Horns Rev 1 was the first large scale offshore wind farm in the world, at 160 MW, four times as large as the previous largest, the Middelgrunden at 40MW. Built by Danish Energy company Elsam, it was the first offshore wind farm in the North Sea. It was the first offshore wind farm to use the monopile foundation type and to have the transformer placed on a platform by the wind farm in stead of on the shore. The construction of Horns Rev 1 was a very important step for the establishment of the offshore wind industry, as it was the first to make use of a lot of technologies, that has since become industry standards for offshore wind. The farm has a total of 80 Vestas V80-2.0 MW units were installed by the Danish offshore wind farms services provider A2SEA in 2002 with the last turbine coming into operation on 11 December 2002. It receives a guaranteed price of 0.453 DKK/kWh for the first 42,000 hours, paid by electricity consumers. In 2005 60% of the wind farm was sold to Vattenfall which also is operator for the park. The price was DKK2bn. A radar has shown details of the wind patterns, improving local short-term forecasting. Turbines are laid out as an oblique rectangle of 5 km x 3.8 km. The distance between turbines is 560 m in both directions. The main method of transport to the first wind park is an adapted Eurocopter EC-135 helicopter when winds are less than 19 m/s. Hoisting the workers to and from a small platform on each turbine allows access to the park regardless of sea conditions which would otherwise prevent sailing in the area for a large part of the year. Vattenfall can change a gearbox in a day, and the farm has an availability of 96-97%. Two turbines are burnt out, and are uneconomic to replace with less than 10 years left. Grout between monopile and tower was damaged by vibrations, requiring a costly fix.
Horns Rev 2
In May 2008, Dong Energy began construction of the second wind farm in the Horns Rev area, Horns Rev 2. Construction was completed in September 2009 and was inaugurated on September 17, 2009 by Prince Frederik on the Poseidon accommodation platform. When inaugurated, Horns Rev 2 was the largest offshore wind farm in the world until Thanet Wind Farm opened on 23 September 2010. For the year of 2012, HR2 reached a capacity factor of 52.0%. It receives 51.8 øre/kWh for the first 50,000 hours, paid by electricity consumers. The farm has had some cable outages, and blades are being renovated. The Horns Rev 2 consists of 91 Siemens Wind Power SWT 2.3-93 wind turbines with a total generating capacity of 209 MW. The foundations are monopiles like on Horns Rev 1. It has the first offshore wind farm accommodation platform in the world, named Poseidon. It is connected by walkway to the transformer platform, and is large with 3 decks and weighs 422 tons. On-site accommodation is cheaper and more efficient than transporting service personnel by boat 2 hours from Esbjerg harbour away. A turbine is visited 10 times a year on average, mostly for routine service, and 1-2 times for fixing faults. Flying people by helicopter to turbines like on Horns Rev 1 is not possible on Horns Rev 2 as the turbines there are not built for it, although the transformer platform has a helipad. Poseidon has 24 rooms of 12 square meters each fitted with TV and internet. There is a gym, kitchen, dining room, laundry room, and a study room. Inspired by Poseidon, a similar platform is being built at the DanTysk wind farm.
Horns Rev 3
In April 2012, most of the Danish Folketing agreed to send out tenders in 2013 for a 400 MW wind farm at Horns Rev called Horns Rev 3, and a 600 MW at Kriegers Flak in the Baltic Sea, both likely receiving 90 øre/kWh for the first 50,000 hours. This is expected to raise wind power in Denmark above the 39% of annual electricity production, which includes the 400 MW Anholt Offshore Wind Farm. The Danish Energy Agency expects construction candidates for Horns Rev 3 to have experience with installing and operating a large offshore wind farm. Some of the area is an old minefield from World War Two. Four bidders were qualified for the tender. Vattenfall won the tender in February 2015, at a price of 77 øre/kWh, well below the 105 øre at Anholt. Vattenfall states that they bid unaggressively against strong competition without sacrificing margins. The price reduction contributes to a smaller "green subsidy" over the next years. Horns Rev 3 consists of a total of 49 MHI Vestas V164-8.3 MW units, capable of producing 406.7 MW. Three transformers were installed in July 2016. The first turbines started to produce electricity for the grid in December 2018, and the last turbine was installed in January 2019. The official inauguration of Horns Rev 3 was on 22 August 2019.
