Floating offshore wind has “massive” potential, says an expert in offshore structures at London Offshore Consultants, but the logistics of building floating windfarms will be very different from that required for bottom-fixed units
Floating offshore windfarms have come to be seen as the ‘next wave’ in the development of offshore wind energy. Several demonstration projects, a number of which are highlighted below, are getting underway, but despite the many potential advantages of floaters, there remain numerous challenges to overcome.
Speaking to OWJ in early April, RV Ahilan, LOC Group’s director, renewables advisory & energy, said he foresees “dramatic” potential for floating offshore windfarms – potentially hundreds or even thousands of gigawatts (GW) of capacity in countries as diverse as the US and Japan and in countries in the Mediterranean where the water depth excludes fixed foundations – but says the industry will need to adopt a new approach to infrastructure and logistics if large-scale floating offshore wind is to become a reality.
“Floating offshore wind opens up vast areas for potential development,” he said, “areas in which the wind resource available is much cleaner and more reliable than near-to-shore bottom-fixed windfarms.” They present an opportunity to operate a new generation of much larger, high-capacity turbines in a ‘sweet spot’ where capacity factors are much higher than bottom-fixed turbines and there is less shielding of turbines by other units in an array.
“Capacity factors for a fixed windfarm are in the order of 40%,” he explained. “For floaters, capacity factors will exceed 50%, but one of the big challenges is going to be port infrastructure that can handle floating foundations, which will be much larger than those for bottom-fixed units that the industry has grown used to handling. The footprint of a floating foundation could easily be five to six times that of a fixed unit. How many ports can handle units that size? How many have sufficient craneage?”
In contrast to the potential challenges of building and floating out massive floating foundations, maintaining them at sea ought to be easier, he says. Ships stationed offshore or fixed structures could accommodate turbine technicians. But mooring such large units will also be a challenge. The offshore oil and gas industry has experience of mooring large structures but not of mooring dozens of them in close proximity. In a 500 megawatt (MW) windfarm, there will be potential interference between moorings. At the same time, he suggests, it might be possible for floaters to ‘share’ moorings.
“Electrical array cables are another area where a lot of research and development will be required,” said Mr Ahilan. “The industry has had great success getting a cable from a fixed foundation to an array and bringing electricity ashore, but new solutions will be required to reliably connect floating units to an array.”
Overall, he says, the industry needs to begin thinking now about how assembly lines for floating foundations might be established, where they might be built and how they will be handled.
Against this background, demonstration projects are moving ahead, among them one led by Irish renewable energy group Gaelectric, which has partnered with floating offshore wind specialist Ideol to develop floating offshore wind energy projects in Irish waters using Ideol’s patented ‘Damping Pool’ technology.
Gaelectric and Ideol are investigating several sites in Irish waters for short-term precommercial and long-term commercial-scale projects, with an initial objective to develop a 30 MW plus turbine array project, followed by a multigigawatt commercial-scale extension on both Irish coasts.
Ideol’s Damping Pool concept is at the heart of multiple demonstration and precommercial floating offshore wind projects in France and Japan, including the Floatgen project currently under construction off the Atlantic coast of France near Saint-Nazaire. Gaelectric is one of Ireland’s leading renewable energy and energy storage groups.
Gaelectric founding shareholder Brendan McGrath said “In Ireland, we are blessed with significant reserves of wind energy, which are having very tangible impacts in driving energy prices down and improving the sustainability of electricity generation. The development of onshore wind projects is well understood.
“However, the potential for offshore generation is enormous and holds the prospect of significant benefits for Ireland. Offshore wind speeds are faster and more consistent. We should also be able to deploy larger turbines with the prospect of moving up to 10 MW turbines from the onshore levels, which are currently in the region of 2–3 MW.”
The Irish Government’s Offshore Renewable Energy Development Plan has identified a potential for the generation of 27 GW from floating offshore wind in Irish coastal waters. Gaelectric says Ideol’s floating foundation technology “opens up the prospect of creating an enduring, sustainable indigenous industry along the west coast and provides Ireland with the opportunity to rebalance available job opportunities while creating a significant energy hub in western towns and ports”. A fully commercial-scale offshore project of 500 MW capacity based on Ideol’s technology has the potential to create up to 2,500 construction jobs with a further 200 in maintenance.
Earlier this year, the Dounreay Trì floating offshore wind demonstration project off the Scottish coast was granted planning approval by Scotland’s minister for business, innovation and energy Paul Wheelhouse. The two-turbine demonstration project will be located approximately six kilometres off the Caithness coastline. Approval came after the recent approval of the Kincardine floating offshore windfarm and last year’s consent of the Hywind Scotland pilot, which means Scotland has now agreed planning permission for up to 92 MW of floating offshore wind.
Mr Wheelhouse said “Once operational, the demonstrator project will help to develop this pioneering technology and cement Scotland’s reputation at the forefront of innovation in the renewables sector. This not only highlights our commitment to exploring this innovative technology but offers real scope for the development of wind energy projects in deeper water, in Scotland and across the world.
Responding to the news about Hexicon’s project, Lindsay Roberts, senior policy manager at Scottish Renewables, said “Hexicon’s Dounreay Trì is another ground-breaking project for Scotland’s renewable energy sector and shows how our natural resources and skilled supply chain are proving attractive to businesses from across the globe. Scotland is home to approximately 25% of Europe’s offshore wind resource, and we are now starting to build out projects that will harness this potential. The Scottish Government has shown its ambition to generate the equivalent of half of all energy consumed from renewable sources by 2030, and offshore wind can play a key role in meeting that ambition.”
The floating development by Kincardine Offshore Windfarm Ltd will support the creation of around 110 jobs during assembly, installation and through ongoing operations and maintenance activities. It will have a generating capacity up to a maximum of 50 MW. Mr Wheelhouse said “Once operational, this pioneering, 50 MW windfarm will produce enough electricity to power almost 56,000 homes and will create jobs and investment across Scotland through the use of our supply chain. It will also cement our place as one of the world’s leading nations in the innovation and deployment of floating offshore wind. If the technology can be demonstrated at scale, it has huge potential to help Scotland meet its energy needs and to develop a supply chain that can service opportunities elsewhere in Europe and in markets such as Southeast Asia and North America.”
Research undertaken under a joint industry project to test and qualify synthetic mooring ropes for floating offshore windfarms suggests that they work and that they would be less expensive than conventional mooring solutions. The joint industry project (JIP), which was funded by the Scottish Government and administered by the Carbon Trust under the Marine Renewables Commercialisation Fund, combined the efforts of nine European organisations with the objective of testing and qualifying new, synthetic mooring components. After being successfully tested, nylon has been qualified for permanent application and has confirmed its cost-saving potential. “In comparison with expensive and heavy conventional chain-based mooring systems, the use of nylon can be considered as a cost-effective solution in shallower water depths,” said the project partners.
The JIP, which consists of Tension Technology International (project leader and expert in synthetic rope development and testing), rope manufacturer Bridon International, Ideol, which develops floating foundations, Bluewater Energy Services (bringing an end-user perspective in floating tidal), DNV GL and Lloyd’s Register (LR) was set up to qualify nylon via a rope-testing programme so that it can be deployed safely and certified for permanent moorings.