Offshore Wind Farms

Offshore wind farms use the power of the never-ending ocean breezes to create green, renewable, and efficient electrical energy.^[1] While found mostly off the European coasts they have begun to gain in popularity and have started to appear around the world. For example the United States have just begun multiple projects in order to to bring them into the forefront of the energy game. This might come as a surprise considering the amount of wind turbines found onshore. Unfortunately the cost of constructing offshore wind farms has deterred both government and private investment. However, as stated previously, several farms have been built in Europe and a handful have been established in Asia. Their growing popularity has been linked to the successful application as well as benefits they contribute. Some benefits include: the fact that they can not only fulfill energy goals thus reducing our need to use other costly (and environmentally detrimental) methods, they can do this while reducing greenhouse emissions which leads to a slow down of the climate change we are experiencing worldwide.^[1]

How It Works[edit | edit source]

Wind is the key factor that makes these turbines work. The location of the turbines within the ocean is an important factor as it allows for a more consistent strength of wind than could be acquired on land. This wind that passes causes the blades to rotate.^[1] Sensors within the turbine move the head of the machine to the area with the most optimum wind velocity. The blades subsequent rotations create power which is then gathered by a generator. This generator then converts the rotations into electricity. From there this electricity is transmitted back to land via subsea cables.^[2] Each unit can last up to 20 years.^[1] The amount of energy generate depends on a number of factors. This can be the speed of the wind, the size of the unit, etc.^[1] Overall these wind turbines stand roughly 246 feet above the sea level.^[2] This is said to be able to power approximately 200,000 Chinese homes.

Types of Offshore Wind Farms[edit | edit source]

Often times one of the biggest problems faced when attempting to implement an offshore wind project is how the project planner should go about mounting the wind turbines. There are different methods that will be employed depending on the depth of the sea bed below the water's surface and the geology of the sea bed.^[3]

Fixed-Foundation[edit | edit source]

Fixed-foundation offshore wind projects involve actually attaching and "fixing" the base's of the turbines to the sea floor. When attempting to "fix" the turbine there are 3 different method's used that are chosen based on sea floor depth. Regarding installations at depths below 15 meters, monopiles are used. These strictures are thick steel cylinders that are usually buried up tp 30 meters below the sea bed in order to fully anchor the tower. For turbines that need to be elevated at least 30 meters above sea level to avoid being hut by waves, the gravity anchors are used. These involve using a large concrete or steel platform with a diameter of approximately 15 meters and a weight of approximately 1,000 tons. At depths of 30 - 35 meters however, more complex foundation structures are required. Companies usually use jacket foundations. These foundations include a lattice framework that feature three or four sea bed anchoring points to ensure maximum turbine stability.^[3]

Floating[edit | edit source]

When waters exceed a depth of 60 meters it is no longer possible to fix turbines directly to the sea floor. Given the fact that much of the worlds best wind energy is located offshore in areas where turbines cannot be fixed, companies have begun to develop technology that allows for the turbines to float safely on the water's surface.^[4] In order to make this possible 3 types of floating foundations are used. The first are Tension Leg Platforms or TLP's. These structures are bottom founded floating structures which are moored at the seabed by steel tethers connected to driven piles. They are able to move like an inverted pendulum with minimal heave, pitch and roll motions to maintain a consistent distance between the sea floor and the water's surface. Typically sued for oil drilling, these structures are incredibly reliable and stable.^[5] The second floating foundation type is the spar buoy. A spar buoy is a cylindrical shaped steel or concrete ballast-stabilized structure that resembles a fixed monopile foundation. These buoy's are stable as it's center of gravity is below it's center of buoyancy. This means that the upper part of the structure is lighter than the lower part of the structure, raising the center of buoyancy. A common model set too be utilized is the Hywind Spar Buoy. The third and final platform type is the semi-submersible platform. This platform is made up of 2 separate hulls, with the upper hull providing the nessisray buoyancy for the platform while the lower hold provides the stability required to maintain the floating status. Both spar buoys and semi-submersible platforms generally use catenaries or taut lines made of wires, ropes or chains anchored to the seabed.^[6] Floating wind turbines are moored to the seabed with multiple mooring lines and anchors in much the same way that an oil platform would be moored.^[4]

Compared to the fixed foundation wind farms, floating offshore wind farms are relatively new and untested. There are only 3 floating offshore wind farms present today. The first farm was completed in 2017 in Peterhead, Scotland and is composed of five turbines capable of producing up to 30 MW of energy. Scotland also has another floating offshore wind project, the Kincardine Offshore Windfarm located in Aberdeen. This farm has been dubbed the biggest on the planet, with is being composed of turbines combining for 50 MW. The final offshore wind project, WindFloat Atlantic, is located in Portugal and is capable of producing up to 25 MW.^[7]

Where they are being used[edit | edit source]

Europe[edit | edit source]

Multiple European countries have begun to adopt the technology. The first was Denmark back in 1991.^[8] Since then offshore wind power has been developed in Belgium, Finland, Germany, Ireland, the Netherlands, Norway, Sweden, and the United Kingdom.^[1] As time goes on other European countries will continue to develop them. Currently offshore wind farms supply 11.4% of the EU's electricity.^[9] Many reasons could be argued as to why Europe has a large amount of wind power as compared to the rest of the world (the United States in particular). One of the reasons could be that even though the costs of offshore wind farms is extremely high the public still supports it.^[10]

Asia[edit | edit source]

While relatively new to the game as of 2010 China has a total of 34 turnbines.^[1] This is said to power approximately 200,000 households.^[11] This shows how quickly and how beneficial wind energy can be when utilized.

Pros and Cons[edit | edit source]

Pros[edit | edit source]

Wind turbines have numerous pros associated with them. They range from the obvious to the lesser known. First we have the increase in green, renewable, local energy. This is a plus in all rings no matter which we look at. If we have energy coming in from the wind turbines, we rely less on other forms of energy. Some of these are less than attractive on the landscape.^[1] The less of these we are forced to rely on the more our country is beautified. Aside from this, research has shown that the offshore wind farms can also serve as storm breaks helping lessen the impacts of natural disasters such as hurricanes.^[12]

Cons[edit | edit source]

The biggest con is of course the price. Compared to other forms of energy the costs are high. This is including on shore wind farms.^[13] This might be one reason that in the United States we have a large amount of on shore farms but no offshore; even though the amount of energy produced is far greater.^[1]

References[edit | edit source]