Monday, February 4, 2008

Not So(va)cool Again

Dr Benjamin K. Sovacool, the scourage of Blacksburg, is at it again. In a Scitizen editorial, Sovocool claims that renewable energy is just as reliable as fossil fuel (and nuclear) electrical generation plants.
Sovocool argument involves a logical slight of hand.   He begins by telling us:
All electricity systems, since they must respond (sometimes immediately) to complex interplay of constantly changing supply and demand, are highly variable. They are subject to unexpected failures and outages, and influenced by a large number of planned and unplanned factors. Renewables are merely variable in a different way than conventional sources, and in many cases their unique type of variability can help, rather than hurt, the electric utility system.

The key word in this statement is respond.  The problem with renewables is there inability to respond to demand.  It is true that fossil fuel and nuclear power sources have  both scheduled and unscheduled shutdowns.    One way to measure the reliability of a electrical generating technology is by measuring the plants' average capacity factor. The capacity factor is obtained by dividing average output by its rated generating capacity (energy produced during a given time period/rated generating capacity during that time period). Thus if a plant plants output equals 20% of its rated generating capacity, then the capacity factor is 20%. In 2001 the average capacity factor of the 103 nuclear generating plants in the United States was about 91. Since nuclear power plants shut down at least 5% of the time for repair and refueling, their 2001 reliability performance of American nuclear plants was very good, and in fact nuclear plants were the most reliable power generating technology servicing the American economy.   The capacity factor thus measures generating performance over time.  

How do the capacity factors of  renewables compare with nuclear output?  Ontario has excellent wind resources.  Research indicates that Ontario wind resources have a 17% capacity factor in the summer, and a 41% capacity factor in the winter.     The Ontario data reflects a widespread reality, summer winds are less reliable than winter winds.  This is less a problem in Ontario than in Texas, where electricity demand peaks on windless summer days.   Similar problems have been observed in California.   This problem appears to be national in scope.  Nor is the problem limited to the United States.  The 2005 Annual report of the German electrical grid operator E.ON Netz states that: 

Wind energy is only able to replace traditional power stations to a limited extent. Their dependence on the prevailing wind conditions means that wind power has a limited load factor even when technically available. It is not possible to guarantee its use for the continual cover of electricity consumption. Consequently, traditional power stations with capacities equal to 90% of the installed wind power capacity must be permanently online in order to guarantee power supply at all times.

Why not then eliminate wind power completely from the energy generation scheme?   Wind generated electricity supplement the electrical generation of old and inefficient coal fired power plants.   While the wind is blowing, inefficient fossil fuel plants can be kept "spinning" while burning much less coal than they would if they were producing full power.  But in the summer, you are going to see the coal fired plants typically operating at near full capacity.  The system does save grid operators money, because heavily subsidized wind power is cheap, but national goals for CO2 reduction will never be reached by relying on wind generated electricity.

Fossil-fuelled capacity operating as reserve and backup is required to accompany wind generation and stabilise supplies to the consumer. That capacity is placed under particular strains when working in this supporting role because it is being used to balance a reasonably
predictable but fluctuating demand with a variable and largely unpredictable output from wind turbines.  Consequently, operating fossil capacity in this mode generates more CO2 per kWh generated than if operating normally.  This compromising effect is very poorly understood , a fact acknowledged recently by the Council of European Energy Regulators. 

White adds

[T]he CO 2 saving from the use of wind in the UK is probably much less than 
assumed by Government advisors, who correctly believe that wind could displace some capacity and save some CO 2, but have not acknowledged the emissions impact of matching both demand and wind output simultaneously. As a result, current policy appears to have been framed as if CO 2 emissions savings are guaranteed by the introduction of wind-power, and that wind power has no concomitant difficulties or costs.  This is not the case.

White points out:  

Market forces will fix wholesale electricity prices at a level that discourages new investment in modern plant, and the focus on wind power for new generating capacity is likely to lead to the retention of old, low efficiency, coal-fired plant for an extended period .

But an increase in wind capacity will have to be matched by new conventional capacity required to cover winter peak demand when there is no wind.  This new capacity would be under-utilised, again raising the unit cost and deterring investment. UK demand will continue to grow, as forecast by National Grid Transco, and power shortages seem inevitable in the medium term if the “secure” generation  capacity needed to replace obsolete plant is not forthcoming.

In conclusion, it seems reasonable to ask why wind-power is the beneficiary of such extensive support if it not only fails to achieve the CO2 reductions required,  but also causes cost increases in back-up, maintenance and transmission, while at the same time discouraging investment in clean, firm generation.

Thus Sovacool's claim that "renewables are merely variable in a different way than conventional sources, and in many cases their unique type of variability can help, rather than hurt, the electric utility system," clearly understates the problem in the case of wind generated electricity.


DV8 2XL said...

I would take any information coming out of the Ontario Power Authority with a grain of salt. They are not involved with generation or transmission of electricity in that Provence, those are handled by others. Their role is primarily as administrators of various conservation programs. It is a political instrument.

Wind generation in Ontario is very minor contributer to the grid, and in reality is just a bone tossed to the Greens. Nuclear energy is and will continue to be the cornerstone of electrical production there.

Charles Barton said...

In this case I simply wanted to illustrate the seasonal variation in wind capacity factors. The Ontario figure was at hand. Winter wind appear to be more reliable than summer winds in much of North America.

Randal Leavitt said...

I am really pleased to see this information posted here. I have been trying to make this point repeatedly about wind. It is a dirty source of power. However, it appears to be so clean and so pretty when you see that iconic three-bladed flower contrasted against a blue sky. I believe that is why is has so much support - the image is obviously clean and simple, nothing scary, no math needed to explain it, just good old gears and wind that we all are familiar with. The ugly part, the coal backup system, is never shown. If it was always included in the picture the support for wind would fall.

Charles Barton said...

Wind generators have killed 13 people in the United States. Power reactors none.


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