29082011

Wind power in Australia...

Wind Power in Australia

People keep saying that we can use wind power via turbines in 'wind farms' to, in part, replace base load power. We look specifically at what wind turbines need to operate and at what wind speeds they need to operate, then we look at where in Australia the wind is available in general to do this and draw some conclusions.

What does a wind turbine need?

Wind turbines basically need wind with has three characteristics:

• First off it needs to be of sufficient wind strength to drive the turbine;
• Secondly the wind needs to blow at a consistent and continuous basis. Wind that is gusty is of no use to a wind turbine.
• Thirdly the wind needs to blow from a consistent or slow changing direction; winds that come from different directions rapidly are no use as the turbine cannot cut into the wind quickly enough.
  

According to Wind Turbine Characteristics turbines have a 'cut in speed' where the turbine can actually start turning sufficiently to generate some power. Then there is a point of rated power output where the wind is sufficient to enable maximum output. Then beyond that there is a 'cut out speed' where the wind is too much for the turbine and it needs to stop or risk literally blowing up.

Now the article gives the following figures for these three points.

• Cut-in speed = 3.5 m/s
• Rated output speed = 14 m/s
• Cut-out speed = 25 m/s

Now these figures need converting into something we can compare to wind speeds in kilometers an hour (i.e. multiple by  3.6) - so we get

• Cut-in speed = 12.6 km/h
• Rated output speed = 50.4 km/h
• Cut-out speed = 90 km/h

Now given these figures we can next look at where such winds actually blow.

Where the winds blow

Luckily BOM have a handy page of wind maps for Australia by season and the morning and afternoon. Now this is important as during different seasons you get changes in the strength and direction of the winds (in general) around the country as weather systems come and go.

I suggest you first look at the Summer 9am map to get a hang of how to read the wind roses. The way it works is that the size of the circular blob in the middle of each rose is how much is 'calm', i.e. no wind. Then each of the 8 compass directions is split in 10km/h wind segments, with each length by proportional to the wind of that strength measured at that location. There is no maximum speed given.

Now given that wind turbines need 50.4 km/h typically to operate at peak - can you see any roses with 4 segments with the 4'th segment being sizable? i.e. there is a good chance of the wind blowing at a rate to operate the turbine at a high utilization....

Actually you won't find any, there is a lot of wind blowing around 11 to 20 km/h range, which just turns the turbine, and lot less wind blowing in the 21 to 30 km/h range. So for Summer the chances of actually operating a wind turbine any where near its rated capacity is very small as the winds literally do not blow consistently at level to allow that to happen.

Now lets have a look at Autumn 9am. Slight change in that Queensland gets a lot of directional wind in the 11 to 30 km/h range - so they could generate power, but again no way will the turbines reach capacity.



So what about Winter 9am. This is pretty interesting as there are no clear strong winds from consistent directions being shown, expect the top of Queensland. What that means it that during Winter its unlikely wind power will produce consistent power at a useful level. Which is rather annoying as usually for most of Australia Winter (like Summer) is a high power usage period. So when you really need the power wind cannot deliver.

Conclusion

Basically wind power is an expensive unreliable way to generate power for general consumption. Further we show that given the basic wind rose information for Australia it is unlikely a wind turbine will usefully achieve its rated peak output for the majority of its operational life.