How can a top-heavy structure that is twice as high as the Oslo Plaza Hotel float steadily through high waves and in strong winds?

There is a lot of talk about floating wind power just now. Simply put, this concept involves mounting traditional fixed wind turbines on floating structures that we know from the oil and gas industry. However, there are some differences that require extra consideration.

"When it comes to floating wind power, we face some difficulties that we've not experienced before in the oil, gas or wind industries," says Emilie Schjøtt Brackman, a senior consultant with DNV.

Brackman has been highly involved in onshore and offshore wind power in the past few years.

"When a top-heavy structure that is as tall as two Oslo Plaza Hotels is to float in the middle of the ocean, we obviously face a few challenges. The fact that the structures are preferably to be located in areas where there is as much wind as possible, and thus often high waves, does not make the situation any easier," she says.

In addition, floating wind power costs are higher than the costs of traditional fixed offshore wind power. According to Magnus Ebbesen, DNV's Business Lead Floating Wind Advisory, the current cost level is primarily linked to the size of the facilities.

"A fixed wind farm usually has a capacity in excess of 800 megawatts, while the biggest floating wind farm, which is to be built soon, has a capacity of 88 megawatts. In addition, the structure on which the wind turbine stands is more expensive to make and a number of risk factors push the prices upwards," he says.

However, according to Ebbesen the costs will fall dramatically in the future.

"Once we build larger farms and gain more experience and the fabrication work is industrialized, this will also be far cheaper. Fixed wind farms were also viewed as far too expensive and risky at one time. That changed quickly," he says.

Driven forward by a Norwegian centre of excellence

DNV's head office is at Høvikodden, outside Oslo. Here, they have developed their own "centre of excellence" for floating wind power and use it to support the global market for floating wind power.

"How do you work on floating wind power?"

"We provide a number of services from our centre at Høvik. We primarily ensure that the structures are equipped for the future. They must be able to stand for at least 25 years and cope with all kinds of wind and weather," says Ebbesen.

In order to safeguard these enormous structures, DNV develops standards for the industry as a whole. This is done by combining the expertise the company has accrued over 150 years with proposals from leading industrial players.

DNV's floating wind power standard was one of the first when it was launched in 2013. It has been used for a number of floating wind projects, including the world's first floating wind farm, Hywind Scotland.

"We believe floating wind power will be an important energy source in the years to come, and we therefore focus on our standards helping to keep costs down so that floating wind power can make a good contribution to the energy transformation we're now facing," says Ebbesen.

Fortunately, floating wind power does not need to be as cheap as other energy sources, quite simply because the floating structures themselves have so many other benefits.

"The main argument in favour of floating wind power must be that the platforms can be placed 'anywhere' in the ocean. The good coastal areas that are suitable for fixed platforms are gradually being used up, but floating wind farms can be located in windy places far from the nearest civilization. This means that floating wind power's capacity is in the long term far greater than that of fixed wind power," he says.