Offshore wind power development in Europe and its comparison with onshore counterpart
Introduction
Wind is air in motion. Since the earth's surface is made of various land and water formations, it absorbs the sun's radiation unevenly. Wind is produced by the uneven heating of the earth's surface by the sun [1]. A wind energy system transforms the kinetic energy of the wind into mechanical or electrical energy that can be harnessed for practical use. Mechanical energy is most commonly used for pumping water. Furthermore, it can also be used for many other purposes such as grinding grain, sawing, pushing a sailboat, etc. Wind electric turbines generate electricity for homes and businesses and for sale to utilities [2]. Wind energy can be deployed rapidly, as turbines and wind plants are quick to install. It is the cheapest way of renewable energy, which encourages investment. It also creates benefits in terms of employment, investment, research, economic activity and energy independence in the electricity sector [3].
Furthermore, it is well known that wind energy is one of the cleanest and most environmentally friendly energy sources, and unlike fossil fuels, the wind will never be depleted. All forms of energy production have an environmental impact, but the impacts of wind energy are low, local, and manageable. These environmental impacts are negligible when compared with conventional energy sources. The significance of wind energy originates from its friendly behavior to the environment. Due to its clean, wind power is sought wherever possible for conversion to electricity with the hope that air pollution from fossil fuels will be reduced [4].
There are different alternatives for wind energy such as onshore and offshore. Onshore, wind energy has been utilized for power generation for more than two thousand years. On the other hand, the history of offshore wind power generation is fairly recent. In recent years, the wind power sector has begun to move offshore, i.e. to use space and good wind speeds on the open sea for large scale electricity generation [5]. Offshore wind farms are constructed in general on the continental shelf area which is about 10 km away from the coast and 10 m deep. Compared with land, offshore wind turbines must be fixed on the seabed, which demand a more solid supporting structure. Submarine cables are needed for transmission of electricity, and special vessels and equipments are required for building and maintenance work. These factors create high costs, with double or triple the cost on land [6].
Offshore wind turbines are less obtrusive than turbines on land, as their apparent size and noise can be mitigated by distance. Because water has less surface roughness than land (especially deeper water), the average wind speed is usually considerably higher over open water. Capacity factors are considerably higher than for onshore and nearshore locations which allow offshore turbines to use shorter towers, making them less visible. In addition, installing wind turbines offshore has several advantages over onshore development. Onshore, difficulties in transporting large components and opposition due to various siting issues, such as visual and noise impacts, can limit the number of acceptable locations for wind farms. Offshore locations can take advantage of the high capacity of marine shipping and handling equipment, which far exceeds the lifting requirements for multi-megawatt wind turbines. On land, larger wind farms tend to be in somewhat remote areas, so electricity must be transmitted over long power lines to cities. Offshore wind farms can be closer to coastal cities and require relatively shorter transmission lines, yet they are far enough away to reduce visual and noise impacts [7].
Offshore wind farms make new technological demands on the wind power industry not only with respect to the development of the wind turbines themselves and with their connection to the electricity grid but also with respect to the logistics of transport, installation, operation and maintenance. This has led to the need for a new combination of research areas [8]. In this study, history, current status, technical potential area, investment cost, employment, industry and installation of offshore wind energy in Europe are investigated in detail, and also compared to its onshore counterpart.
Section snippets
Advantages and disadvantages
There are many advantages of offshore wind energy, compared to its onshore counterpart. Offshore wind power is more complex and costly to install and maintain but also has several key advantages. Winds are typically stronger and more stable at sea, resulting in significantly higher production per unit installed. Wind turbines can also be bigger than on land because it is easier to transport very large turbine components by sea. Installing wind turbines sufficiently far from the shore can nearly
Onshore
The wind has played a long and important role in the history of human civilization. Since earliest recorded history, wind power has been used to move ships, grind grain and pump water. There is evidence that wind energy was used to propel boats along the Nile River as early as 5000 B.C. The western world discovered wind power much later. The earliest written references to working wind machines date from the 12th century. These were used for milling grain. Windmill performance was continuously
Global wind power
Wind energy is the world's fastest-growing energy. Both in Europe and worldwide, wind power is being developed rapidly. In 2008, more wind power capacity was installed in the EU-27 than any other electricity generating technology, as seen from Fig. 2. A total of 8484 MW wind power capacity was installed in the EU-27. This puts wind energy ahead of any other power technology for the first time. 36% of all new electricity producing capacity installed in the EU was wind energy followed by natural
Onshore
Table 5 [23] shows the typical cost structure for a 2 MW turbine erected in Europe. The average turbine installed in Europe has a total investment cost of around €1.23 million/MW. The turbine's share of the total cost is, on average, around 76%, while grid connection accounts for around 9% and foundation for around 7%. The cost of acquiring a turbine site (on land) varies significantly between projects. Other cost components, such as control systems and land, account for only a minor share of
Employment
It is impossible to manufacture, build, install and maintain wind turbines without people. It is equally impossible to plan, gain permits for and supervise a wind farm without them. Unsurprisingly then, employment related to wind energy has also gone up strikingly in recent years. Over the past 5 years, the EU wind energy industry has created more than 60,000 new jobs. On average, the wind energy sector in Europe has employed 33 new people every day, 7 days a week over the past 5 years [27].
Industry and installation
A wind power system is a sophisticated combination of components and sub-systems that have to be designed in an interdisciplinary and integrated manner. In addition, the size and complexity of wind turbines is increasing rapidly over time, as seen in Fig. 9 [27]. Wind energy technology itself also moved very fast towards new dimensions. At the end of 1982, a 55 kW wind turbine with a 15 m rotor diameter was state-of-the-art. Today, 5000 kW turbines with a rotor diameter of around 126 m are
Conclusions
Europe is an energy intensive continent, which relies heavily on imported fuels, and it is faced with the global challenges of climate change, depleting indigenous energy resources, increasing fuel costs and the threat of supply disruptions. For this reason, Europe must use the opportunity created by the large turnover in capacity to construct a new, modern power system capable of meeting the energy. In recent years, wind energy has become a valuable and dependable source of electricity
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