Global wind Power 06
Adelaide Sep 21-22
IEA TASK 23
INTERNATIONAL COLLABORATION
Offshore Wind Energy Technology and Deployment
Jørgen Lemming and Flemming Øster
Operating Agent Representative
RISØ National Laboratory
Wind Energy Department
Denmark
Walt Musial and Sandy Butterfield
Operating Agent Representatives
National Renewable Energy Laboratory
National Wind Technology Center
INTRODUCTION
Most of the wind power development thus far has taken place on land-based sites, but future
development will involve an increasing offshore fraction. At the end of 2005, more than 700 MW
has bee installed most of it Denmark and UK waters. In Europe, the amount of space available for
offshore wind turbines is many times larger than onshore. The potential for wind energy is therefore
also considerably greater. As such, plans to expand offshore wind in Europe are well underway,
especially in countries around the North Sea and Baltic Sea areas where shallow water less than a
20-m depth can be found. In the U.S.A there have not yet been any offshore wind installations, but
two significant projects with a combined capacity of nearly 600 MW have already been proposed
and are now in the permitting process.
Existing projects in Europe have proven to be valuable in demonstrating offshore wind energy on a
large scale and have gained important technical experience that will be applied to the generation of
offshore wind turbines. Not all the experience gained has been positive. The costs of offshore
projects have exceeded projections in some cases by underestimating the cost of unanticipated early
repairs and presuming onshore accessibility and reliability statistics will hold true for offshore.
Along with these technical challenges, developers of offshore wind projects are required to analyze
environmental conditions of the specific site. The range of analyses involves submitting permit
applications, conducting baseline data collection, preparing environmental impact assessments, and
conducting pre- and post construction monitoring studies. The methodologies to carry out these
analyses are varied in scope, timeframe, and funding, depending on the national regulatory
requirements and location.
IEA Task 23 – Global Wind Power 06, Adelaide Australia, September 21-22 2006
1
There is a recognized need to compile credible ecological data for a variety of offshore sites and
explore how the existing, site-specific data can be used to facilitate streamlined planning and
approval processes. Environmental and regulatory issues are currently a significant obstacle to
offshore deployment and will increasingly become a more important factor as the technology
matures and greater numbers of deployments are proposed.
Future offshore technology will progress to allow access to deeper waters, which will benefit
coastal nations with less shallow seas such as Ireland, Spain, Italy, and Portugal. Outside the
European Union, China and the United States also have high potential. In the United States,
preliminary estimates of offshore wind resources indicate immense areas of Class 5, 6, and some
Class 7 winds (USDOE wind classes) at distances from 5 nautical miles (nm) offshore to 50 nm
offshore. These estimates indicate that for the U.S., there are over 900 GW of offshore wind
resource in deeper waters (30–900 m) compared to less than 100 GW in shallow water (0–30 m).
Opening these vast windy areas of deep-water ocean for electric power generation will require new
technologies to be developed.
An international collaboration through the International Energy Agency (IEA) is an efficient forum
from which to advance the technical and environmental experiences collected from existing
projects, as well as the research necessary to advance future technology for deep-water wind energy
technology. This free exchange of information and experience will help the offshore wind industry
proliferate.
Description of Task 23
In May 2004, the Executive Committee of the International Energy Agency’s Implementing
Agreement for Co-operation in the Research, Development, and Deployment of Wind Energy
Systems unanimously approved as Annex XXIII (now called Task 23), Offshore Wind Energy
Technology and Deployment. This task is comprised of two subtasks. Subtask 1 is focusing on
critical deployment issues associated with current offshore experience. Subtask 2 is focusing on farterm issues associated with deployment in deeper water. Figure 1 illustrates the general division
between subtasks 1 and 2 within the Task.
Figure 1 – IEA task 23 Technology Subtasks
IEA Task 23 – Global Wind Power 06, Adelaide Australia, September 21-22 2006
2
The stated objectives of this annex are:
To conduct R&D activities of common interest relating to wind turbine facilities operating in offshore environments in order to reduce costs and uncertainties.
To organize several workshops on critical research areas relating to offshore wind deployment issues, including technical research on deeper water structures. The goal of the workshops is to identify R&D gaps in various research areas that are of interest to participating countries, publish proceedings, to identify specific joint research areas needing further investigation and to carry out collaborative work according to agreed work programs within a period of three years.
A detailed list of possible topics for collaboration were identified at a Technical Experts Meeting
held in Denmark in March 2004, and are listed in the task documents as a starting point for
collaboration. The list was prioritized based on the joint interests of the participants and the
appropriateness of the topic for sharing information, and was reduced to four research areas listed
below.
Research Area 1: Ecological Issues and Regulations
Research Area 2: Electric System Integration
Research Area 3: External Conditions, Layouts and Design of Offshore Wind Farms.
Research Area 4: Modeling Needs for Offshore Substructures (including deepwater floating
systems)
Research Areas 1 through 3 are being conducted under Subtask 1. Research Area 4 is being
conducted under Subtask 2 as shown in Figure 2.
Task 23 Operating Agents
Risø and NREL
Subtask 1 (Risø Jørgen Lemming)
Experience with critical deployment issues
Research Area # 1
Ecological Issues and Regulations
TBD
Subtask 2 (NREL Walt Musial)
Technical Research for deeper water
Research Area # 4 Offshore Code Comparison
Collaboration
Sandy Butterfield - USA
Research Area # 2
Electrical System Integration
Goran Strbac - UK
Research Area # 3
External Conditions, Layouts and
Design of Offshore Wind Farms
Flemming Øster - DK
Figure 2 – Task Organizational Flow Chart
Participation
So far 8 countries have joined Task 23. Commitment letters have been received from all eight.
It is still possible for other countries and organizations to join the annex. However participation in
some of the subtask issues may now be a problem since the work program has been defined.
IEA Task 23 – Global Wind Power 06, Adelaide Australia, September 21-22 2006
3
Country
United States
Membership Status/
Contracting Party
Committed/
US Department of Energy
Denmark
Committed/
Danish Energy Authority
UK
Committed/
Department of Trade and
Industry
Committed/
Enova SF – Pending
Committed/
Swedish Energy Agency
Committed/
SenterNovem
Norway
Sweden
Netherlands
Germany
Committed/
Ministry of Environment,
Nature Conservation and
Nuclear Safety
South Korea
Committed/
Ministry of Commerce,
Industry and Energy
Table 1 – Participating Countries
Organization












NREL
MIT
University of Massachusetts
GE Energy
RISØ National Laboratory
Vestas
Elsam
Siemens WindPower
DNV
Carlbro
Garrad Hassan
Ceasa



NTNU-BAT
Norske Hydro
Chalmers






ECN
We@Sea
Kema
University of Stuttgart
GE Energy
Repower

Korean Institue of Energy
Research
Inha University

The planned budget for running the Task is approximately $50,000 per year, which will be paid for
equally among the number of countries who join the Annex (e.g., with the eight countries joined up
to now, the cost in U.S. dollars is $6,250 per country per year). Each country may have several
participating organizations for a single membership fee, with the hope that more organizations will
lead to more robust results. It will be the responsibility of each country to determine how this cost
of membership is distributed among the individual organizations. It is expected that the task will
continue for a period of at least three years. The cost of participants own effort is paid by each
participant.
Subtask 1 – Experience With Critical Deployment Issues
Denmark, through RISØ National Laboratory, will serve as operating agent for subtask 1.
AS a first step workshops have been planned for the three research areas. The host country will
assume the responsibility for each research area until formal research plans are adopted.
IEA Task 23 – Global Wind Power 06, Adelaide Australia, September 21-22 2006
4
Regarding research Area 1: Ecological Issues and Regulations the Netherlands has agreed to host
the first workshop, but a meeting date has not yet been set. The areas of collaboration to be
discussed are:






Baseline data and research methods
o Develop methods to share baseline data and research methods for pre- and postconstruction studies.
Impacts on the environment (assessment criteria)
o Summarize preliminary conclusions from environmental impact assessments among
nations that have offshore facilities. (This area is similar to one of the objectives of
Concerted action for Offshore wind energy Deployment [COD]. This annex will
collaborate with these activities whenever appropriate.)
o Evaluate potential cumulative effects to the marine ecology.
o Compare methodologies and preliminary conclusions from avian and mammal
surveys.
Permitting process
o Evaluate streamlining of planning and approval procedures.
o Educate the regulators and facilitate interagency cooperation.
Pre- and post-construction monitoring of operating wind facilities
Public (stakeholder) involvement and acceptance
Decommissioning processes and procedures.
Research area 2
UK has hosted the first workshop on Electrical System Integration at Manchester University 12-13
September 2005. The workshop discussed the technical options and the role of enabling
technologies in achieving reliable design of offshore connections. This included the development of
offshore grids for collection and transport of significant amounts of power to the shore and the
integration with the onshore transmission network. Also, cost effective integration of offshore wind
generation will require the development of systematic and consistent approaches to resolving a
number of technical, commercial, and regulatory issues. These include license conditions, offshore
security standards, transmission charges, grid code, connection and use of system codes, all of
which were included in the scope of the workshop.
Based on a number of presentations on experiences from existing offshore wind farms and the
planning process, the delegates at the workshop in Manchester concluded that the following topics
were the most important for further work under Task 23:





Technical architecture of offshore grid systems and enabling technologies.
Grid Code and security standards for offshore versus onshore
Offshore wind meteorology and impact on power fluctuations and wind forecasting
Control and communication systems of large offshore wind farms
Behavior and modeling of high-voltage cable systems
The working title for the working groups covering the subjects is suggested to be: Connection of
Offshore Wind Farms to Onshore Grids.
IEA Task 23 – Global Wind Power 06, Adelaide Australia, September 21-22 2006
5
Based on results from Manchester further planning work has taken place in a collaboration between
UK and Denmark. A draft project plan was formulated in December 2005 and revised July 2006.
This project plan formed the basis for a planning meeting at Risø National Laboratory August 16,
2006 with participants from UK, Germany, Sweden, the Netherlands and Denmark. At the meeting
changes were agreed in the draft project plan in order to take into account consideration about work
to be concentrated on subjects having high priority in as many countries as possible. The project
plan will include lists of projects for which member countries want to share gained experiences.
The differences in priorities in this area reflect the very different level of wind energy penetration in
the power systems of member countries. In some member countries the planning process for offshore wind farms means a strong concentration of the power production. In these cases the most
important question becomes the technical architecture of transmission lines having only the purpose
to carry the wind energy into central grid points or integrating the networks with other transmission
lines. In Germany and Denmark the penetration is as high as 7 % and 18 %, respectively, whereas
in the UK the share is below 1 %. This means that wind turbines in some countries are approaching
the stage where they necessarily have to react as other power stations, i.e. having functions for security of demand and supply together with regulating and controlling functions for grid frequencies
and voltages.
Research Area 3
Denmark has also hosted the first workshop for Research Area 3 (External Conditions, Layouts and
Design of Offshore Wind Farms) December 2005 at RISØ National Laboratory.
The purpose of the workshop in Research Area 3 was to explore the key issues and highlight the
topics related to the following areas:






Exchange, validate, and evaluate wind resource data and wind maps specific to regions with
high potential for wind development.
Share databases and innovations to enhance measurement accuracy of marine buoys
pertaining to long-term sea-state and MET-Ocean data.
Exchange technical information of wave loading prediction methods and validation
experience of wave loading on wind turbine structures.
Share experience with long-term measurement techniques and instrumentation at offshore
stations.
Evaluate various turbine array configurations in large, closely spaced farms and examine
critical parameters such as mutual shadow wake effects, affect on energy production,
fatigue, and ultimate loading.
Exchange technical experience with offshore forecasting to predict wind plant output.
Each of these research areas were narrowed in scope after the discussion and the following areas for
collaboration among participants were identify as appropriate.
1) Wake modeling and benchmarking of models
1. Step: Workshop on status existing works
2. Step: Workshop on evaluating the quality of models and results
2) Marine boundary layer characteristics
The marine boundary layer is defined here as the lowest ~1 km of the atmosphere between
the height of the geostrophic wind speed and the wave surface of the ocean.
IEA Task 23 – Global Wind Power 06, Adelaide Australia, September 21-22 2006
6
The role of the sub-task could be:
o To review current experience particularly with regard to developing wind farms in
coastal areas (~50 km from the coast)
o To assess the reliability of remote sensing methods offshore, including satellite observations, sodar and lidar where the aim is to observe wind and turbulence profiles
at 100 m and above and to include tall mast measurements where available
o To assess the accuracy of model predictions including local scale, mesoscale and
LES models as available.
3) Met-ocean data and loads.
To be formulated
A significant research area dealing with operation and maintenance issues was also considered a
high priority topic but the planning of a workshop has been pending the work under Task 11. So far,
the results obtained have not allowed a strong basis for a decision to be taken in Task 23 about the
topic.
Status of Subtask 2 - Technical Research For Deeper Water
– Offshore Code Comparison Collaborative (OC3)
The U.S., through the DOE National Renewable Energy Laboratory, serve as operating agent with
Walt Musial leading the Annex. The first meeting for this subtask was held on October 28, 2004,
following a workshop that was held in Washington D.C., to determine the research needs for
deepwater offshore wind energy technology, sponsored by the USDOE Office of Wind and
Hydropower Technologies.
Subtask 2 is intended to focus on technical issues associated with deeper water implimentation of
offshore wind energy. In practice it has included modeling of shallow water and deep water since
many of the modeling issues are similar and it is important to benchmark the codes for shallow
water where there is some experience. The official name of this working group is the Offshore
Code Comparison Collaboration (OC3). The group is led by Sandy Butterfield of the National
Renewable Energy Laboratory.
Currently conservative offshore design practices, adopted from marine industries, are enabling offshore development to proceed but if offshore wind energy is to be economical, reserve margins
must be quantified and uncertainties in the design process must be reduced so that appropriate margins can be applied. Uncertainties associated with load prediction are usually the largest source and
hence the largest risk. Model comparisons are the first step in quantifying and reducing load prediction uncertainties.
Objective and scope:
The objective is to identify and verify model capabilities & limitations, to establish confidence in
predictive capabilities and establish analysis methodologies. This will lead to identifying areas
needing further research and testing
The scope of this project should address near term needs of the industry as well as future needs.
Currently the industry is focused on bottom fixed shallow water applications, especially in Europe
where shallow water sites are plentiful. In the US, Norway, Japan, Spain, Greece, Korea and many
other countries deeper water sites are more common. This project should include support structures
IEA Task 23 – Global Wind Power 06, Adelaide Australia, September 21-22 2006
7
that are likely to become solutions for these markets also. The scope of this collaboration includes
technologies ranging from the current shallow-bottom monopiles to deep water floating platforms.
Water Depth: 5 m – greater than 200 meters
Support structures: monopiles to floating
Wave loading models: linear and non-linear (breaking)
Uncoupled and coupled dynamic models: FAST, ADAMS, BLADED, HAWC, HAWC2,
BHAWC and FLEX5 (as modified by Vestas, Elsam & Stuttgart)
Not included: aerodynamic models, turbulence models, various turbine types, controls
Approach
A multiphase project has been outlined in a project work plan. The first phase would be strictly analytical with the goal of verifying the analytical capabilities and differences of the codes of the participants. The second and third phases would compare codes with various support structures and
foundation models respectively.
The OC3 baseline turbine model has been adopted by two major UpWind Work Package teams as
their aerodynamics and foundation modeling research work. Also the code comparison work to
date has established a procedure and data base that could be used for future code verification exercises such as the one outlined in UpWind Work Package WP 1A1, Integrated Design Approach and
Standards. This WP calls for the development of a reference turbine as well as procedures for verifying models and codes. OC3 has provided a basis for both of these goals.
RESULTS EXPECTED
The results of the 2 Subtasks are expected to be:
(a) Published Technical Proceedings from the workshops focusing on one or more of the critical
research issues for grid system integration.
(b) Defined innovative collaborative research objects for connection of offshore wind farms to on
land grids with identified participating members of the work program.
(c) Results from the collaborative research efforts, identified an included in the Work Program (the
results will be coordinated by the project leads and one of the Operating Agents after each year and
results will be presented at various national and international conferences and the IEA Executive
Committee.).
REFERENCES
1. Web site for IEA wind Agreement Task 23. http://www.ieawind.org/Annex_XXIII.html
2. Web site for the European Wind Energy Association accessed May 19, 2004.
http://www.ewea.org/
3. Web site for offshore wind energy accessed Sept 1, 2005:
http://www.offshorewindenergy.org/
4. Siegfriedsen, Lehnhoff, & Prehn aerodyn Engineering, GmbH, Conference Proceedings of
Offshore Wind Energy in the Mediterranean and other European Seas, Naples, Italy April
10-12, 2003.
5. Elliott, D.L.; Holladay, C.G.; Barchet, W.R. ; Foote, H.P.; and Sandusky, W.F. Wind Energy
Resource Atlas of the United States, Solar Energy Research Institute, Golden Colorado,
USA, 1987. Website: http://rredc.nrel.gov/wind/pubs/atlas/
6. Musial,W.D.; Butterfield, S, “Future For Offshore Wind Energy In The United States”
Proceedings EnergyOcean 2004, W. Palm Beach, FL, June 2004.
IEA Task 23 – Global Wind Power 06, Adelaide Australia, September 21-22 2006
8