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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
Nikos Stefanatos C.R.E.S., Greece
Nikos Stefanatos (1) F Dimitri Foussekis (1) Fragiskos Mouzakis (1)
(1) C.R.E.S., Pikermi, Greece

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Presenter's biography

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

Nikolaos Stefanatos has a Mechanical Engineering Degree and a Phd Diploma in experimental wind energy aerodynamics. Since 1995 is employed at the Wind Energy Department of the Center for Renewable Energy Sources & Saving (CRES). His core activities are in wind turbine power performance, resource assessment and anemometer calibrations He is currently Head of the Laboratory for Wind Turbine Testing of CRES and representative of CRES in MEASNET Network, where he participates in the Power Performance Expert Groups and is coordinator of Anemometer Calibration Expert Group


Poster Download poster (9.12 MB)


Comparisons of Rotor Equivalent Wind Speed (REWS) in complex terrain using a 100m Mast and several remote sensing devices


In the next generation of standards for power performance measurements, which are currently in their final drafting stages, the use of a Rotor Equivalent Wind Speed (REWS) is proposed as an alternative to the hub height wind speed. On the same time, the use of Remote Sensing Devices is also introduced for measuring the wind speed as an alternative to mast based instruments. The limits of applicability, the comparability of different definition methods and the related uncertainties, are some of the issues that are still under discussion, especially for complex terrain sites.


The present work, aims to investigate the sensitivity of the proposed methodology, the measurement methods, and the sensing devices on the definition of the REWS. This is made by applying different scenarios for the estimation of REWS using data from campaigns including concurrent measurements from remote sensing devices and mast based instruments in a complex terrain site.

Main body of abstract

On the complex terrain site of CRES at Lavrion, a 100m mast is operated. Measurement campaigns have been made using three Lidars systems of different types (Windcubes v2 and v1, ZephIR) and prisms (30deg and 15deg) with concurrent recording of wind speed, wind direction, inclination, and meteorological parameters from mast based sensors on the 100m mast.
Data gathered are used to estimate the REWS wind speed following the definition given in the running drafts of the IEC 61400-12-1 standard. Various concepts were run, assuming wind turbines with different hub heights and different configurations of measurement layout. For each concept, sensitivity analysis the flow conditions (inflow direction, shear profiles, etc) were made.
A good correlation between measurements from RSDs and mast based instruments is usually seen with differences in the resulting REWS being small, but dependent on the flow conditions and measurement configuration.


Good agreements, but dependent on flow conditions. Clear definition of flow and meteorological conditions during measurement campaign and measurement layout is needed in order to assess the comparability and the associated uncertainties.

Learning objectives
• Understand the sensitivity of the REWS to the flow conditions and measurement configuration in complex terrain.
• Evaluate uncertainty related to different flow and measurement methodologies.