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Tuesday, 11 March 2014
11:15 - 12:45 Optimising measurement strategies to maximise project value: Is the industry making false economies at the expense of project value?
Resource Assessment  


Room: Llevant
Session description

Striking the right balance between costs and benefits when designing a measurement campaign has always been a challenge. Nowadays the situation is more complex due to:

  • sophisticated instrumentation options (and their limitations);
  • wind farms of larger spatial extent located in more diverse climates;
  • advanced flow modelling.

It is no longer a straightforward process deciding on the optimal measurement strategy to minimise uncertainties in the energy assessment for a specific project. Assessing the resulting financial benefit is just as challenging. The interpretation of the data for site classification and thus choice of turbine has also become more complex.

Learning objectives

  • Evaluate the most efficient use of instrumentation for a specific site
  • Understand and quantify the connection between measurement uncertainty and project economics and loads
  • Make a more accurate choice of turbine type
  • Express uncertainty variations across the site as the basis for cost-efficient measurement campaigns
Lead Session Chair:
Wiebke Langreder, Wind Solutions, Denmark

Co-chair(s):
Jan Coelingh, Vattenfall
Santi Vila Moreno AWS Truepower, SLU, Spain
Co-authors:
Santi Vila Moreno (1) F P Barbara Boureau (1) Jorge L. Ochoa (1) Jose Vidal (1) Michael J. Brower (2) Francisco Habib (3) Itamar Lessa (3) Erick Lima (3)
(1) AWS Truepower, SLU, Barcelona, Spain (2) AWS Truepower, LLC, Albany, NY, United States of America (3) Casa dos ventos Energias Renovaveis, Sao Paulo, Brazil

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Presenter's biography

Biographies are supplied directly by presenters at EWEA 2014 and are published here unedited

Mr. Vila Moreno has been working in the wind industry since the early 2000s, both in project development as well as in consultancy. He has been working, among others, on site identification, measurement campaigns, wind flow modeling, turbine layout design, as well as in the production of project energy and uncertainty estimates. He has a Degree in Physics (University of Barcelona) and a MSc. in Renewable Energy Systems Technology (Loughborough University). Mr Vila Moreno works as a Lead Engineer at AWS Truepower.

Abstract

Uncertainty Maps: How To Make The Most Of Your Measurement Campaign

Introduction

A shortcoming of current resource assessment methods is the lack of a rigorous model of how the uncertainty varies across a project site. In most resource studies, the uncertainty is assumed either to be constant or to vary in proportion with distance from the nearest tower. In reality, it varies in complicated ways according to topography, meteorological conditions, and locations and characteristics of measurement systems.

The purpose of uncertainty maps is to represent the spatial distribution of the resource uncertainty. Their use should lead to better design of monitoring campaigns as well as more optimal placement of turbines.

Approach

Wind flow modeling uncertainty is related to the degree to which wind conditions differ between points. The more two points differ in their wind characteristics, the more difficult it is for a model to accurately predict the resource at one point based on measurements at the other. Although distance can contribute to such differences, other factors such as terrain slope and aspect, variations in land cover, and temperature gradients can also be important. The challenge is to devise a quantitative measure of wind resource differences between points, and to link that measure to the wind flow modeling uncertainty.

Main body of abstract

We proposed two possible measures of wind resource variation, one based on the predicted directional speed-up ratios between points, the other on the predicted differences in directional frequencies between points. An analysis of data from a large number of tall towers at diverse wind project sites was conducted, and it was found that there exists a statistically significant relationship between the proposed measures and wind flow modeling errors. From this analysis we derived a function relating wind flow modeling uncertainty to the relevant parameters. This function allows the creation of uncertainty maps for any location and combination of measurements.
Uncertainty maps can support project development in several ways. For example, they can help answer such questions as, "Where should I place my next tower, and by how much will the uncertainty in energy production be reduced?" or “What is the best way to combine the information from my measurement systems to achieve minimum overall uncertainty in plant output?” They can also be used to design turbine layouts that maximize the P90 or P99 production, rather than the P50, thus lowering risk.

The presentation will introduce the concept of uncertainty maps, describe our method of creating them, and focus on its application to resource assessment through an illustrative real-world example.


Conclusion

Current practice in resource assessment fails to give adequate consideration to the spatial variation of resource uncertainty across a project site. A more rigorous approach using uncertainty maps can lead to better wind monitoring campaign and plant design. The method developed in this research, based on data from a diverse range of wind project sites, illustrates the value of this approach for resource assessment.


Learning objectives
The audience will be introduced to the concept of uncertainty maps and its several applications to different key aspects of wind resource assessment through a real world example.