Offshore wind farms are electrical powerhouses built in bodies of water. These farms can be erected in lakes, coastal waterways, and oceans. The cost of building one increases the further the wind turbines are located from the coast. This increase in expense is based upon the distance electricity needs to travel back to land, and cost of constructing the base on which wind turbines will be located.
As of 2009, the Horns Rev 2 wind farm in Denmark is the largest offshore farm in the world. It is located on Horns Reef, which is a shallow area of the North Sea. The combined energy output of the two offshore wind farms located at Horns Rev 2 is about 369 megawatts (MW) per year. This is enough energy to power 350,000 homes in Denmark. The United Kingdom generates the most wind turbine power, with Denmark falling into second place.
Currently, offshore wind farms are built primarily in shallow waters. Deeper waters are often characterized by high wave heights, which make for additional construction costs. Models are being developed to decrease the cost of placing offshore these energy stations further offshore, where wind speed and consistency could increase output. These models include floating offshore wind farms.
As of January 2009, there were 28 offshore wind farms currently supplying electrical energy to eight countries. Seventeen more offshore wind farms were under construction, with scheduled completion dates ranging from 2009 to 2012. In addition, there are 35 proposed wind farms to be built in the United States, Germany, and China. The United Kingdom is responsible for 15 of the wind farms currently under construction, or in the proposal stages.
While Denmark’s Horns Rev 2 wind farm is the largest at an output of 369 MW, a proposed wind farm in the Great Lakes area between the United States and Canada would supply more than 10 times that amount. Early estimates mark potential electrical output for the Wasatch Wind Farm, a combination effort between the two countries, at 4400 MW. The company set to build the Wasatch Wind Farm, Trillium Power Wind Corporation, is currently working on the three projects — the Superior Array, Great Lakes Array, and Trillium Power Wind 2 offshore wind farms — among others.
Offshore wind farms take approximately six months to construct and may last up to 20 years before being decommissioned. Time spent in the building and decommission stages may pose a threat to surrounding marine life. Marine conservation groups and wind energy companies are researching these effects, and any potential changes that could decrease the environmental impact on marine life.