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'.
The aim is to build turbines in a location where wind blows hard enough to power the turbines 97% of the time – this means that most, if not all of New Zealand’s wind farms are available to generate electricity 363 days of the year – not a lot of downtime! However, the wind doesn’t blow at the optimum speed for the turbine’s design all the time, so it doesn’t always deliver its full capacity to the grid.
Wind farm developers spend considerable effort measuring windflow and understanding local wind conditions when investigating wind farm sites. They use sophisticated computer models to identify good sites and then take actual wind speed measurements to finalise the selection of a wind farm site and turbine locations.
Generating potential of NZ’s wind
New Zealand is exposed to winds travelling across the ocean uninterrupted 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 difference, 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.
In New Zealand, most areas with a high average wind speed (Class I sites) tend to be in coastal areas or on exposed hill tops and ridgelines. However, with advances in wind turbine technology, sites with lower average wind speeds (Class II and III) are becoming economically viable.
What about when the wind is not blowing?
Wind generation does vary with the natural ﬂuctuations in wind speeds. Arguments that wind farms provide no beneﬁt when the wind is not blowing miss two crucial points:
- energy supplies for electricity generation are managed on an annual cycle, not a daily or hourly cycle
- New Zealand has storage-based hydro generation that provide a ﬂexible complement to variable wind generation.
Essentially, if we use wind generation when it is available, we can reduce hydro generation and keep some of the water stored in the hydro lakes. This water effectively becomes a battery of energy that can be drawn on to meet peaks in demand or to cover for wind on calm days.
Regional renewable energy assessments
The Energy and Efficiency Conservation Authority has worked with regional councils to identify what renewable energy resources they have in their area, and then how to integrate this information into their planning and strategy processes.
Regional reports for the following regions can be downloaded from the EECA website:
- Bay of Plenty
- West Coast