Sunday, September 20, 2009

Wind Power - Part 1

The push by many Governments around the world to embrace renewable forms of energy to meet targets set to reduce greenhouse gas emissions, has seen an explosion in the number of wind farms popping up in many countries.

As can be seen in the above graph, even the U.S. which is often criticised for having a slow uptake of renewable technologies in 2007 the Bush administration had an 916% increase in wind power generation.

It was
David Bellamy who paid a hefty price with his television career for pointing out on the BBC children’s show Blue Peter that he believed that:

wind generators were an inefficient way of generating Electricity and required a coal fired or nuclear power station as back up for when the wind didn’t blow hard enough or indeed too hard, to maintain capacity to the grid.

So was he right or were the BBC right to sack him for misleading the children? Journalist Terry McCrann examined the case of Denmark who have converted much of their generating capacity to wind powered renewable. What he found was:

When the wind doesn't blow, power doesn't flow even in Denmark.

At 12.17am, as steady winds swept in from the North Sea and most Danes were in their beds, the nation's wind farms churned out 70 per cent of the electricity being consumed across the country. "Barely 48 hours later, those wind farms were supplying all of 2 per cent of the electricity being consumed across Denmark.

From a bracing 2300MWh/h or so the output of two largish conventional power plants to less than 100 MWh/h, barely enough to keep the night lights burning. When the wind don't blow, the power don't flow.

So when that happened, where did the electricity come from?

From Norway, from Sweden and from Germany.

Indeed, when the wind doesn't blow in Germany ,which now gets high single digits of its total power from wind , it goes to nuclear France.

All up, around 1500MWh/h for some hours. In effect, the three neighbours jointly running a very large conventional power station just to keep the lights on in Denmark.

On average, across a year, you might get 30 per cent of its theoretical capacity, but often you get zero or so close to zero as not to matter. It happens frequently and at any time; and when the wind chooses, not you.

Another example, less than 10MWh/h, effectively zero, across all of Denmark for four hours straight. Back in February, less than 100MWh/h for 36 hours straight. If you were relying on wind, a day and a half with no power.

So, an average of less than a third of maximum capacity in a twelve month period and at times no power generation at all. Also, being forced to buy power from neighbours with nuclear or coal fired capacity as a back up during those times and due to the unpredictability of the downturns that capacity must be available instantly at any time. Maybe Dr. Bellamy had a point. But are there any other examples of similar dropouts, etc?

In this article from the Energy Tribune it examines the United Kingdom’s wind power program:

..this summer, the U.K., under pressure to meet an ambitious E.U. climate target of 20 percent carbon dioxide cuts by 2020, assumed the mantle of world leader in wind power production. It did so as a direct consequence of the U.K. Government's Renewables Obligations Certificate, a financial incentive scheme for power companies to build wind farms. Thus the U.K.'s wind operation provides the ideal case study -- and one that provides the most complete conclusions.

The U.K. has all the natural advantages. It is the windiest country in Europe. It has one of the continent's longest coastlines for the more productive (and less obtrusive) offshore farms. It has a long established national power grid. In short, if wind power is less than successful in the U.K., its success is not guaranteed anywhere.

Variability is one of the chief criticisms levelled at wind power.

When the wind drops or blows too hard, turbines stop spinning and you get no power. Wind turbine advocates have claimed that this can be avoided by the geographical spread of wind farms, perhaps by creating an international super grid. But, as Oswald's report makes clear, calm conditions not only prevail on a fairly regular basis, they often extend across the country with the same conditions being experienced as far away as France and Germany.

Worse still, says Oswald, long periods of calm over recent decades occurred in the dead of winter when electricity demand is highest.

Periods of low wind means a need for pumped storage and essential back-up facilities. Oswald told The Register online news service that a realistically feasible U.K. pumped-storage base would only cope with one or two days of low winds at best. As regards back-up facilities, Oswald states the only feasible systems for the planned 25 Gigawatt wind system would be one that relied equally on old-style natural gas turbines. As Oswald says however, the expense of a threefold wind, pump storage and gas turbine back-up solution "would be ridiculous."

But cheap gas turbines are far less efficient than big, properly sized base-load turbines and will not be as resilient in coping with the heavy load cycling they would experience. Cheaper, less resilient plants will mean high maintenance costs and spare back up gas turbines to replace broken ones that would suffer regular thermal stress cracking. And of course, the increasing use of gas for the turbines would have a detrimental effect on reducing carbon dioxide emissions are always one of the chief factors behind the wind revolution.

Oswald's report concludes also that the all this wear and tear will further stress the gas pipeline network and gas storage system.

"High-efficiency base load plant is not designed or developed for load cycling," says Oswald. Critically, most of the issues raised in the independent report have not been factored into the cost of wind calculations. With typical British understatement,
Oswald concludes that claims for wind power are "unduly optimistic."

So a similar experience for Britain then.

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