The power of the wind is 1/2 of area (turbine rotor diameter) × air density × wind speed cubed. There is a theoretical physical limit (Betz’ law) that no more than 16/27, or 59.3%, of the wind’s energy (power × time) can be captured. Modern wind turbines may reach 50% efficiency, but only within a certain range of wind speeds, which appear to be the average speeds for which the turbines are designed, but at which speeds they generate at only a fraction (around 1/3) of their maximum rate. As the wind speed increases, the rotors are increasingly feathered and efficiency plummets.
The brochure for Enercon turbines includes graphs showing the efficiency vs. wind speed.
In addition to being limited by Betz’ law, wind turbines must not interfere with each other, so they must be spaced quite far apart. The minimum distance is generally considered to be 3 rotor diameters perpendicular to the wind (possible only where wind is unidirectional) and 10 rotor diameters parallel to the wind. See, eg, www.wind-watch.org/documents/?p=984. Thus in an array of, say, 90-meter-diameter turbines (the blades of each machine sweeping a vertical airspace of 1.57 acres), each machine would require 810,000 square meters around it, or 200 acres. From that 200 acres, assuming a 2-MW turbine and an average rate of generation 25% of capacity (see https://wind-watch.org/doc/?p=3427 for U.S. averages; they are generally quite a bit less in Europe), the average power density is only 2.5 kW/acre.
Furthermore, that wind energy is intermittent, meaning other sources of electricity must be available, and variable, meaning other sources must be kept running to be ramped up and down as needed to keep the electricity supply exactly matched to demand. This means that wind is only adding to the grid and then causing other generators to run less efficiently, including burning fuel while not generating electricity. See http://kirbymtn.blogspot.com/2013/10/us-co-emissions-for-electricity-from.html and http://kirbymtn.blogspot.com/2013/11/how-much-does-wind-energy-reduce-carbon.html
2. Pertaining to health — I’ve heard very mixed messages about whether the health effects are of legitimate concern and I would like to hear your take on it. ... Any scientific information would be great!
21 published (peer-reviewed) studies: http://wndfo.net/wts
10 non-industry, non-government reviews: http://wndfo.net/revs
One hitch has been the term “annoyance” as used in these studies. In epidemiology it means to a degree that can cause health problems. The wind industry has instead used its colloquial meaning to characterize the problem as something people just need to get used to.
Even that flies in the face of the evidence that infrasound (frequencies below the threshold of conscious hearing) and low-frequency noise (ILFN) is probably responsible for much of the problem, because research suggests that people who are sensitive to ILFN become more sensitized with continued exposure.
The research showing that people complain more about wind turbine noise than other artificial sources at similar decibel levels is probably explained by the facts that it is unpredictable (depending on wind speed and direction), that it often occurs at night, and that it is a pulsating noise.
Basically, the wind industry is trying to stop research as it has just begun. Because, as the reviews conclude, the preliminary research clearly justifies concern and is already leading to revisions of noise regulations to consider lower frequencies and pulsating patterns. And if such regulations are justified for humans, they would also have to be considered for wildlife ...
3. For my own sanity, I’m wondering why on earth there is so much controversy! How can there be such polar opposite opinions and what is the truth ... in your opinion?
There is a lot of desperation and urgency to remedy the consequences of our high level of energy consumption, and big wind has exploited that, ever since Enron first realized that it could sell wind to environmentalists as an alternative to coal. Since concern about climate change came to dominate mainstream environmentalism after Al Gore’s movie, wind energy has been sold as our salvation. It became a “with us or against us” marker of one’s concern for the environment or sociopolitical team loyalty. Its own adverse impacts (mining, birds and bats, wild habitat) are then dismissed simply as being much less than those of fossil fuels (the other team), ignoring the fact the the reduction of fossil fuel burning because of wind energy is effectively nil, making wind’s impacts — many of them unique, such as the threats to raptors and bats, and the need to build over hundreds of acres at a time in rural and wild places — an addition, not an alternative. Even the American Wind Energy Association once admitted that the most ambitious wind program would only slow the increase of carbon emissions. And for greenhouse gases, there are still the problems of transport and heating. And animal agriculture. And hydrofluorocarbons.
The truth is that there is no free lunch. By approaching the problem with building more instead of using less, wind energy is only perpetuating it. And while people look to wind energy to save the planet, they are more likely to avoid doing things that would make a real difference. They are able to buy Enron-invented “green tags” (carbon credits) to “offset” their impact rather than actually reduce it.
So the polarity is indeed justified and inevitable. Once somebody realizes that wind is a nonsolution, and harmful itself without meaningfully mitigating other harms, it is clear that there is hardly a “middle ground”. And once someone who believes in wind starts to admit that it has drawbacks or that claims for its benefits are overblown, a cornerstone of mainstream environmentalism starts to crumble — and retrenchment becomes all the more fierce to avoid complicating “the message”.
4. One more question: What are viable solutions instead of wind energy, and if wind energy is here to stay what kind of regulations or changes are needed for it to be successful?
Frankly, there probably isn’t a viable solution right now to 8 billion humans consuming ever more resources, particular in a world economic model of “growth”, which even with the modifier “sustainable” is still growth — growth of consumption, growth of waste, and less for the rest of life on the planet. Thursday's Democracy Now had a couple of climate scientists on calling for radical change from that model: www.democracynow.org/2013/11/21/we_have_to_consume_less_scientists.
As for the potential success of wind energy, it would require not only massive building of wind turbines (and all the resources they require) but also an even more massive battery backup system (and all the more resources) and a massive expansion of continent-wide high-capacity transmission lines. In other words, it’s ridiculous. Virtually everything would have to be turned over to wind energy. We would have instead of a war economy a wind economy, where wind energy powers primarily the maintenance of wind power. And we’d still need backup generators!
H.G. Wells wrote, in 1897, “A Story of the Days to Come”:
And all over the countryside, he knew, on every crest and hill, where once the hedges had interlaced, and cottages, churches, inns, and farmhouses had nestled among their trees, wind wheels similar to those he saw and bearing like vast advertisements, gaunt and distinctive symbols of the new age, cast their whirling shadows and stored incessantly the energy that flowed away incessantly through all the arteries of the city. ... The great circular shapes of complaining wind-wheels blotted out the heavens ...In that story, it is indeed the power company that is in power.
That said, it is a fact that wind turbines are being and will continue to be built, so like National Wind Watch I strongly support effective setbacks (at least 2 km, perhaps 5 km) from homes and noise regulations (that limit nighttime indoor noise to 30 dBA, as the WHO recommends, and limit ILFN and pulsating noise as well). And we oppose opening up otherwise protected land to the construction of the giant machines. Of course, such regulation would not contribute to, but instead would threaten, the “success” of wind energy. It would remain rare and unprofitable, as such an absurd source of energy for the modern world should be, used only in the most desperate of circumstances when nothing else is possible and the cost and harm and low benefit might be justifiable.
wind power, wind energy, wind turbines, wind farms, environment, environmentalism