I HAVE a dream. To see the first of -- almost -- all the wind towers torn down.

Like the bits of the Berlin Wall, we'll keep a few as reminders of an embarrassing past; a time around the turn of the century when society collectively took leave of reason.

Going from the 20th century not into a more enlightened 21st century, but back to a 14th century future of weird religious cults and wandering prophets warning of the coming end of the world.

Wild-eyed wandering prophets, albeit these days wandering by plane? Our Black Death? I wonder if you can guess.

In very simple terms, if wind farms are the answer, the question must be: how can we waste the most money in an utterly useless exercise?

Yes, we might end up tearing them down. But that won't bring back the tens of billions of dollars that will have been wasted.

And which, as Danish statistician Bjorn Lomborg explains with out-of-time analytical logic, could more effectively be spent dealing with the consequences of climate change.

If the climate is indeed a-changing; and critically, if it's changing no matter what the cause or causes.

Causes, plural? Imagine waking up one day and discovering we'd cured the 'carbon disease'. But the world was still getting hotter.

The expensive uselessness of wind power was perfectly, if unintentionally, captured by energy company AGL's announcement on Monday that it would be spending $166 million to build a new 'wind farm' in the Hallett area of South Australia.

What nailed it so perfectly was a coincident announcement the same day by mining company Xstrata and infrastructure group APA. They had opened a new power station at Mt Isa in Queensland.

This though was not a wind farm, but a gas-fired plant. The duo claimed it would be 'low-emission'. But of course gas is still a hydro-carbon.

They would have done better to make the point that Xstrata's mine and Mt Isa city need power all the time. Even when the wind don't blow.

The comparative arithmetic though is the really interesting bit.

APA's gas plant cost $38 million and will produce 30 megawatts (MW) of power. Excluding time-out for maintenance, all the time, 24/7.

AGL's plant is costing $166 million and has 'capacity' of 71MW.

Straight up it's considerably more expensive. Scaling up the gas plant would get you 71MW for a capital cost of $90 million, not $166 million.

But then, you are not actually getting 71MW out of the wind farm. You only get that when the wind, ahem, blows. And not too fast, mind you!

You will on average get somewhere between 18 per cent and 33 per cent. So you are in fact paying $166 million for between 13MW and 23MW of real capacity.

Let's be generous and assume the wind blows more than not, and use the upper figure.

So the comparison becomes $38 million to get 30MW from gas and $166 million to get less -- 23MW -- from wind.

That's to say the comparative capital cost of this wind farm is six times that of the gas plant.

And then understand that gas is an expensive form of carbon-based power generation. Especially with an oil price hovering around $US100.

Ah, but that's capital cost. Operating wind is so much cheaper because the wind is free. Yes, the wind might be, but not the turbines. And it takes a lot of years of cheap input to make up for an upfront capital cost six times as high.

Plus there's that other little problem with wind. To cover for when the wind don't blow, you have to build the 30MW gas plant anyway. Or its equivalent somewhere in the system.

Wind only 'works' when it can be part of a very large electricity grid. So when the wind contribution goes down to zero -- and it can stay at zero for days -- the loss can be covered for by conventional power.

Lomborg's home country Denmark has the biggest wind power base of any country in the world, getting half its electricity from that source.

But at times it gets zero from wind. It then has to bring in power from Norway, Sweden and Germany.

This only 'works' because Denmark is tiny compared with especially Germany, whose power is generated mostly by coal and nuclear.

So when Denmark demands what is a huge amount of power in its terms, with very little warning, the drain is tiny on its combined neighbours.

In short, even in its own terms wind could never be more than a marginal part of the power grid. We don't have a 'nice' Germany as a neighbour.

And even then we would still have to build two power stations for every wind one. For when the wind don't . . .

mccrannt@heraldsun.com.au