IEA R&D WIND ANNEX XI
The Operating Agent
March 2010
To Members of the Executive Committee, IEA R&D Wind
RE: TOPICAL EXPERT MEETING
ON
MICRO METEOROLOGY INSIDE WIND FARMS AND WAKES BETWEEN WIND FARMS
Dear Colleague,
The Topical Expert Meeting on “Micro meteorology inside wind farms and wakes
between wind farms” has already been arranged. Date and venue for the meeting is as
follows:
May 5-6, 2010
National Renewable Energy Center ( CENER )
Sarriguren – Navarra ( Spain )
The meeting will begin at 09.00 on Wednesday and end around 15.00 on Thursday.
Would you please forward an invitation to 2-4 people from your country who will be
able to discuss the subject in detail. An introductory note to the meeting has been
prepared by CENER, see attachment.
Proceedings from the meeting will be distributed soon after the symposium. To assist
in this the participants are urged to bring along one copy of the material they want to
have included in the documentation.
Contact person at CENER is:
Ms. Julia Millano, CENER
E-mail jmillano@cener.com
Phone: (+34) 91 417 50 42 Fax (+34) 91 556 63 00,
Details on travel and accommodation are included in attached files.
Please inform me of the names of the participants from your country as soon as
possible. A registration form is attached to this letter.
Best regards
Felix Avia
E-mail: favia@cener.com - Phone: #34 914175042
Attachments:
1. IEA Background and meeting format
2. Practical arrangements
3. Introductory note
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IEA BACKGROUND AND MEETING FORMAT
The objective of IEA RD&D Wind Task 11 is to promote wind turbine technology
through cooperative activities and information exchange on RD&D topics of common
interest. The Topical Expert Meetings and Joint Action Symposia are of the workshop
type, where information is presented and discussed freely in an open manner. See the
following
web
page
for
more
details:
http://www.ieawind.org/Task_11/Task_11_HomePage.html and click on “General
description and meeting format”.
More information can be obtained from:
IEA RD&D Wind general www.ieawind.org
Annex XI information
http://www.ieawind.org/summary_page_xi.html
IEA official home page http://www.iea.org/
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PRACTICAL ARRANGEMENTS
There is no cost for participating in the symposium, except for your personal travel
and accommodation costs.
Date and venue
May 5-6, 2010
Wednesday and Thursday
National Renewable Energy Center ( CENER )
Sarriguren – Navarra ( Spain )
Registration on day 1 will begin at 08.30hrs on Wednesday 5th May 2009, with the
meeting starting promptly at 09:00hrs. On day 2 the meeting will reconvene at 09:00hrs
and will end at 15:00.
A technical Tour is planned Thursday form 15:50 to 17:30 to visit the Alaiz
Experimental Wind Farm.
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3. INTRODUCTORY NOTE
IEA TOPICAL EXPERT MEETING # 62
ON
MICRO METEOROLOGY INSIDE WIND FARMS AND WAKES BETWEEN WIND FARMS
Daniel Cabezon, Ignacio Martí
CENER
Background
Power output and feasibility of big wind farms deployed in large arrays may be
dramatically decreased by wake effects, largely influenced by local atmospheric
boundary layer. On average these power losses can reach 10-20% of the wind farm
power output. In addition to the power losses an increase on fatigue loading is generated
at those turbines operating under wake conditions.
Average evolution of power losses in wind farms may be affected by several effects
mainly related to the wind farm topology and local wind climate, characterized by wind
speed, wind direction, atmospheric turbulence and stability.
From this point of view, wind turbine wakes represents an interesting topic of study
due to the momentum deficit and the increased level of turbulence created by turbines
inside a wind farm may cause an important reduction in power output and an increase
on unsteady and fatigue loads on downstream wind turbines. Besides, a good
knowledge of the aerodynamics in the near wake region is essential to understand the
physics of power extraction by wind turbines.
Recently a Euromech Coloquium on Wind Turbines Wakes was organized to discuss
about this specific topic (Madrid, October 2009), and was clearly demonstrated the large
number of on going research activities, with the target to go deeper in the knowledge of
the physical phenomena of the wake effects inside Wind Farms, as well as the wake
effects between neighbor Wind Farms.
Techniques
The state of the art to estimate wake effects of wind turbines in wind farms, is to
solve the incompressible Navier-Stokes equations closed using CFD turbulent models
coupled to actuator disk-type approximations of wind turbine rotors.
Due to the fact that the cost of computers is decreasing, modelling wind turbines and
wind farms wakes using CFD methods is an alternative to the faster engineering
models.
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Wind turbines are modelled as actuator discs in atmospheric flows using RANS
methods. Turbulent length scales inside wind farms are modelled at the same time. The
RANS methods are modelling all the scales of turbulence together, estimating an
equivalent length scale and velocity scale. These two scales are combined to form the
eddy viscosity concept. The Reynolds stresses are then estimated using this eddy
viscosity and the local wind speed gradient using the so-called Boussinesq
approximation.
The different size in turbulent length scales between the freestream flow typical of the
atmospheric boundary layer and the wake flow inside wind farms introduces an
imbalance problem and supposes a real challenge to the turbulence models used in
RANS methods, unsolved up to now.
TOPICS TO BE ADDRESSED
The main objective is to hold a meeting to discuss and gather information on:

Numerical and analytical models of wind turbine wakes in wind farms

Turbulence closure models

Experimental work based on wind tunnel and full scale field
experiments.

Influence of atmospheric stability

Influence of topography

Fatigue and loads

Offshore wind farms
The participants are encouraged to prepare presentations relevant to these objectives.
EXPECTED OUTCOMES
One of the goals of the meeting will be to gather the existing knowledge on the subject
and come up with suggestions / recommendations on how to proceed for future
developments. Based on the above a document will be compiled containing:




Presentations by participants
Compilation of the most recent information on the topic
Main conclusions of the discussion session.
To define IEA Wind RD&D’s future role in this topic
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TENTATIVE AGENDA
The tentative agenda covers the following items:
1.
2.
3.
4.
5.
6.
7.
Introduction by host
Introduction by Operating Agent, Recognition of Participants
Collecting proposals for presentations. The participants are encouraged to
inform the Operating Agent on the contents of their presentation in advance
and if possible provide a copy. The participants are also encouraged to in
advance suggest relevant discussion matters that would have their interest.
Presentation of Introductory Note.
Individual presentations
Discussion
Summary of meeting
Intended Audience
The national members will invite potential participants from research institutions,
utilities, manufacturers and any other organizations willing to participate in the meeting
by means of presenting proposals, studies, achievements, lessons learned, and others.
This means then that the symposia will be wide open, taking into account that it is the
first time that this subject will be discussed within the framework of the IEA Wind
RD&D.
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