Head 10 miles out from the coast of Aberdeen in Scotland and a cluster of five giant wind turbines spin at a height of 190 metres above the North Sea, quietly generating enough clean electricity to power about 35,000 Scottish homes.
This offshore windfarm is dwarfed by the sprawl of turbines rising from the sea along Britain’s east coast. But the Kincardine project represents a different future for clean energy: when its turbines began spinning it was the largest wind farm in the world that could float.
Each of Kincardine’s giant turbines is mounted on a buoyant foundation, in waters that plunge to depths of 80 metres. While traditional offshore windfarm foundations are rooted in the seabed, floating foundations are tethered to the sea floor by cables, meaning they can be installed in waters of far greater depth.
The work represents an engineering feat of epic proportions. Each of Kincardine’s turbines is mounted on a floating triangular base that stands almost 30 metres above the sea surface, held up by three buoyant columns each about 50 metres apart. The framework includes water-filled cans at two of its points to balance the weight of the turbine, which sits on top of the third.
There are other designs for floating foundations, including a vertical buoyant cylinder stabilised with water, rocks or other heavy materials. These foundations are then tethered to the seabed.
Traditional design may have led the way for the maritime wind revolution of recent years, but it is estimated that up to 80% of the world’s offshore wind resources are to be found in waters deeper than 60 metres, where fixed seabed turbines cannot be built. So while huge windfarms have sprung up in the UK’s coastal waters, making Britain a world leader in offshore wind, engineers have been working to prove that floating foundations could help the technology reach new frontiers in the open sea.
The fundamentals of this technology have been borrowed from the fossil fuel industry, which first began pioneering floating oil rigs in the 1960s. It is little surprise, then, that the leaders in Europe’s nascent floating wind sector are also its biggest oil producers: Norway, the UK and Italy.
By building floating foundations for huge offshore turbines, developers hope to continue expanding the world’s wind power capacity beyond the limits of relatively shallow coastal waters to deeper ocean depths, where wind speeds are also more powerful.
Kincardine’s capacity of 50 megawatts is dwarfed by the 1.32 gigawatt scale of Hornsea 2, the world’s largest fixed offshore windfarm, which lies off the Humber estuary and is capable of powering more than 1.4m homes. Overall, the UK’s floating wind capacity stands at 80MW, the second highest in the world behind Norway, but is still a fraction (0.6%) of the 14GW contributed by Britain’s fixed offshore windfarms.
In the coming decades this is likely to change, even though, under UK government net zero targets for 2030, floating windfarms are set to remain in the shadow of their forerunners, at 5GW capacity, while fixed windfarms mushroom to 60GW.
Expanding offshore wind power is a key element of ministers’ plans to reduce the cost of energy by expanding renewable production. Electricity bills remain well above the levels they were at before Russia invaded Ukraine, and last Friday the electricity regulator for Great Britain, Ofgem, announced that the average annual dual-fuel bill would rise again by 10% from October to £1,717.
Earlier this month, the crown estate, which owns rights to the seabed off the British coast, invited pre-qualified developers to set out their plans to deliver three floating offshore windfarms in the Celtic Sea. By approving the plans as part of the application process, it hopes to accelerate the pace at which floating wind facilities can be built.
The industry’s trade association, Renewable UK, believes that by the 2040s, floating offshore windfarms will represent well over half of the UK’s offshore wind generation.
“Floating offshore wind is the future for offshore wind,” says Jane Cooper, the director of offshore wind at Renewable UK. “It’s the natural progression. It has the potential to enable the UK to take a giant step forward by building the next generation of projects further out to sea, in deeper waters where wind speeds are even higher.”
This mooted step change for the offshore wind industry will not be without its challenges. Recently there has been a wave of financial turmoil for developers after soaring cost inflation and higher interest rates collided with supply chain disruptions to upend construction plans across the industry.
Danish developer Ørsted announced on 15 August that it had been forced to delay a major project off the north-east coast of the US, months after cancelling two nearby developments and cutting hundreds of jobs.
For floating offshore wind, the greatest challenge is cost. This is laid bare in the guidelines for the government’s upcoming auction for clean energy subsidies. That sets the maximum price for developers of fixed offshore windfarms at £73 per megawatt hour; for floating offshore developers, the figure is £176 per MWh.
The Norwegian energy company Equinor, a leader in developing floating windfarms, believes that, with the right policy support, the cost of floating windfarms could align with their fixed counterparts by 2040 – in time for the expected boom in floating projects across Europe and around the world.
For the UK, the second challenge lies closer to home. Britain’s ports are too small and under-resourced to accommodate the huge dimensions of the turbines and floating foundations required to meet the government’s ambitions. Billions in investment will be needed to make ports bigger and deeper, while upgrading their facilities to allow for manufacturing and assembling the gargantuan infrastructure required.
Britain’s first floating windfarm, Hywind Scotland, is in the Norwegian port of Wergeland for the summer for maintenance work which could not be completed in the UK. The decision to tow the turbine foundations across the North Sea was branded a “missed opportunity” by Scottish Enterprise.
“We need to attract £4bn of public and private investment in new port infrastructure to accommodate floating wind by the end of this decade,” said Cooper.
“This would drive £18bn of wider economic activity throughout the UK, and by 2040 the floating wind industry could support 45,000 jobs.”
The UK wind industry is anxious to grasp the industrial opportunity presented by the emergence of the new technology to help countries that have less hospitable coastlines for fixed turbines – such as Portugal, Japan and the US – to expand their wind power generation.
One early British success story is Bristol-based Rovco. The subsea surveying and robotics company has emerged as one of the UK’s fastest-growing startups in recent years thanks to its digital approach to providing data solutions to offshore wind developers including SSE and Iberdrola. It is expected to reach “unicorn” status – a valuation of more than $1bn – later this year as it seeks more funding to help finance its global expansion.
Brian Allen, the chief executive of Rovco, says wind offers “a huge, bright future for our business”. He adds: “If you look at where we were in 2014, there weren’t very many offshore windfarms out there. But the huge technology leap and economies of scale that have been achieved in the past 10 years are the evidence of what we can achieve in floating offshore wind in the decades ahead.”
The pace of the change ahead is likely to surprise many, Allen says.
“Most people I speak to, who ought to know this, just don’t understand how big an industry [floating wind] is about to become. Most of the areas where the industry expects to develop offshore wind are in very deep water, and these windfarms will need to float.
“Even though the UK is literally the world leader in developing offshore wind, people genuinely have no idea. It’s coming like a freight train but people are blind to it.”
• This article was amended on 26 August 2024. An earlier version described Kincardine as the world’s largest windfarm that can float. This was the case when it opened, but it has since been surpassed by the Hywind Tampen project.
