Windmills vs birds and bats

by Sandra Van Berkel

cute bird pictureClimate change-induced extinctions are likely to threaten one in six species if steps aren’t taken to reduce carbon emissions. [1] Since alternative energy reduces carbon emissions, wind turbines will ultimately save birds.

In 2015, Prof Mark Urban from the University of Connecticut reviewed the results of 131 studies on extinction risk to give a global picture of the risks posed by climate change.

The study predicts that as many as 16% of all plant and animal species would be under threat of extinction with four degrees of global warming. [2] With only two degrees of global warming, a report presented by the WWF Global predicts that bird extinction rates could be as high as 38% in Europe and 72% in NE Australia. [3] According to a study published September 2, 2015 in the open-access journal PLOS ONE by Gary Langham and colleagues from the National Audubon Society, over 50% of nearly 600 surveyed bird species may lose more than half of their current geographic range across three climate change scenarios through the end of the century in North America. [4]

Heavy U.S. dependence on foreign oil and increased environmental damage from coal and gas-derived power have stimulated the development of alternative sources of energy production. Because wind power costs less than coal and nuclear power and contributes almost no pollutants to the environment, wind turbines are a viable alternative power source and part of a solution to our global warming problem.

Unfortunately, some people are fighting against massive wind turbines because of reported bird mortality rates at large wind farms. However, research shows that large wind turbines kill relatively few birds compared to other anthropogenic sources and man-made structures. [5]

Proximate causes of bird fatalitiesAlthough bird fatalities have been reported at all large wind energy facilities, newer wind turbine technology has reduced rates of collisions compared to older turbine technology. Because of this, there are a growing number of endorsements by conservation groups. For instance, the American Bird Conservancy supports wind power with newer, bird-friendly designs. [6] The Wisconsin Bird Initiative concedes that wind turbines are low-impact on bird populations compared to window glass and communication towers. [7] And the Audubon Society’s president is quoted by Renewable Energy World as stating, “When you look at a wind turbine, you can find the bird carcasses and count them. With a coal-fired power plant, you can't count the carcasses, but it's going to kill a lot more birds." [8]

Although the AWWI reported this year that the current estimates of wind-farm fatalities do not appear likely to lead to population declines in most bird species [9], the majority of wind-farm related fatalities are migrating bats. ABC News reports that 600,000 bats per year are killed by large wind farms. [10]

The most probable causes of bat fatalities include direct collisions and barotrauma (internal hemorrhaging caused by air pressure differences). [11] Current research suggests that bats are less likely than birds to directly impact spinning blades, but are more likely to suffer barotrauma because their lungs are less rigid and strong than that of birds. [3] As wind moves through large wind turbines, the air pressure drops by 5-10 kilopascals. A wind-farm fatality study conducted in 2007 showed that 90 percent of the 75 bats dissected had been killed by burst blood vessels in their lungs. The injuries suggest that barotrauma had killed the bats.[12]

Since little is known about the status of bat populations or the ecological impact of bat fatality levels, conservationists can only suggest that windmill farms should be located away from the migratory flight paths of bats. [12] Because large air pressure drops do not occur with small or micro wind turbines, no study has been found to quantify any possible injuries or fatalities to mammals at or around a small or micro wind turbine sites and therefore there have been no recommendations found as to their use or placement.

Note: The largest cause of bat fatalities are humans who are not cognizant of the dangers of accidentally waking bats from their torpor (sleep) and the fatal effect of White Nose Syndrome (WNS). Sleep disruption from humans and WNS causes huge metabolic disturbances and leads to starvation during the winter months. Since 2006, 5.7-6.7 million bats have succumbed WNS. For more information, please visit

Graph references: [17] [15] [16] [6]

07/23/2019 Note: Unfortunately, a few of the above references are no longer available online. Please contact us if you require more information.

How Wind Power Works

by Sandra Van Berkel

wind technology has been around for a whileImplementing a small wind turbine system for your own needs is one way to guarantee that the energy you use is clean and renewable. But most people don’t understand how wind power works. The wind, the transformation of kinetic energy to electrical energy, blade design, and turbine placement are all important components of capturing wind power efficiently.

The uneven heating of the atmosphere by the sun, irregularities of the earth’s surface, and the rotation of the earth form wind. When the sun heats up an area of land, hot air begins to rise and cooler air flows quickly to fill the gap the hot air left behind. The cooler air rushing in to fill the gap is wind. Wind can be modified by bodies of water, vegetation, and differences in terrain and vary greatly across the U.S.

US Annual Average Wind Spped Wind energy production is the process of capturing the kinetic energy from the wind and transforming it to mechanical or electrical power. Wind turbines transfer energy from one medium to another. Air is a gas that contains particles. Moving particles in the wind have kinetic energy. The particles push the turbine blades and cause them to move.

The kinetic energy in wind increases exponentially in proportion to its speed. A small increase in wind speed equates to a large increase in power production potential. In theory, doubling wind speed will produce an eight-fold increase in power production. This is theoretical because the Betz limit states that only 59% of wind energy can be captured. However, a small increase in wind speed still produces a significant increase in power output.

diagram of rotor and statorTurbine blades spin a shaft that leads from the hub of a rotor to an alternator. The alternator converts the rotational energy into electricity using electromagnetic induction. A very simple alternator consists of a magnet and conductor. The rotor consists of permanent magnets affixed to a shaft and surrounded by coiled wires (the stator). If you have spinning magnets surrounded by coils, one part is rotating relative to the other and the system will induce voltage. The voltage drives electrical current out through wires for distribution.

Turbine blades are designed to be twisted so they can always present an angle that takes advantage of an ideal lift-to-drag force ratio. A high lift-to-drag ratio is important when designing an efficient turbine blade because a good ratio is what keeps the blades moving with the least resistance.

Blade size is also an important consideration when designing an efficient windmill. The longer the blades, the more energy a turbine can capture from the wind. More energy equates to more electricity-generating capacity. In general, if you double the blade length you will produce four times the energy output. However, in low-wind conditions, a smaller blade size can potentially produce more energy because it will take less wind-power to spin a smaller windmill.

Height is an important component in wind turbine placement. The higher the turbine, the more energy it can capture. Higher elevations also reduce ground friction, which can interrupt the flow of wind created by nearby stationary objects.

REVOLT wind has considered and optimized all of the wind turbine components making it efficient as well as inexpensive. Owning an efficient and inexpensive windmill, like the REVOLT, will generate clean and renewable electrical energy while making it affordable for nearly everyone on the planet.

Comparing costs of Renewable and Conventional Energy

Excerpt by Mitch Tobin

cost of energyIn essence, this analysis offers an apples-to-apples comparison of the costs of financing, building, operating, and maintaining a power plant. The values are expressed in dollars per megawatt-hour.

One of the most widely used levelized cost studies is conducted by Lazard, an international financial advisory and asset management firm. Their latest version of the study, version 8, was released in late 2014. The graphic below summarizes the cost components of 16 different energy technologies evaluated by Lazard: 10 of them are alternative (which includes mainly low-carbon, renewable technologies), and six are conventional (which includes fossil fuel sources and nuclear).

Onshore wind has the lowest average levelized cost in this analysis at $59 per megawatt-hour, and utility-scale photovoltaic plants weren’t far behind at $79. By comparison, the lowest cost conventional technologies were gas combined cycle technologies, averaging $74 per megawatt-hour, and coal plants, averaging $109. These numbers are the average of Lazard’s low- and high-end estimates (see their study for more about their cost calculations).

Looking across the 16 technology types, the 10 alternative technologies cost an average $147 per megawatt-hour, $18 less than the conventional approaches. “Certain Alternative Energy generation technologies,” Lazard wrote, “are cost-competitive with conventional generational technologies under some scenarios.”

By dividing the costs among capital, fuel, and operations and maintenance (O&M), you can see some dramatic differences among the technologies. Many renewable technologies, such as wind, solar, and geothermal, may not be cheap to build, but they have no fuel costs once they’re up and running, and generally have lower O&M costs as well.

Tobin, M. (2015, February 12). Comparing the Costs of Renewable and Conventional Energy Sources

U.S. Federal and State Renewable Energy Incentives

dollar billCurrently, a federal-level investment tax credit (ITC) is available to help consumers purchase small wind turbines for their home, farm, or business (existing buildings and new construction qualify). Owners of small wind systems with 100 kilowatts (kW) of capacity or less can receive a credit for 30% of the total installed cost of the system.

The ITC, written into law through the Emergency Economic Stabilization Act of 2008, is available for equipment installed from October 3, 2008 through December 31, 2016. The value of the credit is now uncapped, through the American Recovery and Reinvestment Act of 2009.

Rapid Depreciation:
Double-declining balance, five-year depreciation schedule (I.R.C. Subtitle A, Ch. 1, Subch. B,Part VI, Sec. 168 (1994) (accelerated cost recovery system)) is another federal policy that encourages wind development by allowing the cost of wind equipment to be depreciated faster.

Please consult your tax professional or find Policies & Incentives by State at

Wind Vision: A New Era for Wind Power in the United States

Wind Vision LogoThe Wind Vision Report, published by the Office of Energy Efficiency & Renewable Energy, considers America’s currently installed wind power capacity across all forms of wind energy (land-based, offshore, and distributed) as its baseline. This capacity that has tripled since the 2008 release of the Energy Department’s 20% Wind Energy by 2030 report. The report assesses the potential economic, environmental, and social benefits of a scenario where U.S. wind power supplies 10% of the nation’s electrical demand in 2020, 20% in 2030, and 35% in 2050. The Wind Vision Report builds upon the continued success of the wind industry to date and quantifies a robust wind energy future.

Key Findings of the Wind Vision Report:

  • Wind energy is available nationwide. The Wind Vision Report shows that wind can be a viable source of renewable electricity in all 50 states by 2050.
  • Wind energy supports a strong domestic supply chain. Wind has the potential to support over 600,000 jobs in manufacturing, installation, maintenance, and supporting services by 2050.
  • Wind energy is affordable. As wind generation agreements typically provide 20-year fixed pricing, the electric utility sector is anticipated to be less sensitive to volatility in natural gas and coal fuel prices with more wind. By reducing national vulnerability to price spikes and supply disruptions with long-term pricing, wind is anticipated to save consumers $280 billion by 2050.
  • Wind energy reduces air pollution emissions. Operating wind energy capacity avoided the emission of over 250,000 metric tons of air pollutants, which include sulfur dioxide, nitric oxide, nitrogen dioxide, and particulate matter, in 2013. By 2050, wind energy could avoid the emission of 12.3 gigatons of greenhouse gases.
  • Wind energy preserves water resources. By 2050, wind energy can save 260 billion gallons of water—the equivalent to roughly 400,000 Olympic-size swimming pools—that would have been used by the electric power sector.
  • Wind energy deployment increases community revenues. Local communities will be able to collect additional tax revenue from land lease payments and property taxes, reaching $3.2 billion annually by 2050.

Comparing Key Features of Renewable Energy Sources

The Revolt Hanging Wind Turbine

REVOLT windmillsIn addition to the advantages listed on the product page, there are other benefits to owning a REVOLT wind turbine. After preliminary testing, we estimate that a 1-meter diameter turbine will produce 5 W in a 10 mph wind and 125 W in a 20 mph wind. That means that you could produce over 100 W of power using an inexpensive device that weighs about 25 pounds. Mass-production will make this turbine so inexpensive that the ‘payback time’ (the time it takes to generate enough electricity to make up for the purchase/installation price) will be comparatively brief.

Depending upon the size and your wind conditions, the REVOLT wind turbine may turn out to be the lowest cost green energy generator ever produced!

Traditional Windmill Designs

traditional windmill designsSmall, tower-mounted wind turbine setups can cost anywhere from several hundred dollars to several hundred-thousand dollars and require land, transmission lines, footers, guide wires, and permits. A large-scale commercial setup costs a lot more! A single, 1.8-MW turbine can run up to $1.5 million installed.

Repairs and maintenance are also expensive and dangerous. Tower-mounted windmills are often damaged by lightening and frequently use inefficient gears that require lubrication. They also require expensive control systems that turn the blades away from heavy wind or reduce the spin rate to avoid damage.

Vertical-Axis Wind Turbines

vertical axis wind turbinesVertical-axis wind turbines represent a significant change in windmill design but are less efficient than traditional turbines and are subject to the same disadvantages. They require high-winds to produce power and are damaged by heavy snow and ice loads.

Solar Panels

solar panelsSolar panels usually need installation permits because they require engineered structural supports that are expensive and immobile. The panels are damaged or lose efficiency when subject to high winds, hail, dust, snow loads, or other debris. They require frequent cleaning to maintain their efficiency and repairs can be expensive and dangerous.