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Wind fleet unreliable  

Credit:  Paul Miskelly, The Land ~~

Dr Benjamin Ticehurst (Letters, The Land, November 24) seems to believe that building a large fleet of wind farms around the NSW countryside will forever remove the risk of dire climate change posed by the otherwise-required burning of fossil-fuel. Sadly, this view has no sound basis.

An examination of operational data shows we can be absolutely certain that wind generation can have no mitigating effect whatsoever on climate change. A retired electrical engineer with more than 30 years experience in energy research and development, I have examined in detail the electrical generation performance of the fleet of wind farms presently connected to the eastern Australian electricity grid.

This fleet has an installed capacity of some 2000 megawatts and is spread right across the grid for a distance of some 1100 kilometres in an east-west direction and some 500km north-south. Its performance is therefore representative of what we can expect from any proposed larger fleet of wind farms in this region.

Dr Ticehurst might be interested in the results of this analysis based on publicly available data.

The output can never be described as “smoothly varying”, as some commentators would have us believe. Indeed it is quite the contrary: it is constantly varying over a very wide range, and at times extremely rapidly.

On more than 30 occasions during the calendar year 2010 the total wind farm output plunged to less than two per cent of that installed capacity. Indeed, on some occasions the output was absolutely nothing at all. In addition, there are frequent, sharp, unpredictable changes in the output amounting to up to several hundred megawatts at a time.

On an electricity grid, where the load/generation balance must be managed second-by-second, this sort of behaviour is not only an absolute nightmare for the grid operator, it is totally unacceptable, because it has to be compensated for by varying the output of controllable generators constantly running, whose sole task is to balance wind’s vagaries.

To an engineer, this dive-to-zero failure is an example of what is called a “common-mode failure”: it is another way of saying that the entire wind generation fleet has failed at those times. Such a fault condition would never be tolerated in conventional, reliable plant. Indeed, the total failure of the entire generation fleet of a particular type of conventional generator, for that is what this event is, would result in an immediate, full-scale public inquiry, with heavy fines placed on the operators of such generation plants.

It gets worse. Because this is a common-mode failure, whether 10 or 100,000 wind farms were to be connected to the grid, there would still be the same unacceptable number of common-mode failures, but with an additional twist: the larger the number of wind farms, the larger are those totally unacceptable power excursions, making it even harder to control the grid.

The more wind farms that are connected to the grid, the greater the impact of wind’s inherent instability on grid reliability: more wind energy means an increasing likelihood of frequent, unpredictable, widespread blackouts across the eastern Australian grid.

As for Dr Ticehurst’s fond hope that more wind farms will mean that we can stop burning coal and gas, in fact seemingly perversely, the exact opposite would occur.

The results of the analysis show that each increment of wind generation requires the provision of fast-acting, controllable, backup generation: that is, each new 100MW of wind farms will require 100MW of new fossil-fuelled generation solely for backup.

Furthermore, each such 100MW of fossil-fuelled generation has to provide on average 60-70MW output because of the wind farms’ poor capacity factor.

Dr Ticehurst can rest assured that, if anything, the coal and gas industry are jumping for joy at the prospect of more wind farms.

PAUL MISKELLY

BE MEngSc (both degrees in Electrical Engineering)

Mittagong.

Source:  Paul Miskelly, The Land

This article is the work of the source indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.

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