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Delegates are invited to meet and discuss with the poster presenters during the poster presentation sessions between 10:30-11:30 and 16:00-17:00 on Thursday, 19 November 2015.

Lead Session Chair:
Stephan Barth, ForWind - Center for Wind Energy Research, Germany
Alfredo Peña DTU, Denmark
Alfredo Peña (1) F Andreas Bechmann (1) Davide Conti (1) Nikolas Angelou (1) Torben Mikkelsen (1) Peggy Friis (1)
(1) DTU, Roskilde, Denmark

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2015 and are published here unedited

Alfredo is a Senior Scientist at the Meteorology section of DTU Wind Energy, Denmark. His work has mainly been focused on the study of the wind profile by combining ground-based remote sensing techniques with traditional instrumentation. He has been involved in many other aspects of wind power meteorology which include turbulence, wakes and the use of numerical weather prediction models for wind energy. He has a degree in Mechanical Engineering, a Master in Mechanical Engineering, a Master in Renewable Energies and did his PhD at Risø.


Poster Download poster (11.53 MB)


Should we really be concerned about obstacles in wind resource assessment?


In wind resource assessment we usually consider four main "phenomena" impacting the wind and thus the estimation of wind energy: the orography, the roughness (and roughness changes), the wakes and the obstacles. Although the latter is perhaps the most complex of all four, it is the less studied of them. This is mainly because we try to avoid deploying turbines close to buildings, trees, ow windbreaks which can directly shelter the wind flow. However, in some applications it is impossible to avoid obstacle effects like in the urban wind energy and small wind industry as in countries like Denmark small wind turbines need to be placed close to houses and farms due to planning regulations. Also, due to the less available sites with high wind potential, new sites on land might face more and more sheltering from nearby obstacles.


Our idea is to investigate how accurate shelter models are by evaluating them against a unique dataset of measurements of the shelter behind a solid 3-m tall and 30-m long fence that we have performed at our Risø campus in Roskilde, Denmark. The measurements were performed using the short-range WindScanner system from DTU ( in which three wind lidars (synchronized in time and space) measured the 3D wind field in the wake of the fence on a vertical plane grid extending ~2.5h (in the vertical) and ~10h downstream (h is the height of the fence).

Main body of abstract

Here we present a number of shelter cases analyzed from the lidar measurements representing a variety of wind speed, atmospheric and turbulence conditions, and wind directions relative to the fence position. Modelling results, from both engineering-like and CFD shelter models will be presented and discussed. These include the WAsP-shelter model used traditionally in many wind resource studies (and that is included in the Wind Atlas Analysis and Application Program- WAsP) and models alike which are also based on Perera's 1984 expression.


This analysis shows that:
1. Detailed consideration is needed to investigate the sheltering effects on the wind in order to improve our wind and energy predictions
2. Scanning wind lidars are today a feasible, interesting and accurate alternative to meteorological towers to perform measurements of the shelter behind obstacles
3. The engineering-based shelter models need to be improved and further evaluated in order to perform accurate wind energy estimates
4. New regulatory and planning guidelines for small wind turbines need to be developed in order to optimize the use of small wind turbines

Learning objectives
We would like that the audience:
1. Understands the impact of the shelter on the wind resource
2. Understands the importance for quantifying the shelter effect on the wind
3. Gets an idea of the accuracy of shelter models and expressions
4. Finds out about a unique database of shelter measurements which can be used for scientists and researchers worldwide