OFFSHORE ACCOMMODATION
Whereas mistakes like these have been very expensive to fix, when it comes to personnel safety, short cuts are not an option.
POSSIBLE WAYS FORWARD There are a variety of proposed schemes being developed for safely housing and ferrying personnel to, from and within the offshore wind farms. Mother and daughter craft are proposed similar to the navy’s approach to deploying their amphibious landing craft. The Seawind concept below is an example of such an arrangement.
Through the Safety Case risk studies, the helicopter travel to and from the platforms has been shown to be the largest contributing factor to fatalities offshore so these helicopter movements are minimised by careful planning of rotas and routines of the personnel working offshore.
With the large number of farshore turbines planned, the maintenance routines cannot be supported directly by small craft operating directly from onshore due to the strict safety requirements of Maritime and Coastguard Agency (MCA). Similarly for safety reasons, routine access by helicopter is neither practical nor desirable.
Permanently moored vessels similar to a flat barge are another. The concept shown below developed by SEATEL would be designed to be moored indefinitely up to 70 miles offshore, secured using a single point mooring system and a fixed anchor spread specifically designed for each location.
Oil and Gas experience however would suggest that spread moored vessels are not the way to go for the UK waters. Spread moored Floating Production Units (FPUs) are only used in very benign waters such as offshore West Africa. For
the UKCS, weather vaning FPSOs are now deployed throughout although there are two examples of spread moored cylindrical hulled FPSOs but these are not flat barge based designs.
Flotels have been used in the oil and gas industry for many years and these are normally based on a semi-submersible hull moored to the seabed similar to a drilling rig.
Operational experience of FPSOs shows that helicopter movements are regularly hampered by the motions of the vessels in even moderate sea conditions, therefore barge based concepts would most likely not provide the operational conditions required for all year round maintenance activities.
FIXED OFFSHORE ACCOMMODATION PLATFORMS
The most obvious and well proven solution is a permanent accommodation module located within the wind farm. Separate accommodation platforms do provide all of the requirements for personnel safety and comfort.
Accommodation areas can also be incorporated into the very large HVDC platforms being proposed provided that safe barriers can be incorporated personnel protection.
A CONCEPT FOR A HVDC PLATFORM DONG Energy is experienced in oil and gas and are now well established in the offshore wind industry. For their Horns Rev II wind farm located 19 miles offshore in the Danish sector, DONG have installed a permanent Accommodation platform located alongside the Transformer Substation.
LESSONS LEARNED
Lessons can be learned from the oil and gas industry, unfortunately it is seen as an expensive industry and has been largely ignored by some sectors of the offshore wind industry leading to costly mistakes such as the grouted connections used on some of the monopile foundations.
This is the first permanent accommodation module to be installed in an offshore wind farm and sets the scene for others to follow. The maintenance crew are housed inside a standard 24 man accommodation module is designed and built to offshore oil and gas standards. The crew fly to and from onshore by helicopter allowing safe maintenance conducted 365 days a year.
www.windenergynetwork.co.uk
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