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Offshore Wind Journal

Offshore Wind Journal

Late-2019 demo planned for crane/jack-up-free installation concept

Wed 16 May 2018 by David Foxwell

Late-2019 demo planned for crane/jack-up-free installation concept
SENSE uses a simple mechanical interface to install a nacelle and rotor assembly and a specially-designed carriage that lifts it to the top of a tower

The company behind an innovative concept for installing and maintaining wind turbines and reducing the cost of offshore wind energy hopes to demonstrate it by the end of 2019.

The three partners in the project – SENSE Wind, Xodus and Green Marine – are working towards the formal start of a Department for Business, Energy and Industrial Strategy (BEIS)-Energy Entrepreneur-funded demonstrator project next year.

They plan to use the demonstrator to prove the SENSE (self-erecting nacelle and service system) concept at scale before progressing to full-scale demonstration and plan to undertake the design of a prototype system in parallel with the demonstration project.

The SENSE system installs turbines on onshore and offshore projects without large cranes or jack-up vessels. During operation, it can be used in reverse to rapidly exchange complete rotor nacelle assemblies for repair. SENSE Wind said the concept is modular, uses standard, readily available vessels, improves safety and reduces technical and programme risks. It is designed to transport and install a pre-assembled, tested rotor nacelle assembly.

The company completed a 12-month Innovate UK Energy Catalyst study in September 2017 that confirmed the practicality of the turbine installation and maintenance system. The SENSE installation process was modelled using data typical of a standard construction vessel when operating in various sea states.

The Innovate UK study was carried out for SENSE Offshore by a team of leading contractors including GBG, PHG Consulting, Industrial Systems and Control, BVG Associates, Knowtra and James Fisher Marine Services.

It found that SENSE could cut around €125M (US$150M) from the capital expenditure (capex) on a €5.1Bn, 1.2 GW offshore windfarm in waters of in excess of 70 m and save €28.5M a year in operating expenditure (opex). On a shallower, large site where water depths are similar to North Sea windfarms currently being built with jack-ups, SENSE could save €84M in capex and €10M in opex per annum.

In late 2017 SENSE Wind applied for and secured funding through the BEIS Energy Entrepreneur scheme and is currently seeking match funding for the demonstration project. It has also secured the support of a leading manufacturer of offshore wind turbines and UK design and engineering company Houlder.

The demo will be conducted in two phases. In the first, undertaken on land, the ability to lift a nacelle and rotor assembly to the top of a tower will be demonstrated. In the second phase, the companies plan to demonstrate lifting from the deck of a vessel. 

SENSE uses a simple mechanical interface to install a nacelle and rotor and can be used with any turbine design. Automated lifting controls means no human interaction is required during heavy load transfer operations. The system allows rapid turbine installation and maintenance on tall onshore towers and deepwater offshore sites, including floating foundation technology. It eliminates the need for expensive purpose-built vessels or cranes and is suitable for use in any water depth.

For offshore turbines the rotor nacelle assembly, fitted with a special carriage, is transported to site using a standard construction vessel. When close to the tower, the rotor nacelle assembly is transferred to the base of the tower in one rapid operation where the carriage attaches to the tower under automatic control, allowing the transport vessel to move away.

Once the rotor nacelle assembly is attached the carriage, equipped with power supply and automatic controls, it lifts it to the top of the tower and rotates it into position and holds it until secured in place. Once installed, the carriage is retrieved and can be used for the next turbine.

Modelling response showed that SENSE can transfer a 700-tonne rotor nacelle assembly from the vessel to the tower base in sea states typical of the North Sea.

SENSE Offshore managing director Patrick Geraets said “Turbines are getting larger and developers want to exploit deepwater sites. How are these turbines going to be installed? SENSE is an answer – and is faster and less expensive than the alternatives. It is also independent of water depth, with worldwide application and is scalable to the larger turbines coming to market in the next five years.”

Mr Geraets said SENSE is suitable for use on a number of foundations/towers, including different types of jackets, tripods and monopiles. Although the concept does not require the use of a jack-up or a crane, it would require the use of a vessel with dynamic positioning (modelling to date is based on the use of a DP3 vessel) and an active heave-compensation system to reduce motions during installation.

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