Inward Battered Guide Structure,

the “Twisted Jacket”

an innovative offshore

foundation reducing cost and risk

compared to traditional offshore foundations

a proven concept

The Keystone Inward Battered Guide Structure (IBGS)

is a top 4 finalist in the Carbon Trust’s

Offshore Wind Accelerator (OWA)

foundation competition.

The patented IBGS foundation was

used by SMart Wind, the joint venture

between Mainstream Renewable

Power and Siemens Project Ventures,

for the installation of the first

meteorlogical mast in the Crown

Estate Round 3 Waters.

The “Twisted Jacket” foundation aims

to significantly reduce foundation

CAPEX cost.

The initial IBGS used to support

an oil and gas platform in the Gulf

of Mexico withstood Hurricane

Katrina, a 400-year return

period metocean condition,

with no damage.

Keystone IBGS or “Twisted Jacket”during transport to the

4GW Hornsea Zone

COSTApproximately 20% less expensive than traditional windturbine generator (WTG) jackets independently verified by contractor estimates and confirmed by fabrication experiencegained through the Hornsea MET Mast Foundation demonstration project. The IBGS becomes cost competitivewith monopiles at approximately 30m when supporting a 5MWor greater WTG. This depth becomes significantly shallower in US waters since large diameter monopiles require largerinstallation equipment currently only found in Europe.

FABRICATIONThe IBGS has fewer nodes and components comparedto a traditional jacket making it easier to assemble. Fewerwelds are required since there are fewer braces. The IBGSlends itself to serial production. Weight redistribution fromjacket steel to less expensive pile and caisson steel greatlyreduces the fabrication cost. The IBGS footprint in verticalposition takes up less space than a traditional jacket for stor-age at staging site. The IBGS is safer and easier to man-ufacture than traditional jackets since it is fabricated horizon-tally to the ground, not vertically. The IBGS does not require castings or jacket to pile pins that traditional jackets do.

TRANSPORTATIONThe IBGS is more compact (shorter and smaller foot-print) allowing for more structures to be transported per tripto site. The triangular footprint of the IBGS is easier to arrangethan the square footprint of a traditional jacket. Independent installation contractors have shown that 5 IBGS comparedto only 3 traditional jackets can fit onto the sameinstallation vessel reducing transportation costs.

INSTALLATIONNo offshore welding and no underwater work is needed, whichgreatly reduces HSE, commercial and schedulerisks. It is possible to use less expensive vessels to install the vertical caissons and to perform grouting operations. The cais-son, guide structure and piles can be installed withoutrepositioning the installation vessel. In the US Market,the equipment spread costs are less for an IBGS versus a monopile. The IBGS needs smaller hydraulic or vibratory hammers than those used for monopiles. Additionally, smallerinstallation vessels can be used since the IBGS is lighterthan monopiles.

MONITORINGThe Hornsea met mast foundation is instrumented abovewater, underwater and below the seafloor to gain maximum data on the performance of the foundation.

DECOMMISSIONINGPiles and caisson are all accessible from the surface and canbe severed below the seafloor using traditional techniques.The entire IBGS with piles and caisson sections can be liftedand placed on a cargo vessel with the same lift vessel used toinstall the foundation. Based on current charter rates and scrap metal prices, the foundation decommissioning iscost neutral or negative. This reflects significant savings compared with monopiles and traditional jackets with pre-installed piles.

CERTIFICATIONThe composite transition has been derisked through pre-verification by DNV for wind turbine loads and DNV has stated that the foundation can be certified for commercialwind farm applications. The independent TechnicalDelivery Consultant (TDC) employed by the Carbon Trust for the OWA program has reported to the OWA Steering Com-mittee that the foundation is suitable for commercial applica-tions. DNV has independently verified the composite steel tube grouted node design and pile splice design for the Hornsea met mast foundation, the first met mast to beinstalled in a UK Round 3 Area.

ENVIRONMENTThe driving hammer used for the IBGS is smaller than a ham-mer used to drive a monopile and for pre- or post-installed piles for a traditional jacket. Thus, the pile driving noise is less for the IBGS which reduces the affect on aquatic mam-mals in the area. In addition, the IBGS can also be installed with a vibratory hammer or by drilling techniques to virtually eliminate driving noise. The IBGS is well-suited for the appli-cation of AdBm Technologies’ SoundShield System, a passive, silent and highly-effective noise abatement system based on years of research in bubble resonance phenomena.

PROVEN CONCEPTTwo IBGS have been used to support oil and gas platforms in the Gulf of Mexico. The initial foundation withstood Hurricane Katrina, a 400-year return period met-ocean condition with no damage proving the inherent robustness of the foundation. Push-over analysis has shown that the structure has reserve strength ratio (RSR) slightly greater than a typical four-pile jacket. In October 2011, the Hornsea Met Mast foundation was installed in UK Round 3 waters to support a meteorological mast, which proved the installation techniques in North Sea conditions. The prototype foundation is instrumented to monitor structural perform-ance. Initial data will be evaluated and used to enhance per-formance of future foundations.

Keystone IBGS in the direct path of Hurricane KatrinaGulf of Mexico, August 2005

Hornsea Met Mast Foundation

At Keystone, smart engineering design is our strength.Our innovative, patented designs and over 20 years of

offshore engineering experience combined with ourcommitment to excellence provide you with

the best result for your project.

A MULTI-DISCIPLINEDENGINEERING CONSULTING FIRM

• Conceptual / Feasibilty Studies

• Detailed Cost Estimates

• Project Management

• Engineering

- Civil/Structural

- Mechanical

- Process/Chemical

- Electrical

- Instrumentation/Controls

• Design/Drafting

• Programming and Integration

• Procurement

• Construction Management

• Inspection Services

• Fabrication Engineering

• Installation Engineering

• Decommission Planning

Benjamin Foley • General Manager, Offshore Renewables(+1) 504.220.1742 • bfoley@keystoneengr.com • www.keystoneengr.com

U.S. Patent Nos. 7,198,453, 7,134,809 & 6,783,305 and related foreign patents; U.S. pending applications and related foreign applications