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The continuous trend of larger turbines, often installed further

offshore and in deeper water, pushes conventional foundation

types to their boundaries.

Currently, the majority of offshore wind turbines are installed on

monopiles, a more economical solution than expensive jacket

foundations for shallow water depths.

However, recent and near future monopile designs have reached

unprecedented weights and diameters. With only a few factories

capable to manufacture and a few vessels big enough to install

these XXL-monopiles, it is clear that the supply chain is struggling

to follow the trend of ever increasing foundation sizes.

This struggle is further underlined with the newly announced

8-10MW turbines for which water depths up to 60m are required.

THE CHALLENGE

MINI JACKET

MINI JACKET

TWD developed a foundation design, consisting of 3 mutually con-

nected inclined piles; called the Mini Jacket. Because individual

lifts do not exceed 450t, a typical 8-10MW foundation can be ef-

fectively installed by the majority of existing installation vessels.

This reduces installation costs and re-opens the foundation instal-

lation market for smaller, currently outdated vessels.

For these larger water depths, the inclined legs are structurally

more efficient than a monopile, resulting in a significant founda-

tion weight reduction. Besides that, the amount of complex steel

is minimized compared to conventional jackets. In both cases this

results in a fabrication cost reduction up to 30%.

THE SOLUTION

GET IN TOUCH

WWW.TWD.NL

TEMPORARY WORKS DESIGN

T

W

E

+31 10 294 03 74

www.twd.nl

info@twd.nl

Rotterdam Science Tower - Marconistraat 16

3029 AK Rotterdam

The Netherlands

MINI JACKET

The foundation allows for effective stacking on the vessel’s deck,

such that more foundations can be transported per trip. At the

installation location, the top segment is supported by a hang-off

frame over the side of the jack-up barge. After upending, pitching

and driving the piles through the inclined sleeve, a fast swaged

connection permanently connects the piles to the sleeves. Be-

cause there is no need for a separate piling template, the installa-

tion campaign can be done with a single vessel.

The turbine tower can be mounted directly on the Mini Jacket’s

central flange interface in a separate installation campaign.

THE INSTALLATION METHOD

The Mini Jacket design is fully certified, and can be adjusted to

your specific requirements. For pricing information or technical

enquiries, please make use of the contact information below.

AVAILABILITY

Design is scalable for higher turbine outputs and

water depths, within the current capabilities of the

supply chain

Modular design can be installed with majority of

existing fleet

ADVANTAGES

Smaller components simplify the foundation’s

logistics and open-up new fabrication, storage and

supply scenarios.

The three inclined piles are structurally more effi-

cient than a single monopile, resulting in a signifi-

cant weight reduction

Single installation campaign, no pre-piling required

Stacking of foundations on deck allows to make

maximum use of available pay-load