Universal Foundation on cusp of Denmark deal

Next-generation offshore wind turbine foundation designer Universal Foundation (UF) is on the brink of a breakthrough deal off Denmark with a "large, well-known utility" to install a first batch of its so-called mono bucket bases topped with 6MW-plus class turbines, Recharge has learned.

The agreement, which would breathe new life into a dormant  government-consented 50MW demonstration site off Frederikshavn, would see as many as six machines erected in 15-20 metres of water using UF's technology, a bucket-shaped foundation that is vacuum-sealed into the seabed and levelled using hundreds of built-in water jets before being fitted with a turbine.

"The offshore demonstration project is a very open concept right now," says UF managing director Torgeir Ramstad. "It could be several different turbines and several different sized foundations. We don't need the full 50MW for our plans but we could take it on."

Expectations, he adds, are that the Danish authorities will take a decision on a full development plan for the testing site "after the summer" with a European tender to follow for the "main components" for the project.

"We have developed the entire balance of plant concept for this site," says Ramstad. "So it is our hope that the owner will see us as onboard."

Though the mono bucket is designed for waters of between 25-55 metres, the shallower site depths off Frederikshavn "removes only one challenge" from the project. "Variable soil conditions, a very big turbine – there are other challenges. We don't want to stretch too many parameters at once," he adds.

The mono buckets to be built for the demonstration site, located 4.5km offshore, would weigh up to 540 tonnes each and measure around 17 metres in diameter with "skirts" – the rim of the foundation that embeds into the seabed – between 5-12 metres in height.

The UF plan would trial an "integrated" installation strategy where mono buckets and turbines are ferried together to the site by a jack-up vessel, with installation of the foundation "on the first day and of the turbine on the next", cutting installation times "significantly".

Delivery of the inter-array and export cables are part of the package, as well, says Ramstad. Installation of the foundations and turbines would be carried out by Windcarrier, a sister company to UF in the Fred. Olsen group.

"This way you prove the potential of installing a turbine immediately after the foundation compared to monopile-based machines where the grouting of the transition piece has to cure over a long period of time," says Ramstad.

The Danish Energy Agency (ENS), which is working to launch a tender for a tariff of DKr0.70/kWh for demonstration sites, is targeting concepts that have "a clear technological development object aiming at reducing the future costs of offshore wind turbines".

Ramstad says a final investment decision is slated "for September / October time", with the full development switched on by the end of 2016.

UF's mono bucket last autumn completed an exhaustive £6.5m ($10.4m) joint industry trial installation campaign in the North Sea – shepherded by UK government-industry body the Carbon Trust for partners Statoil, Statkraft, E.On and Dong – that checked the suction bucket technology's penetration ability, verticality, water injection impact on soil plug, forces and stress in skirt structure and internal soil levelling capability.

A total of 29 full trial installations were performed in varying soil conditions, returning "very promising results".

A pair of UF suction buckets are currently installed at the Dogger Bank -- a 9.6GW zone off the UK where waters are 18-63 metres deep -- as foundations for two meteorological masts. A flagship mono bucket unit topped with a 3MW turbine has been in place off Frederikshavn, Denmark, since 2002.

The ENS expects the tendering process to run to the end of the year, with go-ahead for the winning demonstration scheme in 2016.