Wind Farms Cause More Environmental Impact Than Previously Thought

When it comes to energy production, there’s no such thing as a free lunch, unfortunately.

As the world begins its large-scale transition toward low-carbon energy sources, it is vital that the pros and cons of each type are well understood and the environmental impacts of renewable energy, small as they may be in comparison to coal and gas, are considered.

In two papers — published today in the journals Environmental Research Letters and Joule — Harvard University researchers find that the transition to wind or solar power in the U.S. would require five to 20 times more land than previously thought, and, if such large-scale wind farms were built, would warm average surface temperatures over the continental U.S. by 0.24 degrees Celsius.

“Wind beats coal by any environmental measure, but that doesn’t mean that its impacts are negligible,” said David Keith, the Gordon McKay Professor of Applied Physics at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and senior author of the papers. “We must quickly transition away from fossil fuels to stop carbon emissions. In doing so, we must make choices between various low-carbon technologies, all of which have some social and environmental impacts.”

Keith is also professor of public policy at the Harvard Kennedy School.

One of the first steps to understanding the environmental impact of renewable technologies is to understand how much land would be required to meet future U.S. energy demands. Even starting with today’s energy demands, the land area and associated power densities required have long been debated by energy experts.

In previous research, Keith and co-authors modeled the generating capacity of large-scale wind farms and concluded that real-world wind power generation had been overestimated because they neglected to accurately account for the interactions between turbines and the atmosphere.

In 2013 research, Keith described how each wind turbine creates a “wind shadow” behind it where air has been slowed down by the turbine’s blades. Today’s commercial-scale wind farms carefully space turbines to reduce the impact of these wind shadows, but given the expectation that wind farms will continue to expand as demand for wind-derived electricity increases, interactions and associated climatic impacts cannot be avoided.

What was missing from this previous research, however, were observations to support the modeling. Then, a few months ago, the U.S. Geological Survey released the locations of 57,636 wind turbines around the U.S. Using this data set, in combination with several other U.S. government databases, Keith and postdoctoral fellow Lee Miller were able to quantify the power density of 411 wind farms and 1,150 solar photovoltaic plants operating in the U.S. during 2016.

“For wind, we found that the average power density — meaning the rate of energy generation divided by the encompassing area of the wind plant — was up to 100 times lower than estimates by some leading energy experts,” said Miller, who is the first author of both papers. “Most of these estimates failed to consider the turbine-atmosphere interaction. For an isolated wind turbine, interactions are not important at all, but once the wind farms are more than five to 10 kilometers deep, these interactions have a major impact on the power density.”

The observation-based wind power densities are also much lower than important estimates from the U.S. Department of Energy and the Intergovernmental Panel on Climate Change.

For solar energy, the average power density (measured in watts per meter squared) is 10 times higher than wind power, but also much lower than estimates by leading energy experts.

This research suggests that not only will wind farms require more land to hit the proposed renewable energy targets but also, at such a large scale, would become an active player in the climate system.

The next question, as explored in the journal Joule, was how such large-scale wind farms would impact the climate system.

To estimate the impacts of wind power, Keith and Miller established a baseline for the 2012‒2014 U.S. climate using a standard weather-forecasting model. Then, they covered one-third of the continental U.S. with enough wind turbines to meet present-day U.S. electricity demand. The researchers found this scenario would warm the surface temperature of the continental U.S. by 0.24 degrees Celsius, with the largest changes occurring at night when surface temperatures increased by up to 1.5 degrees. This warming is the result of wind turbines actively mixing the atmosphere near the ground and aloft while simultaneously extracting from the atmosphere’s motion.

This research supports more than 10 other studies that observed warming near operational U.S. wind farms. Miller and Keith compared their simulations to satellite-based observational studies in North Texas and found roughly consistent temperature increases.

Miller and Keith are quick to point out the unlikeliness of the U.S. generating as much wind power as they simulate in their scenario, but localized warming occurs in even smaller projections. The follow-on question is then to understand when the growing benefits of reducing emissions are roughly equal to the near-instantaneous impacts of wind power.

The Harvard researchers found that the warming effect of wind turbines in the continental U.S. was actually larger than the effect of reduced emissions for the first century of its operation. This is because the warming effect is predominantly local to the wind farm, while greenhouse gas concentrations must be reduced globally before the benefits are realized.

Miller and Keith repeated the calculation for solar power and found that its climate impacts were about 10 times smaller than wind’s.

“The direct climate impacts of wind power are instant, while the benefits of reduced emissions accumulate slowly,” said Keith. “If your perspective is the next 10 years, wind power actually has — in some respects — more climate impact than coal or gas. If your perspective is the next thousand years, then wind power has enormously less climatic impact than coal or gas.

“The work should not be seen as a fundamental critique of wind power,” he said. “Some of wind’s climate impacts will be beneficial — several global studies show that wind power cools polar regions. Rather, the work should be seen as a first step in getting more serious about assessing these impacts for all renewables. Our hope is that our study, combined with the recent direct observations, marks a turning point where wind power’s climatic impacts begin to receive serious consideration in strategic decisions about decarbonizing the energy system.”


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    • Assessing the impact of windfarms requires that all wind based latent heat be analyzed globally (whether or not there are windfarms). As I understand it, virtually all wind is eventually converted to heat due to the 2nd law of thermodynamics. Windfarms may raise local temperatures and there are bound to be environmental effects due to increased temperatures close to windfarms as well as the reduction of air speeds downstream. However, the heat released by a windfarm is likely to have a minimal effect on global temperatures because wind energy is converted to heat eventually, regardless.

  • In my view the Harvard study is not worth the paper it is published on. It raises serious questions what Harvard is up to receiving millions from the global climate deniers Koch brothers. It is a serious setback to Harvard's credibility and causes damage Harvard's reputation.

    The study reports a huge number of turbines disturbing the airflow without reporting the GWh it would generate that would displace all thermal electricity from fossil fuels and nuclear. Whatever local warming would be caused by wind turbines in this theoretical exercise it would be many orders of magnitude LESS than thermal load ro the immediate environment from generation of an equal amount of GWh of electricity from dirty fossil fuels and nuclear that would be displaced by clean wind electricity.

    Measuring local thermal load from wind power generation from wind without factoring the averted local thermal load from the displaced fossil fuels and nuclear is frankly ludicrous.

    Of course fossil fuels not only emit MUCH BIGGER local thermal loads (a single coal power plan in Massachusetts local thermal load eliminated 87% of the winter flounder in Mt Hope Bay) but also:
    1) emit toxic pollution causing autism from mercury (no vaccines do not cause autism coal power plants do
    2) emit tons of SO2 and other greenhouses gases causing global climate change.

    So give me clean wind power any day over the alternative dirty electricity. We can NOT compare the impact of wind power as if the alternative was not no electricity. In fact there the threat from local warming would be reduced.

  • In my opinion. These windmills are a highly subsidized blight on the landscape that absolutely slaughter migrating birds by the thousands. With no regulations to stop them during peak migrations.I believe it we will see a decline in all raptors,such as the eagles had with DDT before the greenies wake up and see this is not a panacea.

  • Dear Brownie (is this we call the likes of coal-lovers like Trump?),

    The only way to write what you write is to be anti-science. I deconstruct your comment referencing science:

    1) "highly subsidized" = true in 1985. Already false in 2005 if you factor-in medical costs from dirty fossil fuels. According to the US Army Corps of Engineers detailed analysis for the Cape Wing proposal the cost from doctors, hospitals, pharmacies, lost work and premature death came to $53,000,000 for displacing 1,500,000 MWh to be displaced by clean wind power a year. Do the math and you will see it comes to $0.037/KWh compared to the $0.024/KWh of the tax break that some called subsidy (but refused to call such tax breaks subsidies). This medical cost did not include hard to measure damage like retardation of fetus and autism from mercury from coal in air pollution.

    2) "the blight on the landscape" most people love the looks of turbines. In study after study most people do not care how turbines (or anything looks) but for those you care for every 10 who love the looks only one hates their looks. Some of those who hate the looks have bizarre reactions such they see them of giant spiders. Those who love their looks have described them as elegant ballerinas leaping in the sky and complained if something happens to block the beautiful view of a wind turbine turning in the distance. Interestingly half of those who hate their looks still support them for environmental or economic benefit.

    3) "slaughter migrating birds by the thousands. With no regulations to stop them during peak migrations." 6 years of studies in Denmark with radar sensitive enough to detect a moth by day or night tracked million of birds flying over, through or around turbines wind turbines. Between 200 and 100 yards most birds engaged in avoidance behavior. Due to the vibrations birds sense and respond avoiding wind turbines faster than ANY other man made or natural obstacle. There have been reports of thousand of migrating birds piling up in the dark on a single chimney or building, never on wind turbine. Collisions with a modern gigantic modern turbine is extremely rare and unlikely event. Please stop the scientific proven lies.

    4) "I believe it we will see a decline in all raptors,such as the eagles had with DDT" The truth about raptors comes about a few hundred birds killed at Altamont Pass in California where small fast turning 1985 wind turbines birds could not see them perched on the trushes supporting them, and run into the fast turning blades. The modern turbine on monopoles have no place for raptors to pearch, turn slowly birds can see them, and turn their blades above the bird fly zone. The Center for Biodiversity (greenies as you call them) that reported the loss of a few birds of these endangered species at Altamont Pass proposed "repowering" as a solution. This means replacing little dangerous turbines with big modern turbines that are safe for birds as a solution. A modern turbine makes more electricity than 100 old ones. Also locating with knowledge of the potential problem created safe for raptors environment. DDT still kills today decades after it was banned.

    On the other hand fossil fuels cause local bird extinctions near fossil power plants in a number of ways. SO2 and Ozone that cause childhood asthma, bronchitis, cancer, and heart disease in humans also heart birds that have more sensitive lungs. Song bird have been wiped when acid rain bleach calcium from the soil and killed snails critical for birds to lay eggs with hard shell. Soft eggs so not hutch. Mercury a neurotoxin, made loons too fidgety to roost and their eggs did not hatch in areas of the Great Lakes poisoned from fossil fuel air pollution. Scientific conclusion wind turbines save bird lives.

    The lies and misinformation will not save the dirty fossil fuel economy. Do you have any more wrong information to change the conversation about the ludicrous new false information propagated by the Harvard study. Yes turbines have measurable impact on the environment but it is a net benefit compared with the impact of electricity generated with fossil fuels as an alternative.

    • "2) “the blight on the landscape” most people love the looks of turbines. In study after study most people do not care how turbines (or anything looks) but for those you care for every 10 who love the looks only one hates their looks."

      I doubt that claim in full context (industry-funded study or non-existent). Even if partly true, "most people" lost considerable respect for nature long ago, becoming obsessed with money as the real "green" they seek. The views of "most people" tend to be shallow and materialistic. Look at what mining and logging has done to landscapes, for example. Some will protest it but most prefer the upsides. Wind turbines are like inverse logging, planting super-sized dead tree skeletons with red lights to boot.

      Environmentalists have tried to save landscapes from much smaller cellphone towers and ski lifts, so it makes no sense that deriving energy from monster machines would wipe out those concerns. But I'm sure, some Greens have been feigning eco-concerns all along, which brings us full circle to excuses for Big Wind.

      Your other standard excuses are covered here: "Industrial Wind Turbines and the Rationalized Desecration of Nature"

  • Prior to the late 1800's, Earth really did not have a stable, fixed-position, reliable source of electricity. Since then, Mankind has provided enormous amounts of electricity - primarily for his own consumption, but almost certainly to the benefit of some narrow ranges of microorganisms.

    I am going to propose that we are providing an extremely stable, easily accessible resource in the form of electrical networks and that we live in an environment were microorganisms seem readily able to adapt to take advantage of such a steady supply of energy. As such, the potential exists for us to be fueling forms of life that are foreign and otherwise detrimental to the small building blocks of life on which we ultimately depend.

    In the past we've leaded our gasoline with heavily marketed Ethyanol, polluted our oceans with loose nuclear waste since it was inexpensive in the short-term, and we have believed that cigarettes have health benefits. Most of this is ultimately the downside of unbridled greed which is a motivating power of capitalism. Perhaps we should stop getting focused on the issues that are presented to us and really start looking for the problems that are going to destroy us. If there is a fundamental problem with electricity, and I have just outlined a slightly reasonable scenario, neither side has much of a reason to make us aware of something fundamentally wrong while they jockey to improve earnings.

    • "Prior to the late 1800’s, Earth really did not have a stable, fixed-position, reliable source of electricity."

      BUT world population in the 1800 was about one billion, now it is over 7.5. No going back to one billion.

      We need clean renewable electricity now. Capitalism is evil only when it concentrates power into monopolies. With renewable energy energy production will be decentralised and capitalism will be democratized. This is one more benefit or clean local renewable sources of energy. Coal and oil are not only ugly, dirty, and disease causing but also necessitate concentration of capital that results in totalitarian theocratic societies like Saudi Arabia, Texas, and Russia.

  • Earth really did not have a stable, fixed-position, reliable source of electricity bask in the 1800, but is also had only one billion population, now it is over 7.5. There is no going back to one billion.

    We need clean renewable electricity now.

    Capitalism is evil only when it concentrates power into monopolies. With renewable energy energy production will be decentralised and capitalism will be democratized. This is one more benefit or clean local renewable sources of energy. Coal and oil are not only ugly, dirty, and disease causing but also necessitate concentration of capital that results in totalitarian theocratic societies like Saudi Arabia, Texas, and Russia.

  • This article is a rather misleading report on a study of the impacts of wind turbines. They distribute air that leads to localized temperature changes. They do NOT increase temperatures globally like fossil fuels do! Every form of generating energy has some environmental impact, but energy efficiency and renewable energies are the best way to fight climate change (the study authors acknowledge this). Wind energy has been used for thousands of years, it is proven, carbon-free energy with one of the lowest overall environmental impacts of any electricity source. See also:

  • How do obvious incompetents get published?
    They forecast that wind turbines would increase surface temperatures, how is that possible when the 33-66% of waste heat from all the fuelled power plants in the USA has been eliminated?

  • Infrasound plus low frequency noise cause big health problems for people and animals who live near wind turbines.

    They slice and dice thousands upon thousands of bats and birds.

Leah Burrows, SEAS Communications

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