FLOATING WIND TURBINES BUOY HOPES OF EXPANDING RENEWABLE ENERGY
Off the east coast of Scotland, in water more than 300 feet deep, five towering turbines weighing thousands of tons float in the North Sea. Installed in 2017, the turbines power about 36,000 homes a year.
Wind farms have been erected on land and at sea for decades, but Hywind Scotland, operated by Norwegian oil giant Equinor AS A, is the first to float. Instead of being inserted into steel tubes buried in the seabed, the turbines sit in cylindrical buoys that are fixed to the seabed by mooring lines. The approach promises to enable wind farms in much deeper water, where there are often stronger winds, opening up swaths of untapped coastline to renewable energy.
Equinor believes that there are many countries where floating wind could be the best option for generating renewable power. In some places, such as Japan, South Korea and the U.S., a steep drop off the continental shelf means the water is too deep for fixed wind turbines, which are limited to depths of around 60 meters, or just under 200 feet.
The technology is gaining interest as governments scramble to reduce their carbon emissions footprint. The 2015 Paris climate accord, where governments agreed to limit global temperature increases to less than 2 degrees Celsius, with an ambition to cap them at 1.5 degrees Celsius, has focused attention on limiting emissions, which renewable energy helps address.
Still, floating wind is almost double the cost of fixed offshore wind, which needs an average price of $84 per megawatt-hour of electricity for projects to break even, according to industry group the Global Wind Energy Council. There are dozens of concepts for floating platforms in the works, preventing the savings that come with standardization and mass production. Longer cables needed to send power back to land can also increase expenses. The internal rate of return, a measure of profitability of investments, is around 10% for fixed wind and not yet known for floating wind.
Another limitation is the slow pace at which governments are developing policy to enable projects.
“We will start with where you see an appetite from government and where you see an energy need that cannot be met by obvious, much cheaper options like onshore wind, solar and to some degree fixed offshore wind,” says Sebastian Bringsværd, head of floating wind development at Equinor.
Some governments are realizing that floating wind may be their only option for meeting carbon reduction targets, particularly if they have limited space for solar and wind projects onshore, Mr. Bringsværd says. Whether fixed or floating, wind farms in the sea don’t face as much public resistance over their impact on the environment and landscape. They are not visible from shore when they are farther than 30 miles out. Cables can be buried all the way to the power station, but this can be more difficult if the cable lands ashore in a residential area.