Floating turbines that can operate far out at sea could help the renewables sector make better use of offshore wind. Helen Knight reports.

From the surface, the spinning blades of the wind turbine sitting off the coast of Norway look much like those of any other offshore device.
But it is underneath the waves where the difference becomes clear.
That is because unlike conventional offshore wind turbines, the Hywind device is not fixed to the seabed by foundations, but is instead attached to a cylindrical structure that floats in the water. Tethers anchored to the ocean floor prevent it from drifting out to sea.
Now the company behind the floating turbine, Statoil, is planning to build five 6MW devices off the coast of Scotland.
Floating devices can tap into the vast energy resources available further offshore, where wind speeds tend to be higher and steadier
The 30MW pilot wind farm, which is due to be completed in 2017 near Buchan Deep, around 25km off the coast of Peterhead in Aberdeenshire, will be the first array of its kind. It is expected to generate around 135GWh of energy per year, or enough electricity to power 20,000 homes.
Unlike fixed offshore wind turbines, floating devices can be placed in deeper waters of up to 150m. This allows them to tap into the vast energy resources available further offshore, where wind speeds tend to be higher and steadier. Turbulence is also lower further offshore, which should ensure the turbines have a longer operating life.
In Europe, over half of the North Sea is considered suitable for floating wind farms, with water depths of between 50m and 220m. The European Wind Energy Association estimates that energy from turbines at depths of over 50m in the North Sea could meet the EU’s electricity needs four times over. As a result, the technology is generating increasing interest around the world, with projects already under construction or in the pipeline around the coast of Europe, Japan and the US.

In the UK, these projects are around the coast of Scotland, including the Buchan Deep site and a further two pilot farms planned near Kincardine and Dounreay.
The UK is already an acknowledged world leader in offshore wind power, with over 5GW of installed capacity. The Energy Technologies Institute, a public-private partnership between the UK government and energy companies, estimates that this could increase to between 20–55GW by 2050.
But at these levels, the number of attractive sites for fixed-bed wind turbines, less than 30km from the shore and where water depths are no greater than 40m, are likely to be few and far between. Building fixed offshore turbines in sites that are further from the shore, or in deeper waters, adds considerably to the cost and complexity of any project.
Conditions on the ocean floor can also add to the difficulties, and cost, of building fixed offshore turbines, according to Rhodri James, manager for policy and innovation at the Carbon Trust, which published a detailed report on floating wind in 2015.

“A number of fixed projects have found themselves facing quite complex seabeds, particularly where the soil is harder, so there are opportunities to locate floating wind where you wouldn’t be able to locate a fixed wind farm,” said James.
What’s more, installing floating wind turbines offshore is cheaper and simpler than fixed devices. That is because expensive heavy-lift vessels are needed to assemble and install fixed turbines on the seabed.
In contrast, most floating wind devices can be fully assembled at port-side, and then simply towed to their offshore location using lower-cost and readily available tug vessels, said James.
This is likely to make a considerable difference as the industry moves from 4–6MW turbines to 8–10MW and above, he said. “The ability to assemble the devices at port-side and tow them to site should work in the favour of floating wind over the next 10–15 years or so, as turbine sizes increase.”
Hywind structures can be used with any type of wind turbine
As a result, floating offshore wind farms should start to become increasingly attractive, said James.
This is particularly the case in Scotland, where there are high offshore wind speeds and a large number of sites at which waters become deep relatively close to the shore.
At Buchan Deep, Statoil plans to locate its Hywind devices in water depths of around 95–120m. Each device will consist of a turbine placed on top of a ballasted steel cylinder, known as a spar-buoy.
The structures will be anchored to the seabed using three mooring lines, while a pitch motion controller will prevent them moving around too much in the wind and waves.
According to Statoil, the Hywind structures can be used with any type of wind turbine, providing the combined weight of the nacelle and rotor do not fall outside the levels required to maintain stability.
A pilot Hywind device, installed off the coast of Norway and equipped with a 2.3MW Siemens turbine, has operated successfully since 2009, making it the world’s first full-scale floating wind turbine, according to Elin Isaksen, spokesperson for Statoil. In that time, it has generated around 32.5 GWh of electricity.
“The experience from the Hywind Demo has been used to further optimise the floater motion controller, so that the movement can be even better controlled,” she said. “This will become increasingly important as the turbine size increases.”
The company hopes the plant will open up new possibilities for floating wind around the globe, including the US and Japan. “We believe industrialisation of floating wind is a key opportunity for companies such as ours with skill-sets from the oil and gas business,” she said.
The Hywind plant will also pilot the use of batteries to store excess energy produced by the floating turbines for use at periods of high demand. A 1MWh lithium battery-based storage system, known as Batwind, will be installed at the site in late 2018, under an agreement between Statoil, the Scottish government, the Offshore Renewable Energy Catapult and Scottish Enterprise.
But while the Hywind plant will mark the first time multiple turbines have been installed together as an array, it is by no means the only project designed to take advantage of the winds in deeper waters.
In Japan, a project known as Fukushima Forward has been installing floating turbines at its site 20km off the coast of north-east mainland Japan since 2013.
The Fukushima nuclear disaster in 2011 stimulated Japanese interest in alternative, renewable technologies, and in particular focused efforts into offshore wind power. Unlike the UK though, Japan is surrounded by deep water, making it unsuitable for fixed-bed offshore wind, but a prime candidate for floating turbines.

In 2013, the Fukushima Forward project installed one 2MW Hitachi turbine and a floating substation at the site, which was followed in 2015 by a 7MW device, built by Mitsubishi Heavy Industries. In July this year the team installed a final 5MW Hitachi turbine, dubbed the Fukushima Hamakaze, making it the largest floating wind farm in the world, at 14MW.
Unlike the Hywind devices, the 2MW and 7MW Fukushima turbines are both installed on semi-submersibles, or buoyancy-stabilised platforms that float, semi-submerged, on the surface of the water. Mooring lines anchor the platforms to the seabed.
The four-column semi-submersible platform used to support the 2MW Fukushima Mirai turbine, which was built by Mitsui, has already survived an earthquake, measuring 7.1 on the Richter scale, and minor tsunami, as well as two typhoons.
The 7MW Fukushima Shimpuu turbine, meanwhile, is installed on a v-shaped semi-submersible, with three columns, including one supporting the turbine.
In contrast, the floating substation and Hamakaze turbine are installed on an advanced spar design, built by Japan Marine United. This consists of a shorter cylinder than conventional spar-buoy structures like Hywind, for use in shallower waters. Fins fitted around the bottom of the spar help minimise sway in the water.
But despite the apparent success of Fukushima Forward so far, the project has been expensive, according to James. And while Japan has built up a great deal of knowledge about floating wind in the process of this work, the country lacks the advantage of the offshore know-how and infrastructure built up in Europe through the fixed wind and oil and gas industries, he said.
“However, it will be interesting to see what they do beyond this stage of the project,” said James. “There has been talk of building the same site out, originally to 1GW, although it may well be closer to 100MW, in time for the Tokyo Games in 2020.”

Meanwhile, a 2MW prototype floating turbine, known as WindFloat, is also generating energy off the coast of Aguçadoura in Portugal. The device, which was developed by US-based Principle Power, has already provided more than 16GWh of electricity to the local grid, since its installation in 2011.
The company is now planning to build a three 8.3MW turbine array at the site. Like the prototype, the WindFloat turbines will sit on a semi-submersible hub consisting of three columns.
Principle Power also has plans for a further plant off the coast of Scotland, as well as arrays in Hawaii and Oregon in the US.
This summer, French offshore wind power firm Eolfi won a bid to build a floating wind farm consisting of four 6MW General Electric turbines off Groix Island, on the coast of Brittany. The turbines will sit atop four-columned semi-submersible floaters built by French naval manufacturer DCNS, in collaboration with construction company Vinci.
The wind farm, which will be anchored around 14km from the coast and connected to the shore by underwater cables, has a 20-year power purchase agreement in place.
Each 8m-wide star-shaped floater is built from concrete and steel, and ballasted with 7,000 tonnes of seawater, according to Marc Lanne, maritime senior project manager at Eolfi.
“We hope to have the devices installed at sea in 2020, which is quite an aggressive target,” he said.
France has woken up relatively late to the opportunities, said Lanne. As such, the country missed the boat in benefitting from first-mover advantage in fixed-bed offshore wind, but now recognises the opportunities offered by floating wind, he said.
“With floating wind, it’s more flexible, it’s further from the coast, which means it is less obtrusive, and manufacturing is easier because everything can be constructed in the harbour,” said Lanne.
Once the pilot wind farm is in operation, Eolfi hopes to be able to move quickly to build a commercial plant in a few years. And although the company is currently reliant on French government grants, it hopes to be able to compete with market prices for offshore wind in 10–15 years.
If the technology is given the support it needs, the Hywind plant could be the first of many wind farms floating off our shores.
Likewise, Statoil estimates that it can ultimately reach a levelised cost of electricity (LCOE) from its floating wind farms of £85–95/MWh.
So far, the data from technology developers suggests that this figure should be achievable, and should ultimately allow it to compete on cost with fixed wind, according to the Carbon Trust’s James.
“Floating wind is going to be more expensive than fixed wind for at least the next five years, and probably the next 10 years, but the costs can certainly come down,” he said. “Certainly by 2030, there are studies to show it should start to reach parity with fixed wind.”
But floating wind will only succeed if it is given the right support, he argues. In the past the technology has suffered somewhat by being placed in the same category as fixed offshore wind. Instead, it needs to be treated as a separate technology in its own right, with its own support mechanisms put in place.
But if the technology is given the support it needs, the Hywind plant could be the first of many wind farms floating off our shores.
So the UK now has 5GW installed capacity of wind. Does anyone know what the productive output averages?
I raise this because I spent yesterday looking at the Liverpool Bay windfarm with its row upon row of turbines, none of which was actually turning.
5GW of offshore wind, there is more onshore. Offshore is circa 43 to 53% load factor compared to a coal plant at about 60 to 70%. Offshore wind will improve to low to high fifties as better resources are exploited. Not as high as coal and nuclear, but a lot better than PV and onshore wind.
http://energynumbers.info/uk-offshore-wind-capacity-factors has the answers you seek.
“A pilot Hywind device, installed off the coast of Norway and equipped with a 2.3MW Siemens turbine, has operated successfully since 2009, making it the world’s first full-scale floating wind turbine, according to Elin Isaksen, spokesperson for Statoil. In that time, it has generated around 35GW of electricity.”
I am sorry, but the turbine has NOT generated 35GW since 2009, maybe 35GJ or 35GWHours. I expect my introductory physics students to keep power and energy straight.
Thanks for pointing out the error Emmett. That’s been amended now.
That makes it clearer: the average output from the pilot wind turbine is about 22% of its rating. How does that compare with the claims in the article that floating offshore wind turbines have the advantage of stronger and steadier winds?
Hello readers , a short answer is YES , the floating turbines will reshape for sure the entire offshore wind energy . When will apare the next generation of wind turbines everything will be change in good sense .
These certainly sound good ideas to rid ourselves of fossil fuel generation and provide energy independence at last.
But apart from building, tethering and maintaining them many miles offshore, what is the cost of delivering the power to the grid? 15-20km of undersea cables capable of transmitting many MW from a wind farm is not only a substantial cost but also a security issue. It will therefore need continuous monitoring against accidental damage and malicious sabotage. On-shore facilities are a lot easier to manage in this respect.
More white elephants needing massive subsidies “for the forseable future” as the man says.
Let the Norwegians develop this as they have the hydro back-up that is needed for unreliable sources of power: the battery suggestion is another funding sink.
The UK is not a leading developer of Wind power: all the technology is imported.
No its not – try taking a look at where Siemens Wind Power does its research (Clue: Manchester, Sheffield, Leeke and Newcastle) and is starting to manufacture. Why do we always put British engineering down??
“…Let the Norwegians develop this as they have the hydro back-up”
And they have a wealth fund of £800 billion to invest: their share from North Sea Oil.
We have ‘the legacy of the grocer’s daughter….”
Well said.
“….apart from building, tethering and maintaining them many miles offshore, what is the cost of delivering the power to the grid? 15-20km of undersea cables capable of transmitting many MW from a wind farm is not only a substantial cost but also a security issue.” …but we are finishing two-multi-football-pitch sized pieces of UK territory to sail the seven seas: and four lumps of steel (albeit the most important pieces will come from France) that will be able to go ‘under’ water. So surely all this skill and ability can now be turned into mechanisms to look after floating wind-farms: to ensure that the lights are kept on (surely the major interest to the lives of the majority of our fellow citizens) rather than the egos of a few of the conflict groupings.
High altitude wind power (250 à 2000m) turbines are advancing and offer a very good ERoEI (Energy Return on Energy Invested) compared to (floating) towered bladed turbines. KiteGen (Italy) seem to be one of the better designs with a 3MW model being developed, well developed launching system, onground generators, and a semi solid wing. Suitable dense configurations to match conventional wind farms have been developed… see http://euanmearns.com/high-altitude-wind-power-reviewed for a good discussion.
All too often proponents of renewable resources & distributed generation fail to realise that powering a country sized grid demands country sized arrays.
Floating turbines offer at least the possibility to do just that. Fixed turbines & PV panels may be cheaper but between people & radars not wanting their view spoiled & areas with suitable geography, there isn’t much room to expand arrays to cover a significant fraction of the UK. If these floating installations work out it would allow operators to safely locate very large arrays far from view almost anywhere the wind is suitable.
There are a number of point of issue with the continued development of wind energy extraction.
1) Wind predictability no matter where the turbine is located
2) Floating units have an added base energy cost for the raft and what happens when a floater breaks free.
3) The sales gimmick of expressing out put in term of houses. If this is the only way forward state what is a typical house demand. Better would be to show wind contribution against national demand and when was the wind produced energy ref the national demand profile.
4) better than wasting vital resource on an unpredictable energy supply lets focus on tidal turbines were we can predict the long term outcome supplement/ combine this with SMR’s similar to URENCO’s U-Battery and locate were needed.
The Engineer’s overview of a nascent sustainable power industry and energy storage doesn’t even enter the equation? That simply means nobody involved has a clue how to develop the technology we need to make all this new stuff work efficiently. That’s a great shame, since these resources will never run out. We must integrate wind with wave + tidal. Energy storage will facilitate that, if we adopt Smart floating designs and build a BIG barrage or two. (not some piffling lagoons)
“Offshore wind could theoretically provide about four times the amount of electricity generated on the American grid today from all sources.” – New York Times. To hell with the theory, what about the practical? For less than the (long term) cost of nuclear, tidal + wind + wave power would be able to generate all the dispatchable electricity the UK will ever need. The three main problems – over-capacity, intermittency and curtailment – all go away, along with all the costs:-
“Eggborough and Fiddler’s Ferry coal plants to get £77m to be on winter standby.” That’s how the ‘capacity market’ works, in a world where neoliberal lunatics have taken over the asylum.
I outlined the way forward for Fukushima three years ago:-
http://www.nippon.com/en/views/b01506/
NB: The FORWARD consortium is entirely Japanese, a collaboration of government, universities and major corporations. Compare that to our similar projects, which are only ever of interest to UK politicians, if ‘inward investment’ is attracted. That’s code for – “It’s too risky for public money or our friends in the (so-called) ‘investment’ banking industry.” The ‘economic’ mantra is; “Rdd&d of innovative, disruptive technology is none of our business.” Statoil spends without any prospect of a return on investment, and when you set out with the wrong design premise you end up with a white elephant. The US looked at Hywind and turned it down.
The USA and Japan both cite the UK as the leading nation for offshore wind, but leading where? I think current designs still aren’t fit for purpose. We’re up a dead-end creek without a paddle.
The UK wind industry currently has 6,967 Industrial turbines ≈ 14.2GW capacity (Oct 2016 ) deployed.
At 09:00 this morning they were producing just 1GW…
Giving an instantaneous capacity factor of 7%.
So where’s the other 13GW we’ve paid billions for ???
Yesterday I drove past the 288MW 166turbine Gwynt y mor wind farm….none were producing.
At 09:00 this morning they were still a parasitic load, drawing power from the grid.
In fact, Europe wide there is almost no power coming from wind because of a high pressure whether system
See your local Windfarm instantaneous output on this interactive Europe wide map
http://rwe-renewableslive.com/#/map/EU
(Shows
– live production in MW ( A minus figure indicates they are drawing from the grid to power the turbines.)
– Installed capacity in MW (nameplate)
– Graph of last 24 hrs
See UK’s instantaneous energy mix & history http://nationalgrid.stephenmorley.org/
Why do we keep repackaging the same inappropriate technology (which ALWAYS needs ‘the right support’)…& expect different results ??
Hi John,
How easy it is: Insanity (definition) Repeating the same action expecting a different outcome.
Big propeller wind turbines are definitely not the answer. Some vested interests have the ear of the Mandarins of Whitehall and live off the funding.
This island with enourmous tide potential, Severn estualry, Morcombe Bay to name but two, were proposed to be tapped decades ago. However, no government will commit to investments beyond the horizon of the next election.
Ouch!
Thanks for the great links, good sources are always valuable. It is a pity that more of our commentators and press do not examine the facts: however they are primarily arty-types and numbers are dirty / difficult to them. What is unmissable in these summaries is that wind power is even more unreliable than it is often reported to be!
I’ve looked at the output of various wind farms, onshore, in East Anglia. Having done a few calcs. the amount of wind necessary to work the turbines to their best efficiency, only occurs around 8-10% of the time. This indicates a maximum efficiency of around 18 – 20%, and there are always several stopped for “maintenance”.
How can we make sure the Government sees the facts, instead of the bullsh*t, and stops subsidizing the bullsh*tters.
An objective assessment should be made of the efficiency of producing wind power. This should be carried out, independent of the companies that make their profits from the turbine and power generation sectors, (maybe independent engineers).
Someone has to make the Government understand that the present systems for wind power can, and never will, meet their expectations.
I suspect that nothing will change in the near future, there are obviously deals in place which are not necessarily public knowledge.
Perhaps Tidal Generation is a far better option, but it is politically sensitive, yet has the potential to generate large amounts of power, and, by careful water management, 24/7. Tidal generation is also not as “showy” and obvious as damn great windmills.
Your figures (which many would debate) are for onshore; the offshore statistics are very different.
Stuart,
The figures for the wind speed necessary, came from within the wind generation industry itself. The actual wind speed weekly averages, came from the Met. Office!
I know the situation for offshore is different to onshore, but the Government was “conned” out of huge sums of money for onshore, I suspect the same is happening for offshore. I can’t find any genuine unbiased numbers for offshore generation either, it does depend on who supplies the information, and what their involvement is.
I’ll keep searching!
Engineer’s editorially ignorant imPRopaganda advert appears again 3 weeks after its dateline for no purpose other than hope that home hammering will suffice to switch on their loonydon lights, never mind its nonscienced nebulosity nor the excruciating expense to poor old pursey public materially milked to tune of £20Bpa in taxtaken pumpishment of which 5% orso is squandered on campus cabals colluded by burgeoning bureauggery during decades of decimation in engineering expertise on achievable actualities!
Might I propose that there has to be synergy between the self-setting and reefing systems for sails on yachts: and that necessary to protect floating-wind-farms wherever they are to be sited. Indeed one could imagine them ‘gathering back into ‘harbours’ when the weather is too bad for their exposure to such?
It is interesting to note that the 3 leading wind-power countries in Europe are Denmark, Germany then the UK. The highest cost electricity is in Denmark, then Germany then the UK: correlation or coincidence???
The UK is the only one of these 3 countries who pay other countries for the technology and give subsidies to suppliers from Denmark and Germany to provide us with expensive, unreliable power.
Wind power without storage has always been a nonsense and the large number installed is entirely due to Governmental (i.e. our) subsidies.
….but the Government was “conned” out of huge sums of money for…
Of course they were and always will be! They -the toffs of the Establishment-the Westminster bubble -and that is from left and Right (and North & South for that matter)- have not a clue about the technology into which they are shovelling ‘our’ money: and even if they did, would it stop ’em wasting in? Not if it means they win the next ‘con’ (election?)
Let’s see how these work.
Best comment above: “build a BIG barrage or two (not some piffling lagoons)” I was present at one of Hafren’s lectures a few years ago, the day their “rug was pulled”.
& referring to the Norwegian N Sea Oil fund, what can we expect here when politics-speak for “spend” is “investment”? And “save” (when it works, rarely) just means cutting costs?
The simple fact is that all these technologies to many tons of concrete steel and the like for the tiny output they produce. Add to that the need for low-cost storage for days, weeks or months, and they haven’t got the proverbial snowball’s chance in hell.
All It represents is a way of extracting money from poor people and giving it as subsidies to rich people who can afford to fund these monstrosities and reap in the profits.
As opponents of windpower, and renewables generally, often bring up the subject of subsidies as part of their diatribes perhaps we ought to bring to mind the subsidies available to the fossil fuel and nuclear industries. I don’t have any figures to hand but I think you’ll find the comparison illuminating. Perhaps someone with more time on their hands could furnish us with the information.
Supporters of renewables always bring up the idea of subsidies for the fossil fuel and nuclear industries but very rarely have time to give details. I wonder why? Did Norway generate a fund of £800 Billion from it’s oil industry by subsidising it? How does the 3p per kw hour decommisioning cost for the UK’s nuclear industry (the estimated cost devided by the lifetime electricity production) compare to the subsidies given to renewables?
Best regards
Roger
Does your 3p/kWh include the cost of keeping the high level waste produced by decommissioning contained for 100,000 of years? Yes Norway did subsidise its oil industry at times. It was also not lead by a fanatic who deliberately destroyed much of British industry in pursuit of her ideological goals.
My figure is based on the usually quoted £72 Billion cost of decomisioning the UK’s current NPPs and all the legacy waste from atomic weapons manufacture.
High level (activity) nuclear material does not have to be stored for 100,000 of years. By very basic physics the higher the activity the quicker it decays. This is why used nuclear fuel rods are initially transfered to the nearby pool whilst the high activity products decay. When the heat output has dropped to a suitable level they are moved to dry storage. It is also why the core assembly of a NPP is left in place for 10’s of years after the rest of the plant has been demolished .
Best regards
Roger
So what happens when four of them sink? Quatro Sinko?