In the face of increased environmental awareness and the concept of going green, efforts towards conserving the environment is only possible through investment in highly effective renewable energy sources such as the coastal wind turbines. Wind energy has for a long time been exploited to perform various functions including machine operation, water pumping and electricity generation. While the use of wind energy has been utilized for many centuries, modern day use has exhibited a trend that could see wind energy become the world's preferred source of energy. Most countries have dedicated huge sums of money towards the development of wind energy projects to support their citizen's electricity and power needs. As a matter of fact, various countries including the UK are committed towards ensuring that wind energy is used to light every home without the need for an additional source of energy.
In late November, the government of the Netherlands authorized a 700 million Euro project to start off the West Rijn wind farm in the North Sea. This farm was expected to produce 284 megawatts in terms of capacity; enough to supply electricity to 150,000 to 200,000 homes every year. This was just a pilot project and the Dutch government is determined to achieve 6,000 megawatts by the year 2020. The case of the Netherlands is a mere reflection of what many countries propose to achieve in the next few years. The United Kingdom for example is bent on ensuring that every home is lit by offshore turbines by the year 2020. In the Unites States, the number of offshore wind farms is rising by the day. Canada on the other hand has set up various wind farms including Trillium Power Wind 1 which is estimated to produce over 400MW. Perhaps the greatest motivator in these investment decisions lies in the low costs associated with wind energy. While the initial setup may be costly very minimal costs are needed for the operation of wind farms such that energy expenditure could be highly subsidized in the long-run. Other advantages including the fact that wind is a natural and renewable source of energy and that it does not endanger the environment may also be attributable to the increased use of wind energy.
The use of coastal turbines as a source of wind energy has led to interminable debates; most of which point out the huge initial capital outlays and environmental conservation which includes discussions on the danger of electric poles to the marine animals. Coastal turbines are also technically difficult to manage. The reliability of wind is highly doubted due to the fact that wind does not always blow optimally to allow the collection of maximum wind energy. Further, concerns on the effect that coastal turbines have on the scenery at the coasts have been raised due to the possibility of affecting the tourism sector.
The bottom line however is that coastal wind turbines not only have the potential to collect huge volumes of energy but they are also suitable in eliminating noise pollution that is expected at onshore wind farms. It has also emerged that bulky water turbine component such as nacelles, tower sections and blades are easier to transport over water as compared to the land. Further, offshore wind projects are likely to create more jobs as compared to onshore projects due to the complexity of work involved in their construction. This paper seeks to navigate the utilization of coastal turbines as a source of energy with a view of establishing the limitations of using this method and further seek recommendations to correct or improve the process of collecting wind using costal turbines. The newly proposed technology of the use of a supergrid to connect many wind farms with an aim of stabilizing electricity supply is given special emphasis. It is a competent solution to the current challenge of intermittency and could result in a major breakthrough as far as the use of wind as a permanent source of energy is concerned.
Background of the study
Given the growing popularity of green energy, the use of wind is ranked among the best alternatives of renewable energy. The method has been utilized in many countries in the world including the US, UK, Denmark, German, Spain, France and the Netherlands among other countries. While wind energy's potential has not been optimally utilized, one can easily observe that the development of wind energy and more so in the establishment of offshore wind farms is on the rise. Wind energy could actually be the sole source of energy for some countries in the next few decades. There are numerous advantages associated with wind energy hence the reason for the rapid adoption as an alternative source of energy.
To begin with, wind is a renewable source of energy; given that wind is available in the atmosphere all the time. This is unlike coal and petroleum which could be completely depleted in future as they cannot be replaced. Wind also has an advantage over nuclear sources of energy whose by-products could be harmful to the environment and which has to be constantly protected to protect citizens from terrorist threats. Besides the initial cost, wind power could be very affordable in the long run and even turn out to be a free energy source. Wind turbines usually occupy less space as opposed to average power stations. Furthermore, turbines are often placed in remote areas such that they do not occupy usable land masses. Even in cases where turbines occupy productive areas, the land can still be used for other purposes such as agriculture. Wind turbines provide a unique source of energy for remote areas and mountainous countrysides where ordinary electricity supply has not been installed. This is because small turbines to fit the needs of the area can be easily designed.
History of wind energy
The concept of wind power is not particularly and it could be as old as human beings have been in existence. The art of sailing, grain winnowing and drying of clothes can all be linked to the power of wind. Later developments involving the use of wind-powered machines to pump water and to grind grain also signify that wind power has been in use for a long period of time (Khan, 2006). The development of wind energy for use in providing electric power and running industry was however an important milestone in the utilization of wind energy.
There are indications that windmills were used in China and Babylon as early as 2000 to 1700 B.C to grind grains and pump water. Over 5,000 years ago, Egyptians used the power of wind to sail ships (Khan, 2006). The use of windmills to grind grains in 17th century AD was also evident in Persia and Afghanistan. In the 12th century, Europeans imported the windmill technique and used it in the development of the horizontal axis windmill which became very famous up to the 18th century when James watts introduced the steam engine. The use of wind power later declined in the 20th century due to the availability of cheap hydropower and reliable fossil fuels. Even then, the first electric power generation from wind was proposed in Denmark, resulting in the production of numerous aero-generators mostly in Europe. It was not until the 1980s that wind turbines were engineered on an industrial scale. Denmark, Netherlands and the United States were among the first few countries to experiment with wind turbines. The first wind farm in the world was actually set up in December 1980 in Southern New Hampshire. It consisted of 20 turbines and had a capacity of approximately 30 kilowatts. More wind farms followed in later years; mostly small turbines whose power range averaged 100kW.
A renewed interest in wind energy was observed in 1973 following the oil crisis and by 1980; large scale wind energy systems with modern designs and incorporating microelectronics control and monitoring were introduced. With increased improvement in turbine design, the cost of producing energy through wind reduced significantly and the outcome was more desirable. By the beginning of the 21st century, there was a growing concern over energy security, depletion of non-renewable resources and global warming among other environmental issues. The steady rise in prices of oil after 2003 was also alarming and the need to take urgent action was imminent. As a result, there was a robust growth in renewable energy sources including solar energy, biomass and wind energy. In the period following the oil crisis, many industries had turned to using coal and natural gas as a substitute for petroleum. Unfortunately, natural gas started experiencing supply problems such that wind power was generally considered more reliable in electricity generation than natural gas. The use of wind energy has been growing steadily and many wind farms have been set up mostly in Denmark, the US and Germany. Most recently, coastal wind turbines have become famous sources of wind energy due to their proximity and potential to generate high levels of energy.
Rationale of wind power generation
Environmental conservation efforts have triggered the adoption of renewable sources of energy with an aim of reducing pollution and conserving non-renewable energy. Subsequent studies have indicated that global warming is being facilitated by pollution resulting from industries and electricity production plants. The ozone layer is therefore at risk of being depleted; an occurrence that would lead to the penetration of harmful rays from the sun leading to skin disorders. As a result, environmentalists are continuously encouraging the creation of environmentally friendly energy production. According to the American Wind Energy Association, wind energy that is being currently used could produce electricity that is equivalent to that produced by 90 million oil barrels or 30 million tons of coal (Provey, 2009). Unlike coal however, wind energy does not pollute the environment through the release of carbon monoxide, mercury and other harmful substances that could ruin the environment.
Besides the initial costs involved in the establishment of wind farms, wind energy is a low cost alternative that could save millions of dollars if the use of wind power is used worldwide. As noted by heath (2007), wind energy can be produced at below 10 cents per kilowatt hour. Furthermore, there are no costs involved in obtaining wind as it is freely available in the environment. As a result, a country could find itself producing energy at zero costs thus reducing the cost of energy.
As population levels continue to rise, there is dire need to preserve land in order to utilize it for useful economic activities. The use of turbines to collect energy occupies minimal space and in most cases wind farms are located in remote areas where economic activity may not be viable. Deserts, mountainous areas and coastal areas can barely be used for economic activities such that turbines do not affect the availability of land. This is unlike other energy generation activities such as geothermal electricity, nuclear electricity and other forms of electricity that occupy large tracts of land which could otherwise be productive such as river banks. It is also notable that in the case of wind turbines, the wind farm can still be utilized for other purposes at the same time such as for agriculture purposes.
Coastal wind turbines as a source of wind energy
The use of coastal wind turbines is gradually gaining popularity as an effective technique of collecting wind power. This is attributable to the open air spaces that allow wind to flow freely without interruption as in land turbines. The method however has a number of disadvantages which have led to unrelenting debate with environmental conservation activists referring to the method as costly and destructive. Nevertheless, the use of coastal wind turbines has proved more economical than the use of onshore turbines due to their large production capacity. As noted by various researchers, the initial costs are eventually balanced by the high energy capacity produced and the consequent low costs associated with wind energy. The use of coastal wind turbines can therefore be considered viable.
Origin of coastal wind turbines
Mature wind turbines available in the 500/600kW class enabled the initial use of offshore wind turbines in Germany. This was in the late 1980s where demonstration was made using miniature offshore test units (Hau, 2006). In 1991, the pioneer offshore wind farm was set up in Denmark off the Lolland coast, near Vindeby. The tiny wind farm consisted of 11 turbines which were positioned in water between 3-4 meters in depth. Each turbine had a power output of 45kW. The turbines were located at a maximum distance of about three kilometers from the coast. The stated cost for the project was 76.2 million Danish Krones; an investment cost that builders estimated to be double the amount required to set up a similar project located on the land. More demonstration projects were executed in the following ten years in locations in Denmark, Sweden and Holland. These projects bore almost similar features namely: 3 to 10 meters water depth, a distance of up to 6 kilometers from the coast and 500/600 kW class wind turbines that were slightly modified. Coastal turbine technology
Offshore turbines have unique technical needs as compared to onshore turbines due to the severe climatic and environmental exposure that such turbines are subjected to. The turbines look similar to the normal wind turbines but are slightly modified. The towers of offshore turbines are strengthened in order to withstand the wind-wave interactions and hence avoid premature damage. Offshore turbines must also be furnished with corrosion protection, high-grade exterior paint, internal climate control and integrated service cranes. In order to minimize the cost of servicing, coastal turbines need to be fitted with automatic greasing systems such that the blades and bearings can be easily lubricated. This is accompanied by pre-heating and cooling structures aimed at ensuring that gear oil is maintained at narrow temperature ranges. Another factor to consider is lightening protection such that coastal turbines need to be fitted with lightning protection systems to reduce the potential risk of damage. Coastal turbines need to be equipped with aerial warning lights so as to ensure that they do not interrupt navigation. While the upper sections of coastal turbines are painted grey of light blue so as to allow them blend easily with the sky, the lower sections are often painted using bright colors such as yellow in order to aid navigation and to make the towers more visible to passing vessels.
Typically, coastal turbines are definitely bigger so as to maximize on the steady offshore winds and thus create an advantage of economies of scale. Offshore turbines mostly have towers that are larger than 200 feet as opposed to the 60 to 80 meters in ordinary turbines. While offshore turbines have a 250 to 350 feet rotor diameter, normal onshore turbines would have blades measuring 30 to 40 meters long. This not only maximizes the strength of offshore turbines but also ensures that the maximum amount of wind energy is trapped.
Modification of coastal turbine technology is also highly necessary in the collection and transmission of the generated energy. Coastal wind energy is harvested from undersea collection cables connected to multiple turbines. Electricity is transported from the cables to a transformer which then converts the generated electricity into high voltage before transmitting it to an onshore substation through undersea cables. It is from the substation that the electricity is transferred to an onshore electricity grid for distribution to users.
Electricity production using coastal turbines
Once the developers have identified a suitable location, piles are introduced into the seabed. The piles provide support to the other components on the turbine. A tower and a support structure are needed to support each turbine as well as a sheltered access platform for the personnel. The turbine, which is essentially composed of a three-bladed rotor that is connected to the generator via the drive train, is assembled. Once it is fully connected, the nacelle is turned towards the direction of the wind by the direction sensors in order to collect the maximum wind energy. The nacelle is a shell that houses the generator, gear box and the blade hub. Wind moves over the blades making them rotate around a hub that is linked to a shaft within the nacelle. Through the gear box, the shaft powers a generator which in turn converts the collected wind energy into electricity. This electricity is transmitted it to an onshore substation through undersea cables. From the substation, the electricity is transmitted to an electricity grid which distributes the electricity to the users accordingly. Merits of coastal wind turbines
Despite the reduction in electricity costs associated with wind energy, it is notable that wind turbines are totally noisy. Accordingly, coastal areas are suitable locations for wind turbines; given that there is limited inhabitation in these areas. They are less obstructive because the distance from the shore tends to mitigate their size and the noise that they make. Offshore wind turbines are often constructed at least 8-10 kilometers from the shore such that the limitation of noise is barely present in these types of turbines.
It has been established that the overall mount of wind power that is economically extractable is substantially higher than the human power presently being used from all power sources. The estimate wind power energy that is economically viable is 72 terawatt (TW). This is considerably high in comparison to the 15TW representing the average power consumption of the entire globe. Unfortunately, the energy in flowing wind cannot be fully recovered such that the intensity and consistency of wind is highly important as far as wind power generation is concerned. Indeed, it is impossible to trap the entire wind power flowing at a given point. Notably, the amount of energy recovered is highly dependent on the intensity of the wind. Continuous wind movements with a speed of over 160km/h are considered viable for effective energy collection. Finding uninterrupted streams of wind is nevertheless challenging due to obstacles that are likely to exist such as mountains, trees and building among other barriers. According to Khan (2006), surface friction owing to resistance of different elements in the face of the earth such as trees tends to affect the speed of wind by causing turbulence which greatly reduces the speed of wind. The open ground at coastal areas therefore provides ideal locations for the collection of wind energy; given that winds blowing from the ocean or sea do not encounter any obstacles thus enhancing the creation of more energy. The surface roughness on water is less than that on the land such that wind speed is more considerable over open water. The use of coastal turbines to produce energy is therefore quite effective in increasing the amount of wind power that is converted to energy.
The transport of wind turbine components often proves difficult because of the underpass clearances and turn clearances that trucks on land have to negotiate during the transport of turbine parts. Furthermore, trucks limit the size of components that may be transported unlike offshore where such parts can be moved by barge. In the offshore areas, there is no need to overland high-voltage lines and there are fewer visual and zoning issues (Provey, 2009). It is also notable that the large constructions cranes may have difficulty in accessing land wind farms which are often constructed in remote areas or in rocky and mountainous regions. Crane vessels can be easily moved over water such that the construction of offshore turbines is likely to be easier.
Job creation is another merit of coastal wind turbines. Although not directly related to the energy sector, job creation is important for the economic well-being of a nation. The construction of coastal wind farms is definitely labor intensive and a significant number of personnel are required to work at the site during the construction and also provide maintenance services after the project is complete. In the US for example, 100 jobs will be created during the manufacture of pilings meant to anchor Cape Wind's project.
Demerits of coastal wind turbines
Despite the viability of coastal turbines in providing alternative energy in a world where environmental conservation is highly emphasized, experts maintain that the investors must be highly cautious of the risks that such projects are likely to carry. Coastal wind energy projects not only require huge capital outlays but they also present major technical challenges during construction such that they are very risky for the investors (Harris, 2010). The maintenance of a costal wind farm is also very costly and operational problem such as gearbox failures may prove difficult to correct especially during the winter. Harris notes that the problem is no longer about the identification of the market from wind energy but the uncertainty in the technical and financial implementation of the projects.
Engineering challenges in the installation of coastal turbines remain a major limitation when investing in coastal areas. Harris (2010) describes the challenges as more complex than those of the offshore gas and oil industry established in the 80s. Furthermore, coastal turbines are bound to take long periods of time to engineer and install due to the process of establishing their sustainability in the water.
There are environmental considerations as far as the installation of coastal turbines is concerned. Various issues have been raised regarding the effect on the ecosystem and how this is likely to impact on marine animals and birds. It is believed that coastal wind farms could lead to an increase in fish population around the area due to the constant supply of food from the constructors and maintenance team. This may in turn encourage bird population in the area thus leading to collisions between birds, rotors and towers. This could highly affect the efficacy of a wind farm. It is also notable that wind turbines could disorient the navigation patterns of birds and marine animals. This results from tower illumination and from electromagnetic fields that result from the erection of electric cables. These cables are also bound to cause vibrations and noises underwater; all which could affect the marine animals' navigation ability. Furthermore, anchoring devices, support pilings, electromagnetic fields and scour-protection materials alter natural environments and could endanger the animals' migration patterns.
The establishment of coastal wind firms could lead to extinction of ancient economic activities which may have been considered a culture in a particular country. The offshore wind farm that could be established at Grimsby, UK could replace fishing; an industry that is considered to be the most famous. There are plans to construct 5,500 wind turbines at the country's east cost by the year 2025. This farm could be capable of providing 25,000 jobs and 20% of UK's power but nevertheless, it will ruin an economic activity that was probably ingrained in people's culture.
Wind turbines greatly distort the scenery and are often considered unsightly when constructed in the coastal areas. The visual impacts result from rotating turbine blades to aerial warning lights are identified as potential distortions to the coastal scenery. This could affect economic activities such as tourism or fishing activities associated with such areas.
The future of wind energy from coastal turbines
The stability of global climate, environmental conservation and potential for redressing the current shortages in energy will require a great deal of investment in renewable energy sources. The use of coastal wind turbines in trapping wind energy remains one of the most effective strategies in the achievement of these goals. This denotes that investors around the world must continually invest in wind energy production in order to reduce the dependability on non-renewable sources of energy. Archer and Jacobson (2007) note that theoretically, world's demand for electric power which amounts to approximately 1.6 to 1.8TW could be satisfied by 890,000 turbines with blades measuring 126m in diameter and having a capacity of 5MW. The speed of wind is estimated at 8.5m/s or faster and an allowance of 10% is reserved to account for lost energy. They further note that this number of turbines is about 7-8 times the number of total turbines that have been installed in the world so far such that it may not take a long time to achieve such a goal. The most significant barrier for large-scale implementation of wind power remains the intermittent nature of winds. Sudden fluctuations in the flow of wind almost defeat its predictability and reliability of wind as a sustainable energy source. This significantly reduces its marketability hence the reason why wind energy has not been undertaken as a large scale venture in many parts of the world. This also insinuates that for wind energy to be effectively used as a source of power, new technologies must be introduced in order to conveniently trap wind energy.
Mitigating the intermittency of wind (The supergrid proposition)
Indeed, wind energy has been considered unreliable; with the justification that the wind will not always blow. This insinuates that even where large wind farms are erected, a convectional back-up capacity must be kept stand-by for the days when the wind will not blow. This issue has led to the proposal of the creation of a 'supergrid' that can connect all the grids within a specific area so as to reduce the need for backup capacity. The supergrid would ensure that even if the wind is not blowing in a certain location, wind energy originating from another area can still be used to supply energy there. This proposal was initially proposed to serve Western Europe and is still being negotiated. In this proposal, national grids across Western Europe including Spain, France, Denmark, England, Ireland and the Celtic Sea should be joined by a supergrid. The core of this idea is that while it is true that wind may not blow everywhere all the time, it will not fail to blow somewhere. Consequently, the need for backup may be completely eliminated in the long-run. Implementation of the proposed solution would mark a milestone in the development of wind energy and could eventually eliminate use of environmentally unfriendly fuels in the production of energy and power.
In a study conducted by Archer and Jacobson (2007), it was concluded that interconnection of wind farms would play a great role in reducing transmission requirements and supplying baseload power. Archer and Jacobson note that baseload power has not been supplied using wind energy and that that through using a transmission grid to interconnect wind farms, a reliable energy source can be created. Once an array of interconnected farms is created, the correlation of wind speed among sites is lowered significantly such that the same wind regime is experienced in all sites at the same time. The array indeed operates like one single farm emitting steady wind power. A significant benefit emanating from the interconnection of wind farms is long distance transmission from a single location is enabled thus saving on costs; From a single that electricity can be transmitted for longer distances
The number of farms in each grid needs to be regulated in order to ensure that optimal wind production is achieved. In the study by Archer and Jacobson (2007), it is established that the marginal benefits of pooling the wind farms together reduced with the increase in the number of farms. This essentially means that despite the improvement in nonlinear parameters, the incremental benefits associated with the addition of new stations are bound to decrease. The conclusion of their study indicated that interconnection of wind farms could enable the world use consistent supply of electricity from wind and hence solve climate and energy problems. This could be the case in the proposed European Offshore Supergrid being undertaken by Airtricity Company to enhance wind power supply in the EU.
Floating wind turbines
The newest technological advancement in the use of coastal wind turbines is the emergence of floating wind turbines. This development is still under study and could be implemented if the results are considered viable. In a study labeled Project Deepwater performed in the UK by Energy Technologies Institute, it was established that the floating turbines were better placed in accessing stronger and consistent winds further into the sea. While the costs are initially high, long-term benefits are likely to be rewarding as the turbines will result in higher outputs thus lowering the overall cost of energy. Studies on the floating turbines are still underway. Another example is the Nova project which aims at establishing the effectiveness of vertical axis wind turbines. On the other hand, the Hel Wind Project is investigating the viability of changing the basic design used in constructing wind turbines.
Examples of major coastal wind farms
Rodsand II, an offshore project sponsored by the Danish government, is the newest and one of the biggest offshore wind farms in the globe. The farm which was launched in October 2010 has an installed capacity of 207MW and is made up of 90 2.3MW turbines erected in about 35 square kilometers. The turbines' rotor blades are 93 cm in diameter while the height of the hub is 68.5m. The farms onshore cables connect to SEAS-NVE Energy Company's grid. As would be expected of such an expansive farm, the capital outlay from this project amounted to €400 million which is equivalent to $554 million. Rodsand II is expected to provide 200,000 Danish households by producing 800 million kilowatt hours every year.
The Belwind Wind Farm which is still under development will consist of 110 turbines of 3MW each. The project which is located 46 km from the Belgian coastline was financed by European Investment Bank (Shahan, 2010). This project is being conducted in two phases and the first phase began in August 2009 to end within a span of 19 months. This farm introduces an improvement in the construction design of offshore turbines by making use of V90 turbines. These are light turbines which can allow turbines to be built on monopile such that the use of concrete gravity bases and jacket foundations will be avoided.
The Grimbsy offshore project is among the most ambitious wind farms to be constructed in the near future. This farm will have a capacity to provide 20% of UK's power needs through the construction of 5,500 wind turbines by the end of 2025 (Stuart-Cook, 2010). The first stage of installing 600 turbines is already complete. The coordinators of the project are seeking to benefit from the 100-billion pounds that has been dedicated by the government towards the development of offshore wind power by the end of 2030. Although the project threatens the fishing industry by occupying fishing waters, it hopes to create 25,000 jobs and also reduce energy expenses in future.
Denmark is currently undertaking a major project that is intended to eventually produce over 1000MW. The sites need to be built with 150MW each in the initial phase. These sites will then be evaluated and the experience used to advance the projects step by step until they reach their maximum intended capacity of over 1000MW for each site in the year 2030 (Hau, 2006). The achievement of this goal will see to it that Denmark can cover 40 to 50% of the total power consumption in the country using offshore wind energy alone. Two projects were started in Rodsand at the Baltic and Horns Rev in the coast of North Sea. Horns Rev became the first one to be completed in 2002. The experience however portrayed signs of unreliability resulting from severe technical malfunctions. To begin with, the salty environment was not conducive for the generators and transformers such that they had to undergo a comprehensive retrofitting procedure (Hau, 2006, p. 624).
Conclusion
Coastal wind turbines are bound to the most popular turbines for harvesting wind energy in the near future. This discussion establishes that despite the high initial fixed costs required during installation, such costs will be spread over the turbines' ability to produce more energy; leading to a significant reduction in average costs. This insinuates that countries that invest in wind energy will have minimal costs in future since sourcing the wind does not involve any financial obligation. A significant number of advantages in the use of coastal wind turbines are identified including their tendency to save economically feasible land and to reduce noise pollution that is often associated with onshore turbines. The smoothness of the water surface also makes energy collection easier because there are no obstacles as in the case of land. The use of wind as a source of energy has a high potential for growth. This can be evidenced by the high level of investment undertaken by various countries around the world. Many countries especially in Europe want to ensure self sufficiency in wind energy such so as to reduce costs incurred in the use of other forms of energy. At this rate, wind energy could be used to provide energy for the world's electricity needs. Such an achievement however will only be possible if the concept of creating a powergrid is implemented. This way, wind energy will become more reliable and hence eliminate the need to set back-up power supply.
