With 80% of the world's best wind resources located in deep, open waters, floating turbines could prove critical to harnessing the most from clean offshore power
Equinor's Hywind project in Scotland is the UK's first venture into floating wind turbines (Credit: Equinor/Øyvind Gravås/Woldcam)
Floating wind turbines are under development around the world, opening up opportunities for wind power in areas of deep water. World Wind Technology writer Will Moffitt talks to Stephen Bull, Equinor’s senior vice-president for wind and low-carbon development, and Marc Costa, director of the Renewables Consulting Group, about the potential it offers in the global shift to renewable energy.
Stephen Bull is a man deeply connected to “the energy transition story”. On one level, this phrase could be used to describe Bull’s personal journey from trader to renewable energy expert – a move fuelled by a desire to “move away from the more abstract world” of financial systems to the nuts and bolts of large-scale offshore wind projects. “I think hands-on engineering major-scale projects is where I found my niche,” he says.
It’s also a narrative imbued with history and symbolism. “[We’ve] always been looking at transitions,” he adds. “For centuries, we moved from coal to oil, then from oil to gas and then, going back hundreds of years, from biofuels and collecting food in the forest.”
A new chapter was penned during what Bull describes as the “energy revolution” of the 1970s and 1980s, when the Organization of the Petroleum Exporting Countries (Opec) in the Middle East pulled the plug on black gold – forcing nations such as the US and Denmark to experiment with renewable forms of energy, such as wind-powered water pumps and solar systems.
While these developments were modest, they stirred the blades of the turbine, igniting efforts to build solar grids and larger wind farms to power electricity in remote areas.
Floating wind turbines will play a role in a rapidly-growing offshore sector
As senior vice-president of wind and low-carbon development at Equinor, Bull is now taking this energy narrative a step further. He is overseeing a variety of offshore projects all over the globe, looking at cheaper forms of technology and higher government subsidies that can propel the wind energy industry forwards.
According to National Geographic, turbine use has increased by more than 25% per year in the past decade, and cumulative wind capacity grew from 17,000 megawatts (MW) to 430,000MW between 2000 and 2015.
While wind remains a minority energy source, Bull is adamant that it could be lucrative, particularly in offshore locations where high wind speeds can whip up plentiful returns on investment.
“It’s a huge opportunity for the future, with immense global opportunities, not just in Europe and the US East Coast, which is currently the market today,” he says, citing a recent report by International Energy Agency (IEA), a Paris-based organisation, which valued the future offshore wind market at $1tn.
With the right technology and governmental backing in place, the report predicts that offshore wind has the potential to provide sufficient electricity for every living person across the globe 18 times over.
Around 80% of the best wind resources are located in deep, open waters
Scratch the surface of those figures, however, and it becomes apparent that this grand vision will only be met by utilising floating wind structures – turbines that can operate and remain stable in areas of deep water, capturing pockets of wind energy that can be transferred back to the mainland through a snaking network of inter-array cables.
“The key thing about floating technology is that it reaches markets that fixed-bottom projects can’t get to,” Bull says. “Anything more than roughly 60m in water depth is too expensive or challenging for fixed-bottom structures. Floating wind covers that, but what’s important is the size of the prize.”
It’s a considerable bounty, with 80% of the world’s best wind resources on offer in vast areas of open water, such as the North Sea, which has attracted considerable attention from Equinor and other companies which are seeking to build on its 220,000 square metres of untapped space.
UK offshore wind industry is working with North Sea floating turbines
Sitting on the UK coast’s icy edges – in places such as Sheringham Shoal in the east and Peterhead, 18 miles shy of Aberdeenshire in Scotland – is the UK’s next line of offshore wind farms; islands of turbines that can harness wind speeds reaching 142mph.
While Sheringham Shoal is a fixed offshore installation, Hywind – based in Peterhead – is the UK’s first deep-water floating wind farm, a £152m ($190m) project that Bull and Equinor have been working on for 15 years.
A closely-correlated formation of five steel towers swaying at sea, its turbines are kept in place by semi-submersibles and spar-buoys that rely on floating pontoons moored to the seabed through a series of long steel chains.
With each 175m tower comfortably dwarfing Big Ben, and turbines with the blade span of an airbus, Hywind is a gargantuan experiment – one that is functioning exceptionally well in fierce conditions. While the typical capacity for fixed-bottom offshore wind farms is anywhere between 45% and 60%, Hywind has operated at 65%, a feat achieved in spite of severe storms and a hurricane.
“You see lots of demos all over the world, whether you’re in Portugal, Japan, or France where they’ve developed the technology and [are] testing it for the conditions, and monitoring it over time. But this is the first time we’ve actually put together an array of five [floating] turbines together,” Bull explains.
The result is a project capable of producing 30MW of energy, a total that Equinor says could theoretically generate enough electricity to power 20,000 homes, with any unused energy stored in lithium batteries for later use.
Successful development of floating wind turbines will require help from government subsidies
While these numbers pale in comparison to fixed offshore projects – once completed Hornsea 1 should produce six gigawatts (GW) – it’s a small, significant stab in the right direction, a blueprint that future projects can build upon, if they can get the financial backing.
While Hywind is an exciting experiment, the problem of competing in the same slipstream as fixed-bottom projects remains, particularly in the UK where the contracts for difference (CfD) auction system inevitably favours cheaper technologies.
Dogger Bank Wind Farm, a high-tech offshore project that Equinor is co-developing with SSE Renewables, stands as a stark reminder of the financial disparities that exist between floating turbines and those further offshore.
“Dogger Bank came in at a price of £39 ($48) to £41 ($51) per megawatt hour (MWh). We can’t compete with that for floating wind, the technology and the climate isn’t there yet,” Bull says.
To get even, Bull and other floating evangelists, such as RenewableUK and Scottish Renewables, are advocating something called an innovation CfD. A separate pot for investment in renewables such as floating wind turbines and tidal streams that would enable these premature technologies to develop and, ultimately, prove their worth.
“At a certain point it becomes unfeasible to run these deep-water projects,” Bull admits. “If [somewhere like] Scotland wants to reach its renewable targets it needs to have an opportunity to develop floating wind.”
Marc Costa, director of the Renewables Consulting Group, argues that without this financial backing, a considerable number of these projects are destined to drown in their own ambition. “During early-stage projects, you need to have a subsidy, because otherwise you will never be able to compete with a fixed bottom,” he says.
He points to the current CfD allocation system, where fixed subsidies are awarded to projects for a 20-year period. “Two years ago, we were all setting targets for 2020, saying that we’ll see bids for £100 ($125) an hour,” Costa explains. “We are now seeing well below half that amount because there were other [fixed-bottom] projects in the pipeline, so constructors and project developers could see ways to be more efficient.”
Equinor’s Hywind Tampen floating wind turbine project is an industry front runner
While campaigning for a fairer CfD model would swing things back in favour of floating offshore structures, larger turbines would also help to level the playing field, generating more power and income.
“People don’t realise that we need to build giants in the middle of the sea. The moment that we see larger turbines being technology ready, things could change,” Costa says. “The chances are that by 2020 we will see 16 to 18 megahertz (MHz) machines that could offset the costs of the cables and the sub structures.”
Until these larger structures are available, convincing more energy companies to embrace renewables could be a key driver for floating wind. While Equinor remains a front runner in this slowly-developing field, Shell’s recent acquisition of engineering outfit LV indicates that large petroleum companies might be waking up to the benefits of linking their technologies to floating resources.
As other companies seek to diversify their portfolios and experiment with these novel energy solutions, leading the way is Equinor. In October 2019, the company announced that it was submitting plans to the Norwegian government for Hywind Tampen, an 88MW wind farm that will be built at the Snorre and Gullfaks oil fields in the southern tip of the Norwegian Sea.
With 11 8MW turbines installed on spar buoys, Tampen will be the first ever oil and gas platform powered by a floating offshore wind farm, located 140km from shore and in water up to 300m in depth.
By harnessing the power of floating turbines, this project – due to be completed in 2022 – could cut carbon emissions by more than 200,000 tonnes per year.
“It means that we can turn off some of our gas turbines because you need consistent power the whole time on a platform,” Bull says. “It reduces CO2 emissions – ultimately, the business case for that is that it can reduce CO2 taxes offshore.”
Economic merits of offshore wind will drive sector development
As someone who has worked in oil and gas for decades, Bull knows that when it comes to these kinds of transitions, moralising must be kept at bay. Instead, the galvanising energy story is an economic one.
He cites the “enormous carbon footprint” of Canada’s oil sands development and heavy oil produced in Venezuela. Due to high rates on carbon tax, he argues, these projects will soon become infeasible.
“High CO2 taxes in the future will reduce or impinge on heavy oil production – taxes work because they’re hitting people where it hurts. If people are making the wrong economic choices, then that does change behaviour,” Bull says. “Of course, there’s a moral element to it, but I don’t think that is the part that gets people moving.”
For a man who specialises in transitions, getting people moving is now Bull’s primary job. In a few hours, he is set to fly to Philadelphia for a meeting to discuss Empire Wind, the company’s first significant offshore wind project in the US.
Upon completion, this 816MW project, which spans 80,000 acres south-east of Long Island, will power 500,000 homes. While this ambitious undertaking is occupied by fixed turbines, the seemingly endless stretches of California coastline are ideal foundations to build the US floating wind revolution.
“I think the length of the California coast, particularly as you see the electrification of the vehicle fleet, looks like a good long-term market,” Bull says.
Floating offshore wind approaching a promising decade
While the UK, Norway and France continue to lead the way in the floating wind sector, South Korea is also showing great potential with plentiful areas of deep water, well-established oil, gas and shipping industries, and a government seeking to diversify the country’s energy programme.
Buoyed by these developments, Bull is confident that the global floating wind sector will grow in the next decade, with five to seven major offshore floating wind projects spurring on further investment and convincing other nations to follow suit.
“Getting major-scale global projects will reduce the cost dramatically, and potentially inspire other countries to open up to it. At the moment we’re on the cusp of a really exciting area,” he says.
With 80% of the world’s best wind resources on offer, floating wind represents an exciting new chapter for renewable energy, with an influx of projects set to be constructed around the globe in the next decade.
While challenges remain, not least acquiring further investment and larger turbines, these swaying structures located far out to sea could fundamentally alter how electricity is generated, marking an exciting new chapter in an age-old energy transition story.
This article originally appeared in the summer 2019 edition of World Wind Technology. The full issue can be viewed here.