Pressures for land use and concerted campaigns to prevent the construction of wind farms is forcing wind farm developers in western Europe to consider building wind farms offshore. Offshore wind farming has some significant advantages. The wind regime is both more predictable and more reliable. Turbulence is lower, so wind turbines should last longer and wind farms can be sited far enough offshore to make them virtually invisible. Offshore sites also offer the possibility of building wind farms with capacities of 1000 MW or more.
Against this, the primary barrier is cost. Building a wind farm offshore costs between 40% and 100% more than building a similar farm onshore. Maintenance costs are higher too. However the higher wind speeds available offshore mean that output will generally be higher offshore.
The main additional cost is for construction of the wind turbine foundation. This can cost up to 25% of the total installation cost offshore. Onshore it is likely to be 16% or less. Grid connection is also more expensive. As a result, while the turbine itself may account for 64% of the cost of an onshore installation, it can be 45% less of the total offshore cost.
This high foundation cost favours large wind turbines for offshore projects. In 2004, the typical offshore wind turbine was between 2 and 4 MW in capacity and larger offshore turbines were in development.
A variety of methods have been used to build offshore foundations. The most popular is a monopile, a single pillar support which is constructed using either pile driving or drilling. Tripods have also been used and experimental work is examining the plausibility of using a floating wind turbine support.
Conditions offshore are generally more severe than onshore and offshore turbines must be 'marinised' to protect them from the environment. This adds around 10% to the cost of the offshore wind turbine compared to onshore. Marinisation techniques from the offshore oil and gas industry have been exploited to protect offshore turbines. The experience from this industry is also proving valuable when installing offshore wind turbines.
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Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.