Small Wind Site Assessment

Learner Guide

Produced by the Institute for Sustainable Futures; UTS in partnership with the Alternative Technology Association and TAFE NSW - Northern Sydney Institute

Supported by the NSW Government as part of the
Energy Efficiency Training Program — visit savepower.nsw.gov.au

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The Office of Environment and Heritage and the State of NSW are pleased to allow this material to be used, reproduced and adapted, provided the meaning is unchanged and its source, publisher and authorship are acknowledged.

The Office of Environment and Heritage has made all reasonable effort to ensure that the contents of this document are factual and free of error. However, the State of NSW and the Office of Environment and Heritage shall not be liable for any damage which may occur in relation to any person taking action or not on the basis of this document.

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WIND ROSES

Wind roses indicate the frequency of winds, binned according speed and/or power, for different sectors (or directions).

There are a number of different formats which can be used to display wind roses. Below is that used by BOM in Australia.

The percentage of calm conditions is represented by the size of the centre circle - the bigger the circle, the higher is the frequency of calm conditions.
Each branch of the rose represents wind coming from that direction, with north to the top of the diagram. Eight directions are used.
The branches are divided into segments of different thickness and colour, which represent wind speed ranges from that direction. Speed ranges of 10km/h are used in these wind roses. The length of each segment within a branch is proportional to the frequency of winds blowing within the corresponding range of speeds from that direction.

Below is the style of wind rose commonplace in Europe, for the purposes of wind farm development. The description is taken straight from the DWIA webpage (

This tells you how much each sector contributes to the average wind speed at our particular location.

The innermost (red) wedge gives the same information as the first, but multiplied by the cube of the wind speed in each particular location. The result is then normalised to add up to 100 per cent. This tells you how much each sector contributes to the energy content of the wind at our particular location.

The red wedges tell us where to find the most power to drive our wind turbines. In this case we can see that the prevailing wind direction is Southwest.”