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THE SUCTION BUCKET MONOTOWER

Advantages:

• Estimated low cost

• Ranges from 0-55 meters water depth

• No separate transition piece

• No scour protection necessary

Disadvantages:

• Mounting only in residual soil no roc!s"

• E#tensive welding

• $nstallation procedure not fully conceived

• %ransport vessel design is yet to &e defined

%he suction &uc!et monotower is a new concept' $t is presently installed as a prototype in %he

North (ea and )rederi!shavn* Denmar!' A prototype installation in +ilhelmshaven failed'

%he concept has &een chosen for further demonstration &y the ,ritish foundationar&on

%rust and is seen as a promising concept &ecause of its light construction and afforda&le price

compared to the relatively large water depths it operates in'

%he structure consists of . from the &ottom upwards . a foundation* which is a large cylinder

with a closed top* and no &ottom' %he side on the cylinder is called the s!irt* and the diameter of

this cylinder can &e up to / meters'

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The prototype for Horns Rev 2 site (North Sea, Denmark). It weighs 1! tons, the skirts are 12 meters in"iameter an" meters in height. #hoto$ %a&'org niversity 

1arge &racings connect the top of the cylinder to the monotower' %he monotower is a conical

tu&e* stretching all the way to the surface' A&ove the surface* the monotower ends with a flange*and here the diameter of the monotower corresponds to the diameter of the installed tur&ine

tower' %he transition is made with nuts and &olts'

A suction &uc!et monotower is welded from steel plates' %he thic!ness varies from 20 to 35

millimeter'

Installation

%he !ey element of this structure is suction' %he support structure is planted in the soil using a

vacuum* and doing this* it saves time in installation' 4irtually any vessel can operate the suction

process* and the support structure is not harmed &y a hammer li!e piles'

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%he s!irt is fitted with noles flushing the soil when the support structure moves downwards'

%he nole flushing assists the suction and ena&les steering of the support structures as it goes

into the soil'

%he support structure is mounted at a speed of 6 meters per hour* and with help from the

noles* a tolerance of 0'/ degree inclination out of vertical can &e reached'

lic! here to view large image

The s*tion '*ket monotower *onsists of tower (shaft), &i" ('ra*ings) an" skirt. The &i" an" skirt *onstittes

the '*ket. The win" tr'ine tower is monte" "ire*t&y on the monotower.

%he suction &uc!et monotower can easily &e removed again' 7ressure is applied* and the entire

support structure lifts from the soil'

$f a large roc! is encountered in the installation process* the installer also shifts from vacuum to

pressure* thus lifting the support structure and moving it slightly for a new run'

8owever* the suction and noles approach limits the suction &uc!et monotower to certain types

of sea&ed' %he installation can only &e done in residual soil* where no roc!s occur'

Performs like gravity ases

+hen installed* the &uc!et acts li!e a gravity-&ased foundation' alculations and tests show thatthe soil within the s!irts is trapped and &ehaves li!e a mass &loc!'

$n )rederi!shavn* the &uc!et monotower is mounted with a 9 M+ 4estas 40 wind tur&ine' $t

has &een standing since 6006* and has not tilted more than allowed &y the tur&ine manufacturer'