More and more wind farms are now being situated offshore, where winds are stronger and the turbines present less of an issue in terms of visual interference with surrounding landscape. Investors require guidance in the location of their installation, this is where DNV are the leaders.
Making offshore wind turbines a breeze
Offshore wind farms are large investments and represent a higher risk than land based wind farms. Managing this increased risk is therefore essential to achieve business success. To protect these investments, owners, investors, and insurance companies are increasingly looking for an experienced partner to verify that the wind farms will perform successfully through their intended lifetime. As a result, they request that the wind farms they are investing in are subjected to project certification. As a consequence, DNV has developed and is acknowledged as the leading provider of an offshore project certification service that covers all the critical phases of an offshore wind farm project.
A project certificate proves that a wind farm project has been measured up against a standard and found compliant. Issued by a third-party certification body, the certificate lets all parties involved know they can trust that a wind farm project has been measured up against the industry best-practice. By subjecting a wind farm project to certification, the owner can demonstrate awareness of the increased risk involved in moving offshore and willingness to deal with it.
Step-by-step approach
The core of the project certification system consists of six phases each representing a period of time right from verification of the design basis to the in-service inspections. The DNV project certification is based on a step-by–step approach that minimises the total project risk through the following key steps:
- Phase I – Design basis including external conditions
- Phase II – Detailed design
- Phase III – Manufacturing
- Phase IV – Installation
- Phase V - Commissioning
- Phase VI – In service.
In addition to these services DNV also provides activities in the Phase 0 – Feasibility review stage. The Phase 0 – Feasibility review can consist of one or more of the following services verification of conceptual design, verification of site conditions through measurement programmes, investigation into wind resource/energy yield, EIA verification, and the review of permits and grid availability
Phases I – II
In general, phases I to II covers the steps for achieving final design verification, which include site specific approval of the integrated structural systems consisting of wind turbine, foundation, and soil as well as site specific environmental conditions. This verification will be conducted according to DNV offshore standard DNV-OS-J101 “Design of Offshore Wind Turbine Structures, October 2007", or similar standards if requested by the client. In addition to a documentation review of design in Phases I – II, independent analyses may be carried out for critical details. For that purpose DNV has access to several commercial Finite Element program systems and state-of-the art aeroelastic codes. Structural design verification can also cover wind turbine foundations and other structures, e.g. offshore transformer stations.
Phase III – V
Phases III – V involve all the follow-up verification and on site inspections in connection with the implementation of the project. This includes manufacturing survey of support structures, substation and wind turbines and commissioning of these.
Phase VI
The in-service phase implies an activity, in which the wind turbine, support structure, substation, J-tubes and cables are regularly surveyed by DNV during their entire operational life until they are scrapped. A system of periodical surveys by DNV will be used in order to verify that the required standard is observed and maintained.
DNV project certificate
Each phase will be completed with a statement of compliance and after completion of phases I through V the DNV project certificate will be obtained. The project certificate is valid at the time of commissioning of the offshore wind farm. For the in-service phase, the project certificate is validated based on the results of annual surveys and inspections.
Accreditation
DNV Wind Energy has been accredited by Dutch Accreditation Council RvA to provide project certification services according to the IEC, the Danish and the DNV scheme covering both onshore and offshore wind farm projects.