Europe is the homeland of offshore wind energy with more than 91% of the worlds installed offshore capacity. The development is boosted by national incentives and rich European funds, but on the other hand is mostly based on the benefit of having large shallow waters in the North Sea and nearby Baltic Sea, English Channel and Irish Sea, where the BOWFs are being built. The shallow waters are, however, limited in size and developers will be required to explore alternatives. Floating wind has the potential to en- able the exploitation of the vast deep sea areas in the North, Atlantic and Mediterranean Sea [68]. Figure 2.19 shows a map of the North Sea and po- tential floating wind applications. The areas with lighter color are shallow waters, which are typically close to the shore and suitable for BOWTs. The darker areas are deep waters, where floating turbines are applicable. Around the Norwegian shoreline lies a deep water channel that is suitable for ballast stabilized designs as the Spar.
TLP based designs can applied in medium water depth areas such as close to the English coast. Semi-submersible platforms can be located both from shallow to deep waters [68]. Norway was the first mover in floating wind and installed the world’s first floating wind turbine Hywind. Recently, the Ministry of Petroleum and Energy has announced plans to open an area off the coast of Rogaland for floating offshore wind applications as well as a potential site near to the border to Denmark [70]. However, the Norwegian Sea features harsh conditions with rough weather, extreme waves and large depths, which is even for floating wind a challenge. SWAY a Spar buoy prototype, for instance, was installed in 2011 off the Norwegian cost and sunk due to extreme weather conditions [28].
The United Kingdom has shown a strong interest in the development of floating wind. The Crown Estate as well as the Scottish government and UK’s Energy Technology Institute have launched major programs to fund deep offshore wind. Hywind Scotland, the world’s first floating wind farm has been commissioned in October 2017 and is located off the Aberdeenshire coast in Scotland. Several more floating wind projects are scheduled for construction of the Scottish coast by 2020 [28, 62].
The Mediterranean Sea and the Atlantic Ocean in contrast to the North Sea possess large deep water areas, but the majority is unsuitable for offshore wind applications, even for floating find. The reason is that most areas are too deep and the installation of mooring lines and anchors would not be feasible in terms of cost and technology-wise. However, suitable locations for floating wind can be found in the French waters, around the Spanish and Portuguese cost, as well as in Italian and Greek waters. Figure 2.20 demonstrates the suitable locations.
France is an active player in floating wind. In early 2019, the European Commission has agreed to support four French floating wind demonstration projects, each consisting of either three or four turbines with a total capacity of 24MW. One project will be located in the Atlantic Ocean, while the other three projects will be located in the Mediterranean Sea. France aims to con- sume 40% of renewable electricity by 2030 and floating wind has the potential to make its contribution. In particular, the recently released Multiannual Energy Programme has proposed the tendering of around 6GW of fixed and floating offshore wind by 2028 [71]. Prominent demonstration projects that have been realized are WinFlo, Vertiwind and FLOATGEN [28].
Portugal possesses a large exclusive economic zone and has high potential for floating wind with deep waters. The government has recognized the po- tential and installed WindFloat Europe’s second large scale floating system after Hywind. The government plans to extend the project to 27MW in a second phase and up to 150MW in a third phase [28].
Spain has also potential for floating wind and several key players in the floating wind market are of Spanish origin. For instance, promising FOWT concepts that have been developed by Spanish companies are Iberdrola’s TLP, the semi-submersible platform by Nautilus, the Windcrete Spar-buoy concept by researchers of UPC-BarcelonaTech or the SATH concept by Saitec Offshore Technologies. Besides that, Spain possesses suitable loca- tions for floating offshore wind employment with deep water sites close to load centers and good wind resources. Only recently, a prototype of a twin- rotored FOWT developed by EnerOcean has been installed off the Canary Islands and the Norwegian developer Equinor has secured a permit to build a 200MW FOWF also close to the Canary Islands [72]. Besides the men- tioned countries, prototypes are also being developed in Germany, Sweden and the Netherlands [28].
Japan has a large interest in floating offshore wind development for sev- eral reasons. First, the nuclear catastrophe of Fukushima has demonstrated the high risk of nuclear power and the Japanese people are demanding a diversification of the energy mix. Second, the country lacks of suitable sites for onshore wind, since the country is characterized by mountainous ter- rains and densely populated regions. Lastly, the Japanese coastline falls rapidly off, which causes deep waters near to the coast [11]. The follow- ing map shows potential locations for the deployment of FOWTs. Several demonstration projects have been realized in Japan, including conventional floating wind concepts, but also multiple-turbine substructures such as the WindLens project and hybrid systems such as SKWID.
Figure 2.21: Suitable sites in Japan [73].
The most prominent project is Fukushima FORWARD, which is led by a large consortium including Mitsubishi, University of Tokyo, Mitsui, and Marubeni among others. The project includes the construction of two types of semi-submersible floating structures, one spar design and the world’s first floating substation. In 2013 one semi-submersible floating turbine with a capacity of 2MW and the floating substation was installed, followed by the installation of the 7MW semi-submersible floating substations in 2015. The advanced spar design with a 5MW turbine has been commissioned in 2016. After, the successful operation of the prototype, the floating offshore wind farm will like be extended to 100MW in phase 3 and possibly 1,000MW in phase 4 [11].
The United States is one of the countries with most onshore capacity installed. However, it has also a large potential for offshore wind at its east and west coast and in particular for floating wind since more than half of the offshore wind resources are estimated to be located in deeper waters.
Furthermore, the most populated parts of the country are located at the coast, which additionally favors the use of offshore wind. So far only one offshore wind farm has been installed located off Rhode Island consisting of BOWTs. However, several more are projected including floating offshore wind. The state of Maine and California have shown in particular interest. A first 20kW FOWT prototype, the VolturnUS, was installed and tested by the consortium DeepCWind for a few months outside of the Castine harbor in 2013 [28].
Other markets that may get popular in the near future are China, Taiwan and South Korea. China the leader in onshore wind energy has so far only two BOWFs installed. More projects are expected in the upcoming years and investigations have been started floating wind as well. However, in con- trast to Japan, China does have large shallow waters and they are located near the consumption centers at the cost. Thus, the future will tell who will win the race, bottom-fixed wind, floating wind or a mix of both. Taiwan and South Korea have also shown their interest in floating offshore wind. The French floating substructure designer IDEOL yet has firmed an agree- ment for collaboration in Taiwan and the German company GICON has been in contact with delegates from South Korea to evaluate the potential application of their floating substructure design [68, 74, 75].