/kW), followed by a period of stabilization until 2012, after which there was still a moderate cost reduction. This later period saw costs decreasing from about $2,000/ kW to $1,500/ kW. A smoother decrease in this indicator is typical for countries such as India, China and Germany. The history of the cost of installing offshore wind farms has a completely different dynamic. After a relatively long increase in cost (2000-2013) from about $2,500 to $5,400/kW, a period of marked decrease began, reaching $4,300/kW in 2018. The average cost of turbines in this case amounted to $1170/kW for China to $2030/kW for the UK [32].

In Expenditure (OPEX), the maintenance aspect is usually the costliest. For example, for offshore wind farms, maintenance expenses can reach 38%, even larger than that for port expenses – 31% [33]. Levelized cost of energy (LCOE) as a specific characteristic equal to the Cost of Capital & Operating Expenditure related to the total energy capacity produced by the wind farm over the entire period of its operation determines the price of products between subsidized and profitable modes of electricity production. This indicator also allows the level of competitiveness between different energy technologies to be compared.

Summarized data on the cost of electricity generation from both renewable and traditional sources in Germany in 2018 is presented in [34]. It shows that wind energy is a very competitive source of energy production; the cost of electricity production by onshore wind farms in 2018 was between ​​3.99​​ € cent/kWh and 8.23 ​​€ cent/kWh with a unit cost between €1,500/kW and €2,000/kW. This is comparable to the cost of electricity production by photovoltaic plants, as well as coal plants using lignite (between 4.59 € cent/kWh and 7.98 € cent/kWh) or other coal (between 6.27 € cent/kWh and 9.86 € cent/kWh) as well as power plants with a combined cycle (€7.78 up to 9.96 € cent/kWh). For offshore wind farms, the numbers are less competitive – with unit capital costs between €3100 and €4700/kW, with the cost of electricity ranging from 7.49 to 13.79 € cent/ kWh.

Fig. 18-19. Wind energy has reached a high level of competitiveness. Left: Germany, where the wind farms are planned to replace nuclear power. On the right - Austria, the wind farm neighbours’ oil production site.

Predicted comparative LCOEs of various technologies in the USA in 2021, 2023 and 2040 as part of the National Energy Modeling System (NEMS) for the U.S. Energy Information Administration’s (EIA) Annual Energy Outlook 2019 (AEO2019) are presented in [35]. For example, in 2023, the predicted LCOE for onshore wind was $42.8/MWh, and for offshore wind $117.9/MWh, while for power plants with conventional combined-cycle (natural gas) this value was estimated at $42.8/MWh. Hydropower has the lowest LCOE values of $39.1/MWh.

A detailed analysis of the historical changes in LCOE for renewable energy technologies can be found in [32]. Since the beginning of the commercial operation of wind farms in the eighties, the LCOE  for onshore wind turbines has decreased from $0.3/kWh to about $0.5 - $0.6/kWh. This process has been relatively stable with only slight fluctuations. Between 1984 and 2018, LCOE in the U.S. decreased by 83%, in Denmark by 75%, and in Germany by 69%. In China, since 1996, this decrease has amounted to 73% [32]. LCOE for offshore wind farms reached its peak values ​​in 2014 and averaged approximately $0.18/MWh, having decreased by 2018 till $0.10 - $0.15/MWh [32].

Criticism of wind energy is often based on such factors as negative visual impact, noise pressure, rural industrialization, loss of habitat for wild animals, and the mortality of birds and bats, etc. Of course, further industrialization, especially as the fight against global warming continues, causes certain discomfort to people. However, following the aggressive use of terms such as “negative visual impact”, “rural industrialization”, etc. it should be recalled that ecological heritage of the previous period of industrialization was abandoned mines, smoky cities, and industrial diseases. At its unveiling the Eiffel Tower caused a storm of indignation among many, including progressive minds; however, today it is unlikely that anyone will condemn its aesthetic impact. The development of wind energy is of particular concern to numerous wildlife advocates. It should be noted that a huge number of studies, as well as existing programs, are devoted to this issue, some of which are mentioned below [36-44]. For example, in [38] there is an extensive database on this subject. Despite the existing general problems, research shows that wind projects actually rank near the bottom of the list of developments that negatively impact wildlife and the environment [36]. The author of the paper [37] provides compelling statistics on the annual mortality of birds in the United States of America due to various sources of energy and other factors. The wind energy sector accounts for a little more than 46,000 cases but fossil-fuel power plants account for almost 24,000,000. However, completely different factors cause the greatest mortality of birds - windows in buildings and cats. Here, bird mortality figures are around a hundred million. Nevertheless, in some cases, such statistics may not be convincing, for example, in the case of wind parks interfering with migratory routes, therefore, serious attention is paid to the study of these issues [39–42]. Various aspects of influence are considered, including administrative mechanisms (the requirement to take into account issues of impact on wildlife in the building permits issued), and in the engineering plan through an in-depth assessment of the terrain, arrangement of wind turbines, optimization of their work, etc. [39-42].

Wind energy statistics

Extensive statistics on wind energy both globally and regionally can be found in [45-50]. According to [45], installed wind power capacity in 2018 was 48,912 MW (an increase of 9.5% compared to the previous year), and the cumulative volume of wind energy in the world reached 563,659 MW. In 2017, wind power plants generated 1,134.5 TWh of electricity, and according to [46] – 1,128 TWh in 2018. Statistics differ in different sources. Thus, in [47], the volume of installed capacities in 2018 amounted to 48,820 MW, and the cumulative volume was 568,409 MW; an increase of 51 GW or 9.44%). The ratio of total installed capacities between onshore and offshore stations in 2018 was [53] 539,954 MW to 23,706 MW or 22.8 to one. Over the past decade the total volume of offshore wind farms has increased from 2,134 to 23,706 MW or more than 11 times [45]. The following values ​​are also given for onshore wind farms – 539,954 MW in 2018 and 147,988 MW in 2009 (an increase of more than 3.5 times). The distribution of wind power in the leading countries according to [45] is shown in Figures 20-21. The three world leaders in installed wind power facilities are China, the USA and Germany. In China, in 2019, the volume of newly installed capacities amounted to 43.8% (210,478 MW) of the global total.

Fig. 20-21. The ratio of the volumes of installed wind power capacities by country to the world leaders in 2019, % (left) and the ratio of the volumes of electricity generation by country to the world leaders in 2019, % (right)

Sources: Based on Data from  IRENA (2020),  Renewable  Energy  Statistics  2020, International  Renewable  Energy  Agency (IRENA), Abu Dhabi; BP Statistical Review of World Energy June 2020

The world leader in the number of installed offshore wind farms is the United Kingdom, with a share of 35% (Fig. 22) of the total installed capacities. Germany and China have 27% and 20%, respectively [45]. For several countries, wind energy is the main source of electricity production. For example, according to [45-46], the share of wind energy in electricity production in Denmark is approaching 50% (Fig. 23), and in Ireland and Portugal it accounts for around 20%. Only countries with total annual electricity production higher than 10 TWh were taken into account.

Fig. 22-23. The ratio of the volumes of installed offshore wind energy capacities of world leader countries in 2019 (left) and the countries with the largest share of wind energy in the total electricity generation in 2018 (with a total generation volume of at least 10 TWh per year)

Sources: Based on Data from  IRENA (2020),  Renewable  Energy  Statistics  2020, International  Renewable  Energy  Agency (IRENA), Abu Dhabi;
BP Statistical Review of World Energy June 2020; Danish Energy Agency; Sustainable Energy Authority of Ireland

Wind power plants

Currently, there are several thousand wind farms of various capacities installed throughout the world. More than a thousand wind farms are operating in the USA, China, Germany, Spain, Great Britain, France, Denmark and, possibly, India and Sweden. Detailed information on US wind farms is presented in [51-52]. A fairly large amount of data is available on Wikipedia, where one can find lists of wind farms both for individual countries and for some regions [53-57]. The most extensive database on wind energy, including individual wind farms, lists of companies participating in projects and characteristics of wind turbines is available in [58]. The map of the largest wind farms in the world with their technical and economic indicators is presented below.

Fig. 24. The world's largest Wind parks

   aenert_map_wind_energy [0.9 MB]

The majority of onshore wind farms, with an installed capacity of more than 500 MW, are located in the U.S., and the majority of offshore wind farms in the UK. The largest wind farm in the world is Gansu (Jiuquan) Wind Park located in north-western China with a capacity of 7,965 MW [59]. Its first phase, with a capacity of 5,160 MW, was completed in 2010. The Chinese authorities intend to bring the total capacity of this wind farm up to 20 GW [59]. Alta WEC (Mojave) I-IX with a capacity of 1,548 MW is the largest onshore wind farm in the United States and was commissioned in 2010. The turbine for this project was supplied by Vestas [60]. 1 197 MW Hornsea Project One (UK) is the largest offshore wind farm in the world. Here, the capacity indicated relates to only the first phase of this power plant, which is still under construction, but has already begun to supply electricity to the network. The total planned capacity of this wind farm is 6 GW [61]. More detailed information on current and planned wind energy projects can also be found either on these project’s websites, or on the websites of companies producing wind turbines, for example, [62-64].

                  Pinyon Pines wind Farm, California, USA, 56 turbines: Vestas V90/3000 (power 3 000 kW, diameter 90 m)

Major companies

Wind energy is an intensively developing and high-tech industry that requires the involvement of a large number of companies specializing in a highly diverse area of modern industry. This is partly due to the complexity of the wind turbine itself, an intricate unit consisting of many components. In addition, high towers, large-sized rotors and gearboxes, generators, electrical converters and others, although they are components of a predominantly standardized production, have many individual characteristics depending on the overall design of the wind turbine, which predetermined the formation of a substantially new industry. At the same time, the large-scale production of wind turbines has been commenced in many countries of the world, where in a relatively short time many new jobs have been created and several large companies have been established.

Lists of companies involved in wind energy can be found in directories of legal entities issued in each country. Information on the largest manufacturers can be found, for example, in [58,65,66]. A large number of regional companies interested in expanding their production can be seen on the lists of participants in international exhibitions, for example, in [67-69]; important when looking for business partners, especially in unfamiliar markets.

Some companies in the wind energy market are public and place their shares on various exchanges. Fig. 25 depicts the change in the stock price of some of their shares over the past ten years.

Fig. 25. Dynamics of change in the exchange value of shares of some public companies producing wind turbines against the background of the NASDAQ Composite index

After the financial market crisis in 2008 the value of shares dropped significantly, and only three companies - Vestas, Goldwind and Siemens Gamesa managed to maintain their levels of profitability. However, as can be seen from the diagram, the index of high-tech companies NASDAQ Composite during this time has grown significantly more.
According to most sources, the largest manufacturer of wind turbines in the world is the Danish Vestas. At the time of writing, the company's website reported that the total installed capacity of the company in the world exceeds 105 GW or 17% of global capacity [70]. The company's products are found in 80 countries, with employees totaling almost 25,000. Founded in 2014, MHI Vestas Offshore Wind specializing in offshore wind turbines and a subsidiary of Vestas Wind Systems A/S and Mitsubishi Heavy Industries Ltd [71] have designed a powerful turbine V174-9.5 MW™ with the largest commercially-proven rotor size – 174 meters and with a swept area of 23,779 m2. The portfolio of confirmed orders of this company is more than 330 turbines with a total capacity of more than 3000 MW.
Siemens Gamesa, operating in approximately 90 countries, has more than 80 GW of installed onshore facilities and another 12 GW of offshore wind turbines [72]. The company’s turbines are highly reliable, highly automated and efficient. The company has developed the largest floating wind turbine – Siemens Wind Power SWT-6.0-154 - with a capacity of 6 MW, with a rotor diameter of 154 m and a height of 101 m, which are successfully operating in Scotland.

Another major supplier of wind turbines is the American company General Electric. The capacity of their onshore wind turbines ranges from 1.7 MW to 5.3 MW [73]. The company has installed more than 40,000 land-based wind turbines in more than 35 countries with a total capacity of 62 GW [73]. The company's flagship product, and one of its latest developments, is the Haliade-X offshore wind turbine with a tower height of 260m above sea level, a rotor diameter of 220 m, a blade length of 107 m each, which is capable of generating 67 GWh of electricity annually and has a unique capacity factor of 63% [5].

The largest manufacturer of wind turbines among Chinese companies is Goldwind. Their global installed capacity exceeds 50 GW with more than 30,000 wind turbines in 24 countries [74].
The German Enercon, with nearly 28,000 MW of installed capacity globally, occupies more than 50% of the market in Germany and 23% in Europe [75].
Other major manufacturers of wind turbines often mention Nordex SE (Germany), Acciona (Spain), Senvion (Germany), Sinovel (China), Suzlon (India), Envision (China).

Research and innovations

Research and innovation activity in wind energy has increased many times over the past ten years and may have peaked. This review presents the results of an analysis of more than 10,000 scientific papers and about 20,000 patent applications published in the world over the past period. The analysis methodology can be found at the Advanced Energy Technologies website. The authors of the scientific works mentioned were about 4000 researchers from more than 100 countries and almost 700 scientific organizations. Patent applications were submitted by almost 3,000 applicants from 48 countries in more than 50 patent offices worldwide. Clearly, this is not a complete collection of the results of scientific research and engineering, however, it is representative enough to identify existing patterns and directions of innovation. Complete lists of WIPO scientific papers and patent applications mentioned in this review, as well as detailed statistical patent reports, can be found at the Advanced Energy Technologies website.
Below are some statistical results of the analysis, including comparative charts on the main indicators of patent applications and scientific publications.

Fig. 26-27. Distribution of the number of patent applications by the most frequently mentioned keywords (left) and by belonging to the corresponding class of technological elements (right), 2009-2018

Source: Advanced Energy Technologies

“Wind turbine" is the most frequently cited term in the titles of documents or in their English translations, among other very common terms. Among the technological elements related to the main components of the wind turbine, the greatest number of registered patent applications concerned the control and management systems, and the blades. In both cases, the peak value of applications was recorded in 2015. Figure 28 shows a diagram of the distribution of patent applications among the main patent offices of the world on subjects affecting technologies and equipment for wind energy.

Fig. 28. Top-10 patent offices registered the largest number of patent applications in 2009-2018 for wind energy

Source: Advanced Energy Technologies

The most popular offices for inventors were the US Patent Office (USPTO) and the European Patent Office (EPO), each comprising about 20% of all patent documents reviewed. About 15% of applications were filed with China Patent Office (CNIPA). It should be noted that these three regions are currently the leaders in the number of installed wind turbine capacities (Fig. 21). About 13% of the total number of applications were registered with WIPO, and about 11% in other offices outside the top ten.

Fig. 29-30. Top 10 countries whose residents registered the largest number of patent applications and published the largest number of scientific papers in 2009-2018. Patent applications on the left, scientific publications on the right.

Source: Advanced Energy Technologies

Inventors from Germany registered the largest number of patent applications for this period – more than 36% (Fig. 29) – followed by representatives of Denmark (a little over 21%) and the United States (13%). The top 10 countries also included Japan, Spain, China, the United Kingdom, the Netherlands, France and South Korea. The remaining countries accounted for about 7.6%.
It is important to identify the main areas of research and engineering from the point of view of solving the existing technical, administrative or environmental problems in wind energy. The result of such an assessment is shown in Fig. 31-32.

Fig. 31-32. Distribution of patent applications and scientific publications on wind energy. Patent applications on the left, scientific publications on the right.

AOP - Administrative and organisational problems; ESI - Environmental and social impact; HOR - High OPEX / Repair and replacement; HCC - High CAPEX / Plant construction; HOM - High OPEX / Operational maintenance; HCP - High CAPEX / Equipment production; HCG - High costs in general; LES - Low efficiency of secondary equipment; LEN - Low efficiency caused by secondary natural factors; LEKM - Low kinetic-to-mechanical power conversion efficiency; LEW - Low efficiency caused by wind variability; LEG - Low efficiency in general; LEME - Low mechanical-to-electric power conversion efficiency; UP - Unclear problem
Source: Advanced Energy Technologies

There is a significant difference between the primary interests of inventors and authors of scientific papers. If the representatives of the first group were more focused on solving the problems of High OPEX/Repair and replacement, High CAPEX/Plant construction, High OPEX/Operational maintenance, etc., the authors of scientific publications had a considerable interest in the issues of Administrative and organizational problems, Low efficiency caused by secondary natural factors, and Low efficiency of secondary equipment.
A similar trend is observed when considering the authors' interest in the elements of technological equipment and the corresponding technological processes in wind energy (Fig. 33-34).

Fig. 33-34. Distribution of patent applications and scientific publications by the main elements of technological equipment and applied operations in wind energy considered by the authors in published documents. Patent applications on the left, scientific publications on the right

AC - Aerodynamic casings (nacelles, shrouds, etc.); B - Blades and components thereof; CSS - Control and safety systems; EE - Electrical equipment and generators; ESH - Energy storage and hybrid generation systems; GT - Gearbox and transmission; MRR - Maintenance, repair and replacement; OTE - Other technology elements; R - Rotors and components thereof; SE - Structural elements
Source: Advanced Energy Technologies

Control and safety systems were the focus of inventors.  The authors of scientific publications concentrated on Other technology elements, Control and safety systems and Electrical equipment and generators (Fig. 33-34).

By combining the information in Fig. 31-34. It can be determined that the largest number of patent applications addressed the issue of Repair and replacement for Control and safety systems and Blades. In scientific publications, the combination of Operational maintenance and Administrative and organizational problems is most often found in combination with Other technology elements or Control and safety systems.

Tables 2 and 3 show the top 10 applicants by the number of patent applications and the Top 10 organizations by the proportion of published scientific papers in the field of wind energy in the considered sample of documents for the period from 2009 to 2018.

Table 2. Top 10 applicants by the number of patent applications in the field of wind energy for 2009-2018

StatusCountryNameVolume ratio, %
CompanyDKVestas  Wind Systems A/S13,75
CompanyDEWobben Properties GmbH12,60
CompanyDESiemens AG8,39
CompanyUSGeneral Electric8,11
CompanyJPMitsubishi Heavy Industries, Ltd.3,84
CompanyDKLM WP Patent Holdings A/S2,38
CompanyDERepower System AG2,02
PersonDEWobben Aloys1,91
CompanyESGamesa Innovation & Tachnology S.L.1,65
CompanyDESenvion S.A.1,40

Source: Advanced Energy Technologies

Table 3. Top 10 organizations in terms of the proportion of published scientific papers in the field of wind energy for 2009-2018

StatusCountryNameVolume ratio, %
OrganizationCNNCEPU North China Electric Power University5,3
OrganizationUSNational Renewable Energy Laboratory (NREL)2,7
OrganizationDKTechnical University of Denmark (DTU)2,6
OrganizationNONorwegian University of Science and Technology (NTNU)1,9
OrganizationDKAalborg University1,7
OrganizationCNShanghai Jiatong University1,6
OrganizationCNChina Electric Power Research Institute1,3
OrganizationCNCQU Chongqing University1,3
OrganizationCNTHU Tsinghua University1,2
OrganizationCNXinjiang University1,2

Source: Advanced Energy Technologies

Development trends

Assessments of existing trends in the development of wind energy and the formation of development forecasts are important for businesses, investors, and also for taking into account climate change. Below are several works that assess the prospects for the development of wind energy up to 2050.

The forecast of the long-term development of wind energy under various scenarios (Development of Long Term Wind Market Projections) are presented in [76]. In total, four forecast options were considered in this paper: IEA New Policies scenario, IEA 450 scenario, GWEC Moderate scenario, GWEC Advanced scenario. In particular, the mid-IEA 450 scenario is based on World Energy Outlook 2015 / IEA and determines the energy path in order to have a 50% chance of limiting the global increase in average temperature to 2oC / 450 ppm carbon dioxide equivalent (about a 50% chance of limiting the global increase in average temperatures up to 2oC / 450 ppm carbon dioxide equivalent).
According to this work on the IEA 450 scenario, the total wind power in the world will be: in 2020 – 658,009 MW, in 2030 – 1,454,395 MW, in 2050 – 3,545,595 MW, which implies a more than five-fold growth between 2020 and 2050, and between 2020 and 2030 – more than double. In the latter case, according to the authors of the IEA 450 scenario, the largest contribution to development will be made by: China – more than 235 GW, North America – more than 170 GW, OECD Europe – almost 165 GW and India – almost 90 GW.

A forecast for the development of wind energy in Europe until 2030 was proposed in [77]. The paper considers three scenarios - low scenario, central scenario and high scenario. According to the authors, by 2030, the share of wind energy in electricity in Europe will be 21.6, 29.6 and 37.6% for the low, central scenario and high scenario, respectively. It is assumed that in this case the total power will reach 256, 323 and 397 GW in the same sequence of consideration. For the central scenario in 2030, the largest volume of installed onshore capacities will be 70 GW in Germany, and the top ten countries in addition to Germany will include: France (36.36 GW), Spain (35 GW), Great Britain (15 GW), Italy (13.6 GW), Sweden (12 GW), Poland (10.5 GW), the Netherlands (8 GW), Portugal (7 GW) and Austria (6.7 GW). According to the authors, the top three leaders in terms of offshore capacity will be Great Britain, where 22.5 GW will be installed, Germany -15 GW and the Netherlands – 11.5 GW. For some countries, the share of wind energy in total electricity production will exceed 50%. Among them – Denmark – more than 70%, Ireland – almost 70%, Estonia – about 60%, the Netherlands –about 50%.

In the second half of each year in the U.S., the Energy Information Administration traditionally publishes its International Energy Outlook, which examines in detail the development of energy in the world until 2050. In the review for 2019 [78], the following forecasts are presented regarding wind energy (Net electricity generation, trillion kilowatt hours): 2020 - 1.73, 2030 - 3.17 and 2050 - 6.7. By 2050, according to this forecast, the share of renewable sources will account for almost half of all global electricity production, where the share of wind energy will be a little more than 30% of all renewable sources, including hydropower. In the OECD countries of Europe, the production of electricity from wind energy from 2020 will increase from 0.5 to 1.25 trillion kilowatt hours by 2020 and will amount to about 25% of the total of all sources of generation. For India, these indicators are projected as follows – an increase from 0.11 to 1.42 trillion kilowatt hours and also about 25% of the share in 2050, for China – 0.52 and 2.27 trillion kilowatt hours and a 17% share of wind energy in the total generation in 2050, respectively. The forecast for the development of wind energy in the United States is presented in [79]. A fundamentally different trend is assumed there - the main growth will be limited to the period from 2018 to 2021, after which it will significantly slow down due to the expiration of the tax benefits. The total increase in electricity generation is expected from the level of 0.32 trillion kilowatt hours in 2020 to 0.37 in 2030 and, finally, to 0.43 trillion kilowatt hours in 2050 with 134.7 GW of installed capacity (for the Reference case)).

Fig. 35-36. The most intensive development of wind energy is forecasted to happen in the Chinese market

A detailed forecast for the development of renewable energy, including wind energy, is presented in [80]. Two development options are considered – Reference case and REmap Case. In the latter, most dynamic version, the forecast takes into account the introduction of low-carbon technologies and the intensive increase in energy efficiency in order to limit global temperature to below 2oC. At the same time, it is planned to increase the world's wind power capacities from 411 GW in 2015 (399 GW - onshore wind farms, 12 GW - offshore) to 5,445 GW (4,923 GW – onshore wind farms, 521 GW - offshore). With an estimated total electricity generation in 2050 of 41,508 TWh, the share of wind energy will reach 36%.

The development trends of offshore wind energy were proposed in [81] and, in particular, for floating wind turbines in [82]. Between 2010 and 2030, offshore capacities are expected to grow by 24.5% a year, with 58% of installed capacities concentrated in Europe, 23% in China and 20% in the United States [81]. Also, by 2030, the total installed capacity of floating turbines will be a little more than 4,000 MW [82].


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