Wind Power: Too Good to Be True? (Part 1 of 3)

My Granddaddy taught me that if something sounds too good to be true, it usually is.

This is likely the reason I grew up to be something of a skeptic, a dyed-in-the-wool researcher, and a lover of footnotes and bibliographies. When somebody makes a claim, I ask to see the evidence.

Wind power sounds just about as good and “green” as it gets. Advocates claim that industrial wind utilities are “farms” and their operators altruistic “farmers” whose windmills “harvest wind for America”, saving us from the scourge of fossil fuels. Advocates claim that wind is a reliable, sustainable, clean and commercially viable energy source.

Sounds great. But is it true?

Wayne Brunetti, former CEO of Xcel Energy, the nation’s top wind power provider, said, "We're a big supporter of wind, but at the time when customers have the greatest needs, it's typically not available." Brunetti is referring to the inverse relationship between the windiest time of year, which is winter, and the time of year when Americans use the most electricity, which is summer.

Virtually all air conditioners are powered by electricity; however, according to the US Census Bureau, only 30% of Americans use electricity for heat, and most of those homes are in Southern states. The Northeastern, Mid-Atlantic, and Midwestern states (where wind power is growing the fastest) use natural and LP gas, fuel oil, and kerosene for heat.

A power source that provides the least power when power is most needed doesn’t sound particularly reliable. Is it?

When a wind utility says it will add 39 megawatts of electricity to the grid, this number refers to “peak power potential”, or the maximum power the utility can produce if every wind turbine is operating at optimum wind speed. The average output is always much lower.

The “capacity factor” for a wind turbine is the ratio of average power output to peak power output. Peak power output occurs when wind is strong enough but not too strong; typically during a sustained wind of 30 mph. As wind slows, power output falls off dramatically. Ironically, in high winds (typically 60 mph or more), turbines are locked down.

According to “The Capacity Factor of Wind Power” (Bruno De Wachter, The Global Community for Sustainable Energy Professionals, 2008) the global average capacity factor for wind power is 19.6%.

Watcher makes the fascinating point that the greater number of wind turbines in the country, the lower the capacity factor. Countries with well-exploited wind resources tend to have a lower capacity factor. Germany, for instance, has a capacity factor of only 16.9%. This is because the best sites get developed first, and subsequent development goes into sites with poorer wind characteristics, thus reducing the average capacity factor. The U.S. still has a relatively high average capacity factor (28.8%), meaning that it still has a large wind development potential left to exploit, but at an ever-diminishing capacity factor. Fewer megawatts per acre, or per dollar.

Nonetheless, both the British and the American Wind Energy Associations (BWEA and AWEA) assume a capacity factor of 30%. Every wind utility in the U.S. bases their energy production estimates on the assumption that they will run at peak power at least 30% of the time, which is higher than it should be, but still pretty low, compared with the 75% average capacity factor of a coal-fired power plant.

Okay, but any power wind turbines add to the grid means less power coming from conventional sources, like coal-fired power plants, right?

Unfortunately, it’s not quite that simple.

The grid can’t store electricity. The grid is designed to provide electricity on-demand. A wind power utility can’t be made to increase or decrease its output in response to consumer demand, such as is caused by seasonal changes in the temperature. Wind turbines respond only to the wind; their electrical output increases and decreases in response to wind speed, which, needless to say, we humans can’t control.

So, the grid responds to this constantly fluctuating electricity production as it would to a large and erratic consumer. In other words, when there is a surge in wind power, there is a drop in demand from the coal-fired power plant; and when there is a drop in wind power, there is a surge in demand from the coal-fired power plant.

Simply stated, wind can be a supplementary source of power to the grid. But it can never replace conventional sources of constant, reliable power that provide what is known in the industry as a “base load.” Why? Because power companies have to be able to cover the base load even when the wind stops.

Think of it this way: If power companies were unable to cover the base load, then during those hot, still summer days when the wind simply stops blowing, your air conditioner would simply stop blowing.

Okay, so, even if wind turbines can’t supply all our electricity, each one helps reduce our total carbon emissions, right?

Again, it’s not that simple.

According to the National Academies Report “Environmental Impacts of Wind Energy Projects” (2007), Department of Energy (DOE) projections for US onshore wind power development indicate that wind power will supply between 3.5 and 19% of the expected increase in demand for electricity between now and 2020. This means that between 81 and 96.5% of new electricity generation must be obtained from other sources.

If this is true, it means that increases in wind power (as projected by the DOE) won’t result in a decrease in our dependence on electricity generation from other sources, the majority of which produce carbon dioxide.

In their report, the National Research Council states that between now and 2020, wind power will offset emissions of carbon dioxide by 1.2 to 4.5% from the levels of emissions that would otherwise occur from electricity generation. As of 2007, electrical generating units accounted for 39% of total U.S. carbon dioxide emissions from energy use.

What does this mean?

Well, if carbon dioxide emissions from electrical generation don’t increase between now and 2020, then wind power will offset a maximum of between 0.5 and 1.8% of carbon dioxide emissions from energy use. And if emissions do increase (because electricity demand continues to rise, as expected), then the wind power development anticipated by the DOE will offset less.

But, what if the DOE’s assumptions are all wrong?

What if Americans decide to build enough wind turbines between now and 2020 to offset the entire 39% of carbon dioxide emissions from energy use?

How many wind turbines would it take to accomplish this?

Good question.

According to the DOE, coal was responsible for generating 2,016,456 gigawatts of electricity in the U.S. in 2007.

So, let’s take the best-case example of a nineteen-turbine wind utility with a rated capacity of 39 megawatts, or 2 megawatts per turbine.

Two megawatts X 24 hours X 365 days X 30% capacity factor = 5256 megawatt hours. As discussed above, a 30% capacity factor is a pie-in-the-sky projection for the wind industry.

When I divide 5256 megawatts into the total gigawatts generated by coal in 2007, nearly 400,000 wind turbines would be required to replace the coal we were using to generate electricity at 2007 levels.

But let’s keep in mind that coal accounts for only about half of electricity production.

According to the DOE, petroleum liquids (49,505,000 megawatts), petroleum coke (16,234,000 megawatts), natural gas (896,590,000 megawatts), and other gases (13,453,000 megawatts) accounted for a total of 975,782,000 megawatts used back in 2007. To replace the energy produced from these fossil fuels would require close to an additional 200,000 turbines. These calculations do not replace the 21% of electricity generated from nuclear power.

Even so, removing only fossil fuels from the equation mandates the need for nearly 600,000 400-foot-tall, 285-foot-wide, 2 megawatt wind turbines. And that's if we returned to 2007 electricity usage levels, and if every turbine produced 2 megawatts at a 30% capacity rate, all day, every day.

What a wonderful world it would be, huh?

If the wind blew no less than 30 mph and no more than 60 mph all day, every day, everywhere. And if we had six 40-story turbines planted every square mile for 3.79 million square miles.

(See Part II for an inquiry into the Sustainability of Wind Power)