Lead Session Chair:
Stephan Barth, Managing Director, ForWind - Center for Wind Energy Research, Germany
Laure Grignon (1) F P Hannah Abend (1) Dan Bacon (1)
(1) RES, Kings Langley, United Kingdom
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Presenter's biographyBiographies are supplied directly by presenters at OFFSHORE 2015 and are published here unedited
Dr Laure Grignon is a Chartered Marine Scientist with 5 years’ industry experience in the provision of Metocean criteria and analysis for the development of offshore and maritime energy assets. Since joining RES, she has contributed to the development of the CORE construction weather downtime model and carried out a number of construction logistics studies, in close liaison with the construction project managers during the definition of the installation strategy for offshore wind projects.
Reducing the cost of offshore wind farm construction
Construction represents one of the major cost elements for offshore wind projects. This is exacerbated by weather delays, which can as much as double the installation costs. Reducing cost, mitigating and planning for offshore construction is therefore a key target in order to reduce the levelised cost of energy for offshore wind and to make it a more competitive energy.
While working on projects in the past, RES has developed a software tool that specifically works in the time domain and enables us to estimate construction durations that incorporate the complexities of site conditions and the installation operations. The tool was coupled with in-house installation expertise in order to define the optimum installation strategy for a number of projects. In the current work, we decided to take a broad view of past projects in order to reach conclusions/recommendations that would support the cost reduction across the industry if applied to future projects.
Main body of abstract
First, RES have considered what could be done in order to reduce installation costs while only considering technologies available now. On numerous projects, it is possible to save millions of pounds/euros by upgrading the right piece of equipment. A methodology in order to identify these cost savings will be presented, as well as examples of equipment upgrade recommended for specific packages, whether turbine, foundation or cable installation, and specific weather conditions.
We then looked for operations that could not currently be optimised, but that cause significant installation bottlenecks for more than one installation package. In particular, jacking up and down operations are very limited by the weather, but need to occur at all turbine locations, and for a number of installation packages. They generate a significant amount of downtime at most sites prone to offshore wind sites. We recommend that the industry as a whole should look into innovative solutions, and suggest that new vessel designs need to be considered. The LeanWind project, for example, is considering such issues. Another example is blade installation of turbines, which has significant wind restrictions. We recommend that alternatives to single blade installations be considered as well as improvements to cranes to increase wind limitations for lifts.
It is also noted that there is often a synergy between innovations that allow for quicker operations and that are safer for the crew. Making the operations less hands-on is likely to increase both efficiency and safety.
This work has led to two main recommendations to the industry:
- The overall construction strategy should be well optimized during the project development and until/during construction, using a methodology that retains the specificity/complexity of the site conditions and of the installation sequence. What may seem like a small optimization on paper, may save millions at a given site.
- Focus should be put on designing new vessels that can operate in tougher weather conditions. It is possible to target given thresholds that will save on offshore construction while not being overly costly to build.
This work aims at capturing lessons learnt from installation optimization studies carried out for a number of projects, and to reflect on how the industry can build on this experience to reduce the cost of offshore wind project construction.