Ten thousand offshore wind turbines are expected to be installed in European offshore waters until 2020. What requirements must wind[ds_preview] turbine installation ships (WTIS) fulfil and what regulations apply? Offshore engineering and wind farm development was the topic of the GL Exchange Forum in cooperation with Samsung Heavy Industries, Beluga Hochtief Offshore, Huisman, and BLM Jack up Systems in June in Hamburg.
Wind energy is one of the key renewable energy sources that will make a significant contribution towards the goals of clean energy around the world. The wind energy industry is in a period of significant growth. New capacity is installed predominantly offshore rather than onshore – at least in Europe. Many market players are in the field and many different design concepts for offshore wind parks exist. The main driver is a political one: By 2020 the EU wants to cover 20 % of its primary energy consumption with renewable sources. »Therefore, there is a large potential for market growth«, concluded Teena Tillessen, GL’s deputy head of department special projects in her analysis of the market situation.
This is underlined by current numbers from the European Wind Energy Association (EWEA). In 2010, the total installed offshore capacity reached 3,000 MW. This meets 0.3 % of the total EU electricity demand. For the year 2030, 150,000 MW installed offshore capacity are projected, which will meet between 13 and 17 % of total EU electricity demand.
Today, predominantly in the so-called 20:20 envelope of 20 m water depth and 20 km away from the shore, future wind parks will need to meet more challenging environmental demands. Projects in Europe are planned for distance of up to 60 km from the shore, placed in water depths of up to 60 m. Moreover, concepts are being developed for projects in Northern Europe with a distance of up to 140 km from shore while wind farm developers for Southern Europe are thinking of water depths of up to 300 m. Overall, wind parks will become larger: A single wind farm consisted in 2002 of about 20 wind turbines and by 2020 may be as large as 1,000 individual turbines.
In respect to suitable installation vessels there seems to be a danger of insufficient number which could constrain offshore wind development in the coming years. It is planned to install some 800 foundations and wind turbines p.a. until 2020, according to the EWEA. This requires new installation vessels capable of handling the next generation of offshore turbines of between 3–5 MW and ever bigger foundation types. With increasing turbine power also the weight of nacelle and tower grow, so that installation vessels specially designed to handle bigger turbines will come into operation. According to Renewable UK, the demand may be as high as 50 special vessels for operation and maintenance support, cable laying, wind turbine installation and crew transport. For Europe, a need of 15 to 30 wind turbine installation ships is projected.
Design
What is the best design to meet the requirements, is the important question. The ship design needs to take into account the expected turbine size, the water depth, distance from the shore and the given time window for installation. The ship owner and operator have to decide if the ship should be self propelled, with jacking capability, sailing speed, size of crane and lifting appliances, number of compartments and dynamic positioning.
GL has identified three generations of wind turbine installation ships: The combined operation of crane and a working barge, which together supply high lifting capacity, high deck load capacity and a large working deck is considered as the first generation. This is used quite often in areas close to the shore, or in case suitable vessels of generation II and III are not available on the market. Generation II combines these capabilities in a self-elevating, non self-propelled barge which, in addition, to generation I provides also a helicopter deck and a large accommodation area. The Jack-up barge »Thor« with a 70 x 40 m working deck and a crane capacity of 500 t is one example for this vessel type. The ship is classed by GL.
The third generation, which is mainly used in areas further from shore, provides all of the above and is an independent self-propelled vessel. This reduces the time needed for installation significantly, since the time needed for transferring the foundations, towers, turbines and blades from a transportation barge to the installation barge can be saved. In addition, this makes the operation much saver as well.
One common advantage of the latest generation vessels (generation III) is that dynamic positioning of level 2 (»DP2«) has become the quasi standard. This leads to the big advantage, that these vessels do not require anchors to be run while manoeuvring, allowing to operate significantly quicker. Dynamic Positioning (DP) is a computer-controlled system that automatically maintains a vessel‘s position and heading. No moorings, no anchor handling is needed anymore. Instead, own propellers and thrusters are being used while sensors for environmental forces and motion combined with a GPS position reference system control the positioning of the vessel.
To date, GL’s Maritime business segment is already involved in more than 18 wind installation and maintenance newbuilding projects. Overall the GL Group offers combined forces for offshore renewable projects: GL’s maritime services does Technical Assessments, Vessel Classification and Measurements. The renewable energy business segment GL Garrad Hassan takes care of wind farm planning & certification, turbine certification and electrical infrastructure assessments. And GL Noble Denton supports its customers with ship design, project management services, foundation engineering and marine warranty survey. The combined experience from the renewable sector, offshore installations and maritime operations within GL Group provides the groundwork for a comprehensive service portfolio and offers the competence to assist in any step of the project across all industries.
Key Success Factors for WTIS are reliability, facilitating the biggest possible operating time window and largest possible flexibility for future requirement profiles.
Rules and regulations
From a rules perspective an important question needs to be answered: What exactly is a wind turbine installation ship? Is it a ship, a jackup, a heavy lifter or a passenger vessel – which rules do apply? Main characteristics of all of these different ship types are combined in such units.
From a regulatory point of view this is a very complex situation. Unlike with other new technical developments, where suitable rules and regulations have to be invented to provide a reasonable safety standard, for WTIS it is not a question of developing new rules sets. To the contrary, there are many rules books to follow, each of them traditionally developed for one of these options. So these hybrid concepts have to fulfil various, sometimes contradictory rules and regulations simultaneously. Due to the various projects that GL is involved with, comprehensive experience has been gained in guiding designers, owners and shipyards through all these requirements. This applies to the own rules for classification (e.g. seagoing vessels vs. offshore technology), but also to statutory requirements, which have been discussed with various flag states. It has been proven to be very beneficiary for all involved parties, to agree on the same understanding for applicable IMO Codes and Conventions at an early stage of a project!
Teena Tillessen
