Cable Installation for Offshore Renewables: The Unique Challenges

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Global Marine Systems Limited has been at the forefront of cable installation for offshore renewables ever since the industry emerged in the early 2000s.

As well as installing cables for Europe’s first commercial wind farm at Horns Rev off the coast of Denmark in 2002, Global Marine laid the cabling for the UK's first commercial wind farm at Kentish Flats in 2005. More recently, Global Marine has been involved in the installation at Thornton Bank 3 off the Belgian coast and Global Tech 1 (working on behalf of Prysmian) in the German North Sea. This year Global Marine will begin offshore cable laying work on the Wikinger installation again on behalf of Prysmian, in the German Baltic Sea.

Demand for greener energy

Given the agreement reached at the 2015 Paris Climate Summit, at which participating nations agreed to keep global warming "to well below 2 degrees C", the demand for renewables such as offshore wind and tidal farms is only likely to increase – both politically and economically. 

A viable energy source

But as well as being environmentally friendly, renewables are now a truly viable alternative to traditional power generation systems such as coal and nuclear. Denmark, for instance, produced nearly half of its electricity from wind farms in 2015, breaking its own world record. The UK’s wind power sector continues to grow too, producing 11% of the nation’s electricity needs last year, and 17% in December alone. Considered one of the best locations in Europe for wind power generation, there remains vast potential for further industry growth in the United Kingdom.

Wave and tidal power generation also present great opportunities, with the potential to produce up to 20% of the UK’s current energy demands. The Cardiff Bay tidal lagoon project in particular has captured imaginations, with claims that the proposed 14-mile seawall could power every home in Wales.

The unique challenges 

But planning and constructing these power generation systems takes long time horizons, extensive skill, technical ability and experience. Laying cables for the offshore renewable sector presents unique challenges. These include working safely and effectively with monopoles positioned in close proximity; dealing with multiple contractors and communicating effectively with the client; carrying out operations in ever-deeper water as wind farms move further offshore; and operating in areas where minefields and unexploded ordnance from World War Two are still present.

However, planning and executing an offshore renewables project does share some similarities with other sectors – such as oil and gas. In all circumstances a bespoke project implementation plan including all critical path items is created, based on the provision of cable route services, including desk top studies, permitting, route surveys, environmental assessment reports and route engineering.

A subsea solution that lasts

Engineering a subsea installation solution that lasts is critical. This is achieved primarily by investing heavily at the planning stage of a project in order to protect against possible future costs – to both owners and insurers. 

Nevertheless, faults occur and cable downtime has a significant financial impact.  It is imperative that repairs are undertaken in a timely manner to avoid long-term disruption to the wind energy extraction.  Physical threats to cables – such as anchor strikes, dragging fishing nets and erosion – are considerably more common than internal faults. One study by the international association of electrical power experts, Cigré, examined offshore interconnectors linking electricity transmission systems for wind farms. It documented 49 reported damages between 1990 and 2005 worldwide; 41 of these were caused by ‘third party’ threats – such as anchor strikes.

According to a European Offshore Grid Infrastructure Study, subsea power cables suffer an average of 0.5 – 2.0 faults per year per 1,000 km of installed subsea cable. 

More cable terminations

The planning stage for any offshore renewable project involves preparing for large numbers of cable terminations – many more, for instance, than an oil and gas project requires. Multiple cable terminations require detailed planning, demand more resources and take longer to install and engineer.

During the Horns Rev 1 installation, Global Marine engineers made 150 landings, each of which involved pulling a cable from the sea bed, through the protective J-tube, and attaching it to the inside of a given turbine. A large number of at-sea personnel transfers and numerous diver operations were required in order to successfully install the cables to schedule. Delays caused by severe weather conditions are anticipated and accounted for at the planning stage.

Key to success

Global Marine’s technical ability, skill and experience is founded on a 165 year legacy in subsea engineering and an involvement in the offshore renewable sector for nearly 2 decades.  As such we understand what is required to deliver a successful offshore renewable cable installation project. In short, it demands an extremely well-planned logistical operation, and smooth execution.

Achieving this requires highly trained, expert personnel, often maintaining a 24 hour operation. It also necessitates cable installation vessels and submersible equipment that can operate in all manner of shallow and deep water locations. 

Here at Global Marine we have both the personnel and the hardware to complete cable installation projects for offshore renewable sites of all sizes – on time and within budget. The recent acquisition of offshore renewables specialist CWind demonstrates Global Marine’s continued commitment to the offshore renewable sector and adds a diverse range of construction and O&M services to its current capabilities.

Discover more about Global Marine’s unrivalled experience in this sector.

Or contact Global Marine today.


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