st always canceled out by changes in the output of the other wind turbines. (http://www.vtt.fi/inf/pdf/tiedotteet/2009/T2493.pdf)
The short-term variability in wind farm output is the most greatly reduced, as it takes hours for a single weather event to affect a significant share of a wind fleet spread over hundreds of miles. This short-term variability is the most important as this is what grid operators must accommodate by using fast-acting, expensive, and inefficient reserve generation, and fortunately wind energy adds little to the need for these reserves. Longer-term (over an hour or more) variations are far more easily and efficiently accommodated by grid operators.
Second, le Pair fails to understand that changes in aggregate wind farm output are combined with all other sources of variability on the power system, which cancels out many of the changes in wind output. Since the dawn of electricity more than a century ago, power grid operators have been kept busy 24/7/365 continually changing the output of power plants to accommodate changes in electricity demand and supply.
Electricity demand changes drastically as people turn appliances on and off and as factories come on and offline. Small changes in the weather can drastically change the number of people running air conditioners or electric heaters. Many changes in electricity demand are unpredictable or imperfectly predictable, which make them harder for grid operators to accommodate. Because most of these changes in electricity use are random, much of the time electricity demand is decreasing when wind output is decreasing or vice versa, meaning that the changes in wind output are canceled out.
Similar to the unexpected changes in electric demand, all conventional power plants experience unexpected outages on a fairly frequent basis due to mechanical or electrical failures. These outages occur instantaneously and without warning, requiring grid operators to maintain enough fast-acting backup reserve generation 24/7/365 to replace the largest power plant on the grid, which is often the 1000+ MW needed to replace a large coal or nuclear plant. As noted above, these reserves are far more costly and inefficient than the slower-acting reserves that modestly increase in need at high penetrations of wind energy.
Le Pair also assumes that all changes in supply and demand must be accommodated by fossil fuel power plants, even though in many parts of the world hydroelectric plants provide the needed reserves without any emissions penalty at all.
Le Pair’s rough and obsolete estimates for the emissions/efficiency penalty for operating a fossil fuel power plant at less than full load or cycling the plant are also considerably higher than real-world data indicates, as many fossil fuel plants can decrease their output by 1/3 or more without experiencing more than a trivial decline in efficiency. This is particularly true of modern fossil plants that are designed to operate very flexibly with minimal reductions in efficiency.
Finally, Le Pair ignores the findings of other studies that the emissions savings of wind energy are even larger than expected because wind energy tends to disproportionately displace dirtier and less flexible coal plants relative to less dirty and more flexible natural gas plants.
As a result of these flaws, le Pair’s estimates greatly overstate the challenge of integrating wind energy and any emissions penalty associated with integrating wind. The theoretical power system he envisions is completely different from how the actual power system operates.
Consequently, his results and conclusions that lead him to attack wind are a pure fiction that bears no relationship to what happens on the real power system. As a result, it is not surprising that his conclusions are contradicted by a large body of government and independent grid operator data and peer-reviewed studies, referenced in the links at the beginning, showing that wind energy does result in the expected savings of fossil fuel use and emissions.
As an added case study to illustrate the real-world