PO076

The benefits of an updated international standard for the future design of offshore wind turbines & their support structures

James Manwell 1, Tim Camp2, Niels Jacob Tarp-Johansen3
1University of Massachusetts, Amherst, USA, 2DNV GL, Bristol, UK, 3DONG Energy, Copenhagen, Denmark

Abstract

The International Electrotechnical Commission standard for bottom-fixed offshore wind turbine design (IEC 61400-3) has been significantly updated to reflect advances in offshore wind turbine technology and the increase in offshore wind experience gained by the industry since the standard was first published in 2009.

This presentation will describe the most important updates to the standard and will illustrate the impact of the changes from the designer's perspective. Significant updates include simplifications to the design load case specifications to make the standard simpler to apply, a greater focus on the assessment of site-specific environmental conditions, additional guidance on ice-loading of offshore wind turbines and their support structures and new guidance on extreme loads which result from tropical cyclone events. The standard has also been aligned with the latest updates to the onshore wind turbine design standard IEC 61400-1.

This presentation will be the first public presentation of the new standard to the industry and will be of interest to wind turbine designers, support structure designers and fabricators, certification agencies, project developers and insurers. A key objective of the presentation is that delegates will be confident to use or specify the new standard for future offshore wind turbine and support structure design projects.

Method

A substantial review of the standard was carried out by a team of 40 international experts from industry, academia and certification bodies. Ten meetings of the Maintenance Team were held over a period of four years at which the requirements of the standard were discussed, the work of sub-groups was presented and updates to the final text of the standard were agreed.

The starting point for the work of the Maintenance Team was a set of recommendations from IEC TC88 national committees following review of edition 1 of the IEC 61400-1 standard. Members of the Maintenance Team added their own experiences of using the first edition of the standard and suggestions for improvement. A Committee Draft for Voting was circulated to national committees in 2017.

Results

The Maintenance Team were very conscious of the needs of the designer and sought to make the standard as straight forward to apply as possible. Simplification of the load case specifications to reduce the number of extreme load simulations was one example of this.

As the design of offshore wind turbines and their support structures requires site-specific conditions, greater focus was put on assessment of environmental data.

To increase international applicability of the standard, more guidance was provided on ice loading of wind turbine structures and new guidance added on the prediction of tropical cyclone loading.

Additionally a number of changes were made to the standard to align it more closely to the latest updates to the IEC standard for onshore wind turbine design 61400-1.

Conclusions

Edition 2 of IEC 61400-3 contains significant updates which embody the latest best practices of the offshore wind industry and make the standard easier to apply.

The international composition of the Maintenance Team has led to a standard which will be accepted in new territories for development of offshore wind as well as established territories. Similarly, the broad industry representation within the team led to a standard which turbine OEMs, support structure designers and certification agencies will be confident to apply.

Edition 2 of IEC 61400-3 will be reviewed by national committees in 2017 and it is expected will be published later in the year. A separate technical specification for the design of floating offshore wind turbines is also expected to be issued in 2017.

Objectives

An update to the IEC design standard for offshore wind turbines and their support structures is a significant milestone for the industry. This presentation will be the first public presentation of the new standard to the industry and will be of interest to wind turbine designers, support structure designers and fabricators, certification agencies, project developers and insurers.

The presentation will describe the most important updates to the standard and will illustrate the impact of these from the designer's perspective. Additional guidance that is provided on ice-loading and load effects of tropical cyclones will also be described.

A key objective of the presentation is that delegates will be confident to use or specify the new standard for future offshore wind turbine and support structure design projects.