Wind Projects - Initial Site Selection

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The initial site selection is the first phase in the development of any wind energy project. In this phase appropriate sites should be identified and their wind potentials should be estimated. By identifying environmental, technical, commercial and political constraints of the sites the project developer can decide whether a more extensive feasibility study should be conducted. As a starting point many developers visit the possible project sites, gathering first impressions about topography and infrastructure (roads, dwellings, grid-connection). A central task in this phase, available environmental and technical data must be collected[1].

First estimation of energy yields and related data requirements

The data requirements for a first energy-yield estimation of a wind project are defined by the following function

where H is the number of hours with windspeed Ui and P is the value of the power curve for the proposed wind turbine for the windspeed Ui.

A wind speed distribution function provides information about the frequency of different wind velocities occuring during a year. The generation of these distribution function requires long-time (for minimum one year) measurement. Thus for initial estimation, regional available data should be used, providing only rough information but keeping the initial costs low. The so-called power distribution function (PDF) can be obtained from a wind atlas (for example the NREL Oaxaca Wind Energy Atlas[2] provides regional wind data for a state of Mexico). The US National Renewable Energy Laboratory (NREL) publishes information about wind speed distributions for many regions of the world on its Website[[3]]. PDFs are based on Weibull-Distributions and take into account local conditions like the roughness of the surrounding terrain (given by surface characteristics, obstacles and topology) are calculated for any wind direction using a divisions of 12 30° sectors. To use the values of the PDF in the function presented above, wind velocity values of all directions are integrated[3].

The power curve of a wind turbine depicts the energy output of the turbine at different wind speeds Ui. Paul Gipe suggests that the reliability of power curves especially for small wind turbines is limited[4], but for the initial estimation the available power curves are sufficient.

In case data availability is very limited (for instance only from remote weather stations), wind velocity modelling including meteorological data and site characteristics can be used.


Assessing Topography

Assessing local framework conditions

Information about grid-connection possibilities

If the wind project is supposed to be connected to the grid, it will be necessary to examine the local availability of the electricity grid. Local electricity suppliers have to be consulted concerning possible connection points, local grid capacity and likely costs of connection in the area[5]. If only a short line to the next connection point has to be installed, costs of grid-connection will be low and the environmental impacts of this easiest case are small. In some areas the line connects the wind project directly with the next transformer station. In case the grid-capacity at the transformer-station is not sufficient for the connection of the wind project, the station has to be extended with an additional segment. Very big projects contain a separat transformer station required for the connection of the project to high-voltage grids[6]. Taking into account this information the project developer knows, whether the grid-connection will cause high costs and environmental impacts due to a long distance to the next connection point. Thus it is important to initiate a dialogue with the local electricity supplier as early as possible.

Road access to the wind project site

Infrastructure adversely affected by wind turbines

Preliminary environmental considerations


Visual effects



Dialogue with local civic and planning authorities

References

  1. European Wind Energy Association (1999) European Best Practice Guidelines for Wind Energy Development, retrieved 7.7.2011 [[1]]
  2. Elliott D., Schwartz M., Scott G., Haymes S., Heimiller D. and George R. (2003) Wind energy resource atlas of Oaxaca, National Renewable Energy Laboratory, USA, [[2]]
  3. Burton T. et al. (2001) Wind Energy Handbook, John Wiley+Sons
  4. Gipe P. (1999) Wind Energy Basics - A Guide to Small and Micro Wind Systems, Chelsea Green Publishing Company
  5. European Wind Energy Association (1999) European best practice guidelines for wind energy development, retrieved 7.7.2011 http://ec.europa.eu/energy/res/sectors/doc/wind_energy/best_practice.pdf
  6. Gasch, R. (2010) Windkraftanlagen - Grundlagen, Entwurf, Planung und Betrieb, Vieweg und Teubner