Click to enlarge Te Rere Hau Click to enlarge Southbridge Click to enlarge  Te Apiti Gebbies Pass Click to enlarge Tararua Click to enlarge Brooklyn Click to enlarge Haunui
A Wind Energy Job?
Click to enlarge Te Rere Hau Click to enlarge Southbridge Click to enlarge  Te Apiti Gebbies Pass Click to enlarge Tararua Click to enlarge Brooklyn Click to enlarge Haunui

70 metre wind mast at Belmont, Wellington. Courtesy of Greater Wellington Regional Council

New Zealand wind resource

New Zealand is generally recognised as having has one of the best wind resources of any country in the world thanks to its location, with the country lying across the prevailing westerly winds in an area long referred to by sailors as the 'Roaring Forties'.

As an island-nation located in the middle of the Pacific, New Zealand is exposed to winds traveling across the ocean un-interrupted by other land forms. A fairly steady succession of troughs and depressions passes to the east of the country, creating the predominantly westerly wind flow.

As each of these weather systems passes the country it creates a pressure, and therefore wind flow pattern over the mountains. In some locations this wind flow is just about continuous and can be of relatively high speed, making these areas well suited to wind energy development.

The measurement of wind speed is vital for providing wind farm developers with a good understanding of the best locations for wind farms. To finalise the selection of a wind farm site developers typically take actual wind speed measurements but before this they can try and predict where the best sites will be using sophisticated computer models.

Actual wind speed measurements are made using anemometer installed on 'met masts’. In some cases these masts can be as much as 80 metres tall to measure the speed at the expected hub height for the turbines (as shown in the photo to the right, from Belmont in Wellington ). This method is the most accurate but is typically also expensive which is why models that predict average wind speeds based on historical data from national weather data are used to select a site in the first instance.

This modeling can be done at four levels of accuracy: Synoptic scale modeling looks at weather systems covering areas of several hundred miles or more. Meso-scale modeling covers the range down to about 10 kilometres . Storm scale modeling refers to the analysis of individual weather events (e.g. thunderstorms) and consequently is concerned with features ranging in size from a kilometre up to 50 kilometres. Micro-scale modeling is concerned with modeling wind speeds at a resolution down to as low as 200 metres. A combination of Meso- and Micro-scale modeling is usually used for site identification.

The attached wind map has been prepared by NIWA based on data collected from climate stations throughout the country over the period 1971-2000. The long-term median values are calculated at each station site and then these values are interpolated onto a 500 m by 500 m grid. The map is then created from this gridded data. The interpolation uses special techniques to take the proximity of the climate stations and the topography into account.

Due to the scale of the map you may not be able to see all of the areas where high wind speeds might provide for a wind farm development. For a more detailed view of a particular region of New Zealand you can use NIWA’s “Climate Explorer” that is available here (http://climate-explorer.niwa.co.nz).

Even these local maps might not identify all of the areas where wind speeds might be high enough for a wind farm, due to their scale. Wind farm developers investigate down to a very high resolution (as close as several hundred meters) to identify sites. It should also be remembered that wind speeds are higher at higher altitudes so the wind speed at the turbine height is typically higher than that indicated on this map.

 

 

 

 

 

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