HOW COMPLEX IS YOUR SITE?

What is this?

This is a tool which determines whether a given wind farm project area can be considered complex or not. Complex, in this context, refers to topography and land cover which may cause wind flow conditions that are not correctly resolved by linear wind flow solvers, and which may subject wind turbines to non-standard inflow conditions. Click here to find out whether your site requires CFD for free.

Why would I want to use it?

Complex flow conditions are a frequent cause of wind park underperformance and higher-than expected maintenance costs. If a site is treated as complex from an early stage, appropriate measurement campaigns and modelling techniques can applied to mitigate the inherent risks. In the context of a review of an advanced project, it can serve as a quick check that an appropriate methodology has been applied to the site.

How does it work?

The applet estimates site complexity at each turbine location based on topography and land cover. Site complexity is a non-dimensional quantity which indicates the percentage of complex (i.e. steep) terrain upwind in a given direction. In this respect it is similar to RIX, however the effect of land cover is also considered by virtually increasing the steepness of the slopes depending on the tree height and coverage.

Where does the tool get its input data?

Turbine locations and wind distributions are provided by the user. Topographic data is drawn from the publically-available SRTM dataset. Forest cover is indicated by the user as a percentage of the total area. Roughness is assumed uniform.

Does this applet use VENTOS?

No it doesn’t. No flow modelling is performed. Calculations are strictly empirical.

How do I use it?

The tool is designed to lead you through each step. Just click on the question marks for help on some specific terms used within the tool.

To summarize, a kmz file is loaded indicating the turbine coordinates, then a wind rose file (optional, as a tab file or copy-pasted from a spreadsheet), and finally the percentage of forested terrain is specified. The applet will return a topographic map of the area, complexity indices by direction, and a summary pdf report.

What are the figures I see, and what do they mean?

A table is provided giving the complexity indices per wind direction. Values highlighted in orange and red correspond to complex and highly complex terrain based on Natural Power’s experience. It is recommended that CFD studies are used on sites showing high levels of complexity. The colour plot is not a complexity map, it is simply a topographic map to allow confirmation that the input data used by the tool corresponds to what you expect.

How is my data used?

Natural Power treats all data in the strictest confidence and warrants that the information you provide will never be used or disseminated without your explicit authorization. In using the tool however you are granting Natural Power the permission to use the data you provide to improve the performance of the tool itself.

The applet does not work. What should I do?

The applet requires the Java JRE runtime to be installed. Most computers will have this installed by default. If not it can be downloaded for free from www.java.com provided your IS policy allows this. Sometimes just changing browser can resolve problems. You can also try to upgrade or re-initialize Java. Although the tool is electronically signed, some corporate policies may place restrictions on the running of java applets. This can be confirmed or otherwise by your IS helpdesk. If this still does not solve the problem then please let us know.