The world’s first floating offshore wind farm, Hywind Scotland pilot park, developed by Norwegian energy company Equinor (previously known as Statoil), became operational in October 2017. The five-turbine, 30-MW wind farm can power 20,000 households and is approximately 30 km (18 miles) off the Aberdeenshire coast. While bottom-fixed offshore wind farms have been seen to have a 45-60% capacity factor in the winter season, Hywind Scotland operated at 65% of its maximum theoretical capacity in winter months. When compared to other solar and wind energy facilities, which have an approximate 30-40% capacity factor, the difference is significant.
Why offshore? Why floating wind farms?
The main advantage of offshore wind farms is that offshore wind speeds are generally stronger and more consistent than on land. Small increases in wind speed can result in large increases in energy production: A turbine in a 24 km/h (15 mph) wind can generate twice the amount of energy as one in a 19 km/h (12 mph) wind.
Another advantage is that, when compared to land-based wind turbines, offshore turbines do not need to be specially designed according to the terrain, making mass production of turbines possible, which lowers costs. Currently, the largest wind turbine in the world has a capacity of 9.5 MW, but larger 12-MW turbines are being designed. Offshore bottom-fixed wind farms are typically built in shallow depths (up to 60 m, or about 200 ft); however, 80% of the global offshore wind power potential is in areas where the sea depth is greater than 60 m, making floating wind farms necessary.
Disadvantages and points of consideration:
The disadvantages of building offshore include possible turbine damage from severe storms along with the high costs and challenges of building reliable wind farms in deep water. Besides the expense of developing floating turbine technology, the mounting and installation of these massive steel structures is costly (installation of the five Hywind turbines cost approximately $263 million USD), and they must be able to endure harsh conditions. The Hywind turbines are 254 m (833 ft) tall, 176 m (577 ft) of which is above the water surface and 78 m (256 ft) is submerged.
Another issue with floating wind turbines is the difficulty and cost of access and maintenance. Environmental concerns must also be considered, as turbine blades create a potential hazard for birds, meaning that wind farms cannot be placed on bird migration routes.
Worldwide trend and outlook:
The current worldwide offshore wind energy capacity is 19 GW, with 84% of this found off the shores of European countries. The global offshore capacity is expected to reach 115 GW by 2030, with the offshore wind power industry showing rapid growth in North America, East Asia, and India. Wind power is one of the largest sources of renewable energy in the United States, producing 6.6% of all electricity, with the majority of this production occurring on land. The first offshore wind farm in the United States, the 30-MW capacity Block Island Wind Farm off Rhode Island, became operational in 2016. The coasts of Hawaii, New England, and California have been identified as promising areas of investment for floating wind farm technology in the United States.
The cost of energy from floating wind farms is expected to be US $0.05-0.07/kWh by 2030 and will continue to drop with improving efficiency and technology. The general inclination is in favor of offshore wind farms, and increased growth is expected in the United States and worldwide. In late 2017, the US DOE announced $20.5 million funding to conduct research and development in offshore wind power, resulting in a $41-million consortium in June 2018 with the New York State Energy Research and Development Authority as administrator of the consortium. The total global offshore wind market is expected to exceed $60 billion USD by 2024, with China emerging as one of the potential leaders in this rapidly developing market.
During the past 5 years, another renewable energy technology — floating solar arrays — has been showing great potential and growth. PreScouter covered this technology in another article for Solar Power World. Have a read here!
