Windfarm Service Boats

Ad Hoc Marine Designs have been engaged within the Windfarm industry for several years in varying roles from designing windfarm boats through to general advice and consultancy of feasibility projects. Both John and Nigel sit on the MCA’s High Speed Advisory Group which deals with the issues of the high speed industry from a designers, and legislators perceptive and the RINA HSV committee. John also sits on Lloyds Register Technical committee, serving a similar role as the HSCAG.

Being on these committees and working close with Flag and Class, we have developed a better understanding of the needs of this growing industry. The formulation of new rules and regulations have enabled us to ascertain the direction the industry may take and can therefore advise on the latest developments.

Having designed several Windfarm boats and also unique methods of transfer of windfarm technicians from the vessel to the turbine we have established very good relationships with several operators of these boats as well as the problems being encountered on a daily basis. This in-depth knowledge provides us with a very clear picture of what is required, and as such, are able to tailor designs and technical advice with greater satisfaction to our clients.

Windfarm Service Vessels

Whatever claims are made by the builders/operators for the seakeeping of the current range of catamarans for wind farm servicing there is little doubt that these small craft 15m to 24 m long have limitations when it comes to meeting head seas in particular. Speeds of 25 knots are mentioned. Significant wave heights of 2m are also mentioned. But the reality is that the two numbers don’t go together. A considerable reduction of speed is enforced by the violent motion in even 1m seas. This is a problem that has plagued the researchers and designers of small fast craft for over a century- that of combining speed and seakeeping. This situation is compounded in the UK for operators of WFSV by the Load Line regulations and MCA invoking the HSC Code vessels over 20knots; see below 'Current Scenario' for more details.

Monohulls, deep vees, catamarans, trimarans, they have all been tried in the wind farm market. SWATH craft are also on the agenda. But they are perceived by the market to be slow and very expensive. But Nigel Warren and John Kecsmar of Ad Hoc Marine Designs have been involved in SWATH designs for 30 years including "Patria" now "Sunflower 22" running from Busan in South Korea, still the fastest commercial SWATH in the world at 31 knots. Other SWATHs have been the Passenger Transfer Craft used by the MOD in Plymouth UK and the Lockheed Martin SLICE crew boats delivered in 2006.

It is this knowledge that has prompted them to design a SWATH called FastSwath especially for wind farm use that can really combine those magic figures of 25 knots and 2m significant wave height so the two figures can work at the same time, without the requirement to slow down. Additionally, the design is under the 24m Loadline restriction which over comes many regulatory hurdles. A typical General Arrangement layout of the 24m Fast Swath is shown and a brief specification & details attached. These of course can be altered to suit your own requirements.

This particular 24m FastSwath is unique to the Windfarm Market. It is suitable for the heavy workboat and crew boat duties that these vessels are required to perform whilst at the same time being able to maintain a year round operability. A SWATH not only has significantly lower motions, but more importantly it can maintain service speeds in ever increasing significant wave height. Ad Hoc currently have a 17m version for a UK Wind Farm service provider that is being built and also a 15m Workboat in Asia.

In the Gallery is also shown more variations of the WFSV Swaths designed by Ad Hoc Marine Designs. These range from 15m up to 50m and speeds from 12 knots up to 30 knots. More details upon request.

We have given a brief description of some of the problems that currently face this new industry. This has been printed in the August 2010 edition of Work Boat World.

An excerpt from the WBW article is given below:

Current scenario

Offshore wind farms are sprouting up rapidly in European waters around the shores of the UK, Denmark, Germany and several other countries. In order to assist with the construction and maintenance of these turbines a large number of small vessels are in operation mainly to take technicians and small items of equipment out to the site. Time is money so the vessel’s speed is of the essence. The industry is developing fast but the ideal type of boat has not yet been developed. Reliability is important, not just in terms of machinery but also in the ability of the boats to get the technicians in a degree of comfort out to the turbines and then transfer them to each wind tower safely, and back again. The ability to cope with various seastates is therefore of prime importance. Currently all shapes and sizes of craft are in service, monohulls, catamarans and trimarans, all diesel powered some with jet propulsion and some with propellers, fixed pitch and controllable pitch.

The lengths vary from about 10m to about 20m, and they carry up to 12 passengers and can do around 20 to 28knots generally. Predictions show that there will be thousands of these vessels built in the next few years.

The wind farm sites are gradually spreading further from shore into deeper and rougher waters and there is a demand for more speed, greater ability to operate and transfer in rougher water and also to carry more passengers. This inevitably means that the boats will get bigger and more sophisticated. For instance the current method of transfer of the technicians onto the ladder provided by most wind tower providers is for the boat to nose up against two vertical bars and apply up to full power to maintain position. The technician then steps off the bow onto the recessed vertical ladder and climbs a few metres up to the tower.

Naturally these craft have to be certified to operate. In the UK the code of safety usually applied is the Small Commercial Vessel code of safety. This is a sensible well developed code that allows up to 24m Loadline length, 12 passengers or 1 tonne of cargo. It allows practical and inexpensive construction and operation and categorises operation in 6 different distances from a safe haven from 3 miles to unrestricted. Speed is not an issue. There is no stipulated seastate in which the boat can operate- it’s up to the master. There is no legal requirement for the design or build to be approved by a Classification Society.

The Problem

Energy providers are becoming more demanding as their scope increase. Classification is being asked for, bigger seastates, more passengers and less passage time etc.

Energy providers who construct and operate these windfarms contract out their requirements to windfarm boat operators, in parcels. Anywhere. So these boats may have to operate out from different ports in Europe not just the UK at any time. Other countries flags have different technical requirements and modifications may have to be made (if possible) before a boat can operate in (say) German waters. There is no uniform code.

This situation is hard enough when the boats are less than the SOLAS 24m rule, and carry less than 12 passengers- also a SOLAS criteria. And if the speed is more than 20 knots this can be an issue invoking the SOLAS HSC Code.

Current policy in the UK is that if a boat carries more than 12 passengers and it is faster than the speed criterion stated in the HSC code, then it must meet the HSC Code. The speed criterion is related solely to displacement and even a 100 tonne boat will be HSC if it can do more than 15 knots. The HSC Code was principally devised for fast passenger/car ferries carrying hundreds of fare paying passengers whether disabled, elderly or a child (not counting babies under one year old). See figure for principal differences between the SCV and HSC code.

So there are three problems:-

1. Under 24m/12 passengers. Lack of uniformity in the EU flag states.
2. A bigger problem is if the EU flag state demands Classification.
3. An even bigger problem is if the craft is more than 24m/12 passenger (‘passengers’ in SOLAS definition of word) and over 20knots.