Offshore Wind Recommended Practices
In October 2009, the American Wind Energy Association (AWEA), in conjunction with the National Renewable Energy Laboratory (NREL), initiated an effort to develop a set of recommended practices for assessing offshore wind energy wind turbines in the United States and to make recommendations on the local, national, and international standards and guidelines that are being used to determine their applicability in the context of unique U.S. conditions such as hurricanes, safety, and supply chain issues. The effort is divided into three major areas that are relevant to the Bureau of Ocean Energy Management, Regulation, and Enforcement (BOEMRE) project application and approval process. These areas include structural reliability, manufacturing, qualification testing, installation, and construction; safety of equipment; operation and inspection; and decommissioning.
Known as the Large Turbine Compliance Guidelines initiative, AWEA has enlisted expert stakeholders from the offshore industry community to develop a consensus set of good practices in the use of standards for planning, designing, constructing, and operating offshore wind energy projects in U.S. waters. The group has prioritized its recommendations by considering international standards first, followed by national standards (e.g. American Petroleum Institute), classification society standards (e.g. DNV, GL, ABS), and lastly, commercial standards and guidelines.
The AWEA recommended practices will apply to all bottom-fixed structures installed on the outer continental shelf (OCS) or in near-shore locations (e.g. state waters) but will not necessarily be sufficient to ensure the structural integrity of floating offshore wind turbines.
The AWEA standard development committee for offshore is divided into three subgroups, which will deliver a final guideline by Spring 2012.
The three subgroups are:
Group 1, Structural Integrity: This group is addressing design issues relating to structural reliability of offshore wind turbines. Many wind turbines that will be installed on the Outer Continental Shelf of the U.S. will have already been designed and type-certified to the International Electrical Code (IEC) design classes (e.g. IEC 61400-01). The work of this group establishes the appropriate interfaces between the existing IEC standards and other standards governing the structural reliability of the integrated wind turbine/substructure system. The group will recommend standards and practices that provide a methodology for establishing the sound design of turbines in U.S. coastal regions, taking into account local metocean and soil conditions.
Group 2, Fabrication, Construction, Installation, and Qualification Testing: This group is developing AWEA recommended practices for the safe and orderly deployment of offshore wind turbines during the construction and installation phases. Manufacturing issues unique to U.S. installation of furore offshore wind turbines are being addressed, as are issues relating to the establishment of adequate offshore infrastructure, such as vessels. This group will identify applicable standards from other industries and adapt them to cover these activities. Qualification testing will be treated as an overarching activity that may be applied to any project phase.
Group 3, Operation, Maintenance, and Decommissioning: This group is developing AWEA recommended practices for operation and inspection. The recommendations are not likely to include extensive turbine component inspection; owner-investor wind farm maintenance systems are generally more comprehensive than periodic inspections that could be carried out by BOEMRE or other federal agencies, and the consequence of failure in a secondary component are generally limited to economic risk to the wind farm itself. Issues involve in-service structural inspection of the tower and substructure or below the waterline are expected to be important. 20-year design life of the turbine and substructure necessitate long term thinking about to decommissioning in which the foundation and substructure is removed and disposed of when it is no longer serviceable.
The three groups will merge their documents and submit a single integrated document for peer review in the Fall 2011. External reviews will be transparent such that the goal of industry wide acceptance is achieved.