The 2 major types of offshore foundations are fixed-bottom & floating. Fixed-bottom make up the largest share of offshore wind however as water depths increase, fixed-bottom becomes less feasible. A key factor being an increase in cost and complexity in the construction.
The opportunity for floating offshore wind (FOW) is in these greater water depths (>60m). FOW can also take advantage of the stronger and more consistent wind speeds, usually found in locations at these water depths. As of 2022 it is estimated there is over 200MW of floating wind power installed and online.
Recent increases in energy costs combined with environmental concerns have furthered the interest in commercial wind power.
Wind power has a long history dating back thousands of years. However, the modern era of wind power began in the late 19th century with the invention of wind turbines. In 1887, Professor James Blyth built and installed a wind turbine to supply electricity to his cottage in Scotland. This was the earliest documented example of a wind turbine used for generating electricity.
Over 100 years later, in 1991, one of the first offshore wind farms, Vindeby, was commissioned off the coast of Denmark. Consisting of 11 wind turbines the farm produced a total capacity of 4.95MW. The water depths at Vindeby farm site were less than 10m, therefore the project utilised fixed-bottom foundations.
As offshore wind technology advanced, farms have been constructed in deeper waters. However, as was found in the oil and gas industry as water depths increase, traditional fixed-bottom foundations become less feasible. A key factor being an increase in cost and complexity in the construction of the foundations.
There will continue to be a demand for fixed-bottom wind farms as the worldwide capacity for offshore wind power increases. However, floating offshore wind farms provide a solution for water depths where fixed-bottom turbines cannot be deployed. Therefore floating wind will compliment fixed-bottom in the global offshore wind industry.
Floating turbines can also take advantage of the stronger and more consistent wind speeds. Usually found in locations at these water depths.
Hywind is considered the first, large-capacity floating offshore wind project. It was deployed off the coast of Norway in 2009 in water depths of 220m. The demonstration project consisted of a 2.3MW turbine, mounted to a floating spar buoy. This was then moored to the seabed using a steel chain catenary configuration.
The success of the Hywind demo, combined with other prototypes led to the development of the first floating offshore wind farm. Hywind Scotland was deployed in 2017 in water depths between 95-120m. Considered the first floating wind farm, it consists of 5x 6MW turbines, providing a total capacity of 30MW. This generates enough renewable energy to power approximately 20,000 homes.
As of 2021 the total worldwide capacity of offshore wind power was 57.2 GW. The majority of this will be fixed-bottom turbines however the proportion of floating offshore wind is set to increase.
The offshore oil and gas industry provides many insights for permanent mooring solutions. However, for floating offshore wind farms there will be some new and unique challenges to solve.
Mooring multiple floating assets in shallow waters, compared to a single asset in deep water. The impact of the mooring footprint and how to achieve restoring forces with shorter mooring lines. Potential to enable seabed contact for synthetic fibre ropes or mitigate against it completely. Address some existing challenges with regard to synthetic fibre ropes such as marine fouling and cutting damage.
Bekaert are dedicated to addressing these market challenges. Utilising our experience and expertise in material science and coating technologies. To date Bekaert have worked in various joint industry projects (JIP) dedicated to floating offshore wind. As well as supplying mooring solutions to many projects around the world.