EU Projects / OPTI-PILE

Project description
The OPTI-PILE project has been sponsored by the European Commission in the framework of the Fifth Research and Technological Development Framework Programme (contract NNE5/2001/245) and was executed between early 2002 and February 2004.

The objective of OPTI-PILE was to develop and engineer cost-effective mono-pile foundations for offshore wind turbines placed in deep water (> 20 meter) and with conditions characteristic for the North Sea and other Atlantic continental shelves. Since foundation costs amount to more than 20% of the total investment costs, optimisation of foundations is clearly crucial to the economic feasibility of deep water offshore wind farms.
In order to carry out detailed design optimisations for mono-pile foundations in deep water it is necessary to have detailed information on soil conditions, soil characteristics, scour behaviour and effective scour protection methods for conditions characteristic for the deeper parts of the North Sea.

The OPTI-PILE project was part of the engineering of the 120 MW offshore wind farm Q7-WP located 24 km off the Dutch coast at IJmuiden in water with a depth varying from 20 - 25 meters. Offshore construction of the offshore wind farm Q7‑WP commenced in 2007. The results of OPTI-PILE can be and have been generalised to other similar locations. Thus OPTI-PILE is of relevance to many offshore areas with similar characteristics. Not only in other parts of the North Sea, but also in major parts of the Atlantic, the Baltic Sea and even in some parts of the Mediterranean Sea.

Partners in the OPTI-PILE project were E-Connection Project (project co-ordinator), Vestas - Wind Systems (DK) and Germanischer Lloyd Windenergie (D).

Results
OPTI-PILE was part of the initial and detailed design of the mono-pile foundation for the Vestas V80 - 2 MW offshore wind turbine as used in offshore wind farm Q7-WP. The initial design, based on interpolated soil data, was finalised in 2002.
As part of the OPTI-PILE project a study was carried out to find ways to extent the economic lifetime of mono-pile foundations by applying actual strain monitoring on the piles during operation. One of the benefits of load monitoring is an extension of the economic life-time (and associated additional revenues) of the monitored wind farm. Another is the potential reduction of safety factors (and associated savings on investment costs) for future wind farms. The study showed that the additional investment in load monitoring can be recovered within only two months of additional operation. Thus load monitoring is a feasible option.

The mid term results of OPTI-PILE were presented at OWEMES 2003 in Madrid. The final results of the OPTI‑PILE project were presented on January 29, 2004, at a special workshop at Rheden, The Netherlands.

EU Projects | SAFESHIP

SAFESHIP: reduction of ship collision risks for offshore wind farms

Project description
The SAFESHIP project has been sponsored by the European Commission in the framework of the Fifth Research and Technological Development Framework Programme (contract NNE5/2001/521) and was executed between early 2003 and February 2005.

The objective of the SAFESHIP project was to (further) reduce the risk of ship collisions with offshore wind farms  through the development of damage reduction methods and technologies and the development of risk assessment methodologies. Feasibility studies of these damage reduction methods and technologies resulted in a ranking. The more promising methods and technologies have been studied in greater detail. Furthermore probabilistic models for the risk assessment of ship collisions with offshore wind farms have been developed.

Partners in SAFESHIP were E‑Connection Project (project co-ordinator), Vestas ‑ Wind Systems, the Technical University of Denmark - Dept. of Maritime Engineering, the Technical University Delft - Dept. of Marine Technology, Germanischer Lloyd, Germanischer Lloyd WindEnergie and the Maritime Research Institute Netherlands (MARIN).

Scope of the project
SAFESHIP deals with the possibility of maritime accidents related with an offshore wind farm. A collision of a ship with an offshore wind farm will have impact on the offshore wind farm (damages, injuries, loss of energy production), on the colliding ship and on the environment (spills).
Although the chance of ship collisions with offshore wind farms is very small, the consequences can be huge. For instance a collision with an offshore high voltage substation could ultimately result in the loss of millions of euros by loss of investment, loss of energy sales and penalties for non compliance with the PPA. Therefore risk management is an important issue. Costs associated with ship collision risks include the costs of safety measures and of insurance premiums too.
SAFESHIP specifically deals with the reduction of ecological risks related to spills of oil or eco-toxic chemicals  following the collision of a ship with an offshore wind farm. Literature on environmental aspects of offshore wind energy does not, or only briefly, mention these risks and focuses on the impact on operations. Nowadays however this issue is a critical one for investors and operators of offshore wind farms and is addressed in depth in the Environmental Impact Assessment studies. Examples thereof are the 160 MW wind farm at Horns Rev (Denmark), the 100 MW Near Shore Windpark at Egmond aan Zee (the Netherlands) and the 120 MW Windpark Q7-WP in block Q7 of The Netherlands Exclusive Economic Zone. Specifically for the Windpark Q7-WP extensive studies have been made on ship traffic statistics, ship collision scenarios and probabilities and spill and pollution scenarios. Results strongly depend on the one hand on local conditions and on the other hand on the assumptions and the level of sophistication of the models used. Results indicate that collision of tankers with individual wind turbines is not likely to cause large spills, because the wind turbine will collapse without any damage to the tanker. The effects resulting from the collision of a tanker with the high voltage substation are much greater.

Risk assessment models
The phenomenon of ship collisions with offshore wind farms is more or less comparable to other ship collision issues, such as ship-ship collisions, collisions with offshore oil & gas platforms, or collisions with large structures (e.g. the Oresund Link). Thus the know-how and models of these collisions can be used here too. The few currently available studies on the risk of ship collisions with offshore wind farms are based on these models.
Notwithstanding the wide use of probabilistic models for ship collisions, a number of elements should be improved or developed in order to make such models more suitable for analysing risks of ship collision with offshore wind farms.
The risk analysis on collisions of ships with wind farms is based on two aspects. The first is the collision frequency. A model has been developed that includes the major technical and environmental issues to close possible gaps of existing methods. The second aspect of the risk analysis are the consequences of such accidents. Up till now only highly sophisticated but expensive methods like non-linear finite-element analysis or model tests were available to evaluate the damage to ships or to wind turbine structures. In order to avoid the high costs of these tests, new more simplified methods were developed. These reduce the cost of assessing collision damages significantly. The results of these new methods can be easily used in a quantitative risk assessment.
SAFESHIP focused on developing simplified calculation methods for the structural damages and for the energy absorption following a collision impact. The methods cover the damages to both the wind turbine and the ship. With respect to safety aspects the methods include consequences like fire and explosion as well as the pollution due to spills of cargo or fuel. Furthermore the collapse behaviour of wind turbines has been investigated to assess the risk for sailors due to falling objects.

Risk reducing technologies and methods
SAFESHIP identified possible cost-effective risk (and damage) reducing technologies and methods. The focus was on technologies and methods that either reduce the probability of collisions or reduce the collision damage. As part of the SAFESHIP project feasibility studies have been executed and conceptual designs have been made for a range of methods and technologies. These include:

* Navigational and traffic management measures, using classical techniques as marking lights, painting and buoys, but also more advanced techniques using ICT and advanced radar technology for early warning and decision support.

* Design of wind turbine and high voltage substation to reduce the damage to ship and wind farm. Damage reduction measures include classic fendering techniques, based on the existing expertise of pier, ship, tug and buoy fendering and specially developed for offshore wind farm applications. Damage reduction solutions for offshore wind farms differ from classic applications: On the one hand one wishes to absorb without damage the impact of small vessels and on the other hand one requires a quick and total collapse of the mono-pile (and wind turbine) at or below the sea-bottom when the colliding ship is a larger oil or chemical tanker to avoid damage to the tanker.

The economic and technical aspects of the feasibility have been evaluated. The main result is a catalogue of measures, ranked according to economic feasibility.

SAFESHIP commenced in February 2003. Mid term results were presented on March 12, 2004 at a special workshop at Bunnik, the Netherlands. The final results were presented on January 21, 2005, at a workshop in Wageningen, The Netherlands.