The first industrial-scale versions of Universal Foundations’ (UF) next-generation suction bucket foundation are to be installed off Germany as part of an annex to the 252MW Deutsche Bucht offshore wind farm, following finalisation of a breakthrough agreement with Canadian developer Northland Power.
Project engineering for the units, which will be topped with 8.4MW MHI Vestas V164s, will kick-off early next year, with plans to move into fabrication at the Harland & Wolff yard in Belfast, Northern Ireland, on a timeline that would see installation offshore in spring 2019.
“This is a real chance for the technology to fully prove itself,” states Northland’s Deutsche Bucht project director Jens Poulsen. “There is no doubt it will be very well suited for installation off Germany with its more stringent [marine] noise restrictions, and if it shows itself to be a competitive way of installing large-scale turbines offshore there will be a future for it [in other global markets].
“We felt it was an important opportunity to test this technology, further de-risking it at the same time, as well as getting additional production from two extra [turbine] positions at the wind farm.”
UF’s managing director Kristian Ravn states: “This is the perfect pilot site for our technology – two 8MW-plus wind turbines in almost 40-metres water depth and in the [environmentally challenging] German sector. It is the ‘dream project’ for us.”
The Deutsche Bucht project is underwritten by a German government technology development programme backed by national industry bodies BSH and BnetzA that has meant the extra generating capacity could be added to the wind farm for a demonstrator.
Northland and UF are tackling the project – which is also receiving funding via the EU’s Demowind demonstrator scheme – in consortium, with Danish consultancy K2 Management and French investment house Green Giraffe having been brought in to shepherd engineering and financing.
“We’ve put our finest efforts into supporting our partners in winning this development bid. Working closely with Northland Power, K2 Management and Green Giraffe made it possible to position our foundation technology as the enabler to win the award for the 16.8MW extension of capacity at Deutsche Bucht,” says Ravn. “We are thrilled to have this opportunity to show the world what our foundations can do.”
UF business development director Kristian Ascanius Jacobsen adds: “Demonstrators have a hard business case to make [because of their costs]. For Deutsche Bucht, with the extra capacity, this project will be icing on the cake. It also incentivised a closer working together of all partners.”
The UF Mono Bucket concept has been in development since 2001 via prototypes including a 3MW turbine-topped unit in Frederikshavn, Denmark, and met-mast installations at projects including, most recently, the UK’s Dogger Bank mega-development.
UF’s Mono Bucket is one of a family of suction-based offshore wind foundation concepts that have hollow, cylindrical steel feet, which are installed into the seabed by use of suction pressure, gravity and smart installation techniques. Orsted (as Dong Energy) installed a three-legged suction-bucket at the Borkum Riffgrund 1 wind farm in the German North Sea in 2014, plans to install 20 units at phase 2 of the Borkum Riffgrund project, and Vattenfall is also focusing on the technology at Aberdeen Bay in the UK. .
For Deutsche Bucht, the conservatively designed steel units, each weighing 1,100-tonnes, will have a base diameter of 18.5 metres, with skirts that penetrate 16.5-18.5 metres into the project site’s predominantly sandy seabed.
“After the Frederikshavn and Dogger Bank projects, we feel we have de-risked the technology to a point where this [Deutsche Bucht] is the final hurdle [to commercialisation],” says Jacobsen.
“The largest model turbine in serial production, good regulatory conditions and very suitable seabed [suction buckets ‘pull in’ and secure well in sand and clay],” he adds. “On our Christmas lists we couldn’t have hoped for a better site.”
On our Christmas lists we couldn’t have hoped for a better site
“[Suction bucket] technology has come a long way in the past years and it already a well-known technology,” says Poulsen. “In the first instance, we see it as likely to be competitive off Germany [due to noise regulations], but if it can compete [in price with conventional foundations] in the full scope – installation and operation but in many other parameters too – then this will determine its wider success moving forward.”
Offshore wind turbine suction bucket technology – inspired by suction caissons that for decades have been a favourite of the oil industry for offshore platforms – makes a strong economic case as a key foundation concept for the coming wave of construction of the global offshore wind fleet.
The Mono Bucket reduces costs on three fronts. It uses as much as 25% less steel than a monopile so is less exposed to volatile global metals markets; the structure does not need to be piled into the seabed as conventional foundations are, so the environmental impact of suction buckets is minimal – and noise mitigation costs cut; and the speed of installation is much faster, with each foundation being fixed to the seabed in under three hours – a fraction of the time needed for a piled-in structure – slashing the price of offshore construction.
Various studies on the cost-profiles of different foundation designs point to mono-bucket technology as being potentially the lowest cost for 6-8MW turbines in water depths down to 40 metres, as much as 24% cheaper.
While the “focus in the pilot is on showcasing the significant environmental benefits of the technology during installation and the ability to decommission the foundation 100%”, Jacobsen suggests the “new realities” of a zero-subsidy project culture make new-breed foundation designs such as they Mono Bucket an important area to further shave cost out of offshore wind.
“Developers are squeezed and the squeeze is going to get greater. Every one is looking for the golden ticket to win the next bidding rounds [offshore Europe]. Monopiles and jackets might win projects, but the developer who specs them either has to outsmart the other bidders on the financial side or compromise profits.”
Developers are squeezed and the squeeze is going to get greater
“We think we have a cost-out advantage over conventional foundations, especially here in Germany with its high noise pollution regulations.”
Despite the lucrative economics and recent demonstrator successes, the long-standing promise of suction-bucket technology has yet to translate into commercialisation. Poulsen thinks this might change with Deutsche Bucht.
“Since the award of additional capacity from the BnetzA in 2016, the team has made significant progress on this project. Both Northland Power and Universal Foundation have invested significantly to drive the pilot project forward and we are fully dedicated to make this a success.
“Progress has only been possible with the support our respective owners and the constructive interaction with German authorities. No doubt, this project is receiving a lot of support and attention as it is a beacon for showcasing what above state-of-the-art technology can deliver to an industry under both political, economic and environmental pressure.”
Northland's third offshore wind project, Deutsche Bucht, located 95km northwest of the island of Borkum and close to Northland's other German offshore wind project, Nordsee One, is expected to be brought online at a cost of €1.3bn. The wind farm is expected to generate over 1,000 gigawatt hours of electricity per year.