The Renewable Energy Reality Check

[kristopher]

26. I think people deliberately spreading known misinformation like this should be banned from EE

Using this forum as a platform for disseminating misinformation and trolling is wrong. It is within the purview of the hosts to act on such behavior.

Doesn’t Wind Power Need Backup Generation? Isn’t More Fossil Fuel Burned with Wind Than Without, Due to Backup Requirements?

In a power system, it is necessary to maintain a continuous balance between production and consumption. System operators deploy controllable generation to follow the change in total demand, not the variation from a single generator or customer load. When wind is added to the system, the variability in the net load becomes the operating target for the system operator. It is not necessary and, indeed, it would be quite costly for grid operators to follow the variation in generation from a single generating plant or customer load.

“Backup” generating plants dedicated to wind plants — or to any other generation plant or load for that matter — are not required, and would actually be a poor and unnecessarily costly use of power-generation resources.

Regarding whether the addition of wind generation results in more combustion of fossil fuels, a wind-generated kilowatthour displaces a kilowatthour that would have been generated by another source—usually one that burns a fossil fuel. The wind-generated kilowatthour therefore avoids the fuel consumption and emissions associated with that fossil-fuel kilowatthour. The incremental reserves (spinning or nonspinning) required by wind’s variability and uncertainty, however, themselves consume fuel and release emissions, so the net savings are somewhat reduced. But what quantity of reserves is required? Numerous studies conducted to date—many of which have been summarized in previous wind - specific special issues of IEEE Power & Energy Magazine — have found that the reserves required by wind are only a small fraction of the aggregate wind generation and vary with the level of wind output. Generally, some of these reserves are spinning and some are nonspinning. The regulating and load-following plants could be forced to operate at a reduced level of efficiency, resulting in increased fuel consumption and increased emissions per unit of output.

A conservative example serves to illustrate the fuel-consumption and emissions impacts stemming from wind’s regulation requirements. Compare three situations:
1) a block of energy is provided by fossil-fueled plants;
2) the same block of energy is provided by wind plants that require no incremental reserves; and
3) the same block of energy is provided by wind plants that do have incremental reserve requirements. It is assumed that the average fleet fossil-fuel efficiency is unchanged between situations one and two. This might not be precisely correct, but a sophisticated operational simulation is required to address this issue quantitatively. In fact, this has been done in several studies, which bear out the general conclusions reached in this simple example.

In situation one, an amount of fuel is burned to produce the block of energy. In situation two, all of that fuel is saved and all of the associated emissions are avoided. In situation three, it is assumed that 3% of the fossil generation is needed to provide reserves, all of these reserves are spinning, and that this generation incurs a 25% efficiency penalty. The corresponding fuel consumption necessary to provide the needed reserves is then 4% of the fuel required to generate the entire block of energy. Hence, the actual fuel and emissions savings percentage in situation three relative to situation one is 96% rather than 100%. The great majority of initially estimated fuel savings does in fact occur, however, and the notion that wind’s variations would actually increase system fuel consumption does not withstand scrutiny.

A study conducted by the United Kingdom Energy Research Center (UKERC) supports this example. UKERC reviewed four studies that directly addressed whether there are greater CO2 emissions from adding wind generation due to increasing operating reserves and operating fossil-fuel plants at a reduced effi ciency level. The UKERC determined that the “efficiency penalty” was negligible to 7% for wind penetrations of up to 20%.

http://www.ieee-pes.org/images/pdf/open-access-milligan.pdf