What happens when the wind stops blowing?
Wind turbines only operate when the wind blows. At the moment, when the wind stops blowing, electricity continues to be provided by other forms of generation, such as gas or hydro. But New Zealand is one of the windiest countries in the world, so we have a massive resource waiting to be used. And in the future, all our electricity could come from a mix of complementary renewable sources - balancing wind power with hydro, solar, geothermal, biomass and in the future, wave and tidal power.

There is actually a lot of confusion about the reliability of different sources of electricity. No power stations are able to operate all the time without stopping. Many so-called reliable sources such as nuclear plants suffer from unexpected 'outages' when reactors must be shut down, often at short notice, for essential safety maintenance. Unreliability of this kind is far harder to deal with than the intermittency of wind power, as the amounts of electricity involved are generally much higher. By comparison the variation in output from wind farms distributed around the country is scarcely noticeable.

And the wind will never stop blowing everywhere in New Zealand at once. Different overseas studies have sought to determine the limit beyond which installing intermittent capacity (i.e. wind generators) starts to incur significant costs in order to maintain the stability of the electrical grid. The level varies but is typically 15-30% of the total installed capacity. Since New Zealand has a total installed generating capacity of 8,412 MW this 15-30% band would be equivalent to 1,200-2,400MW of wind turbine generators. Up to now (beginning of 2005) we have installed about 168MW. Of course we have to find out the maximum theoretical limit of wind energy on our grid, but it's still a long way to reach this limit.

It is true that we could never rely on wind turbines alone to provide for all our electricity needs. But it is also very important to note wind power and hydro are perfectly suited to each other. As New Zealand generates a remarkable energy amount from hydro dams this is very advantageous for us. Wind and hydro are well suitable because the volume of water flowing through hydro dams around the country can be reduced when the wind is blowing. In effect what this means is that the electricity generated by wind turbines can be stored as potential energy in water in hydro dams. This 'stored' wind energy can then be released and used to generate electricity when the wind is not blowing.

In future, hydrogen could offer a potential way of storing electricity from wind power. Excess wind power can be used to produce hydrogen through electrolysis, and then hydrogen can be turned back into electricity using a fuel cell, as and when it is needed.

For more information look at the NZ Wind Energy Association website

(1) www.windenergy.org.nz/FAQ/elecsupply.htm#nowind

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