Transpower wants to know which way the wind blows

National electricity grid operator, Transpower, is investigating the potential for a computer system to forecast the amount of electricity likely to be generated at any given moment from wind.

On a Government tenders website request for information, it said it wanted to know wind generation forecasts for up to a week ahead, and the likely timing of variations in the amount of power produced each hour.

Transpower said that while the current level of electricity generated from wind turbines, about 550MW, did not cause big problems for the security of the grid supply, "the addition of the currently consented 3000MW of generation will present operational challenges for system management".

This was why it was interested in a wind generation "forecast tool": a sudden drop in the wind over any large area when there was heavy electricity demand could throw strain on the national grid.

Some thermal plants fired by coal could take up to 10 hours to bring online to replace the electricity lost when the wind dropped.

"Forecast data would be available to system co-ordinators in real time to enable less conservative approaches to maintaining grid security to be undertaken," Transpower said.

Its managers want to be able to view forecast not only for individual windfarms, but the collated forecasts for each island. Most electricity sent across Cook Strait goes north, except when the southern hydro lakes run dry, but a period of calm stable weather over the South Island could require electricity to be sent south if the windfarms there were becalmed.

WeatherWatch analyst Phillip Duncan said detailed hour-by-hour forecasts were increasingly common in other countries such as Australia, the United States, Canada and Cuba.

In America, hour-by-hour forecasts had become standard, using "grid forecasting" where historical weather patterns, and geography could be combined with a computer model of predicted weather to create an accurate forecast. One US website,, was just a computer generated forecast from Atlanta with no human input, but was able to accurately predict snowfalls in Timaru which were not signalled by human forecasters in New Zealand.

Mr Duncan said computer-generated forecasts of wind and its strength in New Zealand were often inaccurate and even human forecasters struggled to accurately predict win in some regions.

"Canterbury is one of the hardest places to forecast," he said.

"Sometimes we have nor'easters that are light but cold in Christchurch ...but a few kilometres down the road it's a hot, gusty nor'wester."

But windfarms were typically in areas easier to forecast, with constant strong prevailing winds.

Central New Zealand, from Marlborough to Wairarapa and Manawatu was "solidly" windy and easy to predict, and Stewart Island and coastal Southland were even better.

"We can see wind events sometimes 10 days in advance, especially in winter," Mr Duncan said.

Outside of areas such as Manawatu, Wellington and Marlborough, the electricity sector would benefit having a meteorologist working for them, with access to wind turbine outputs.



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