What is Wind?

Wind is a by-product of solar energy, caused by uneven heating and cooling of the earth’s surface. Low-pressure zones are created where the warmer air rises and pulls in cooler air. Geographical features such as hills, valleys, trees, buildings and lakes directly affect velocity and Wind flow. Seasonal weather patterns and the spin of the planet are also issues that directly affect wind velocity and wind flow.

Wind as an Alternative Energy Source

Wind is a renewable source of clean and sustainable energy. Two of the best features are that it is freely available and secure. Wind is readily available in most areas but is best along coastlines and on hills. The performance of wind is directly affected by seasonal patterns, best performance is during the winter months and worst performance is during the summer months.

A wind turbine is needed to convert wind energy into an energy (electricity) that we can use. The blades of a wind turbine catch the wind and cause the rotor to turn. As a result, this turning drives a generator that converts the wind energy into electricity. Generally speaking, wind energy should be consumed as it is produced; however it is possible to store excess energy using batteries.

Darrieus vs. Savonius vs. Horizontal Wind Turbines

Darrieus, Propeller type and Savonius are three different implementations of wind turbines. The Propeller type wind turbine is what is considered a Horizontal Axis Wind Turbine (HAWT) where the propeller rotates about a horizontal axis. The Darrieus and Savonius designs are a Vertical Axis Wind Turbine (VAWT) where they rotate about a vertical axis.

Darrieus (VAWT – Lift Force):

The shape of the Darrieus is comparable to that of an egg beater, it requires a lift force in order for it to rotate and during rotation, creates an imagery of an egg beater. This type of design does not require the turbine to be turned to face the wind because it can accept wind from all different directions because of the design. The main mechanical features of this turbine such as the powertrain, generator and controls are located near ground level and make it easier to maintain. The Darrieus design causes less electromagnetic interference than the conventional propeller type design. The Darrieus requires an induction motor because it is normally not self starting, the induction motor is used for the initial few revolutions to get the Darrieus to start moving. There is also a rather high tendency for failures and accidents in which the speed of rotations could not be controlled and hence leading to the collapse of the entire structure.

Propeller (HAWT – Lift Force):

The propeller type turbine is similar in appearance to a propeller on an airplane. It requires a lift force in order for it to rotate about a horizontal axis. A utility size propeller type turbine requires constant monitoring of the velocity of wind and direction of wind in order to fully utilize the full force of the wind. The utility sized propeller type requires a motorized mechanism with which will rotate the turbine into the direction of the wind and exploit the full potential provided by the current wind situation. For small wind turbines, a Tail Vane is needed to do the job. The most common material of which the propeller comprises of is fiberglass, one definite shortcoming of fiberglass is that it cannot withstand the stress of rotating at very high speed when the velocity of the wind is high enough. Brakes are also required to avoid overloading of the generator as its operating range cannot be exceeded. As compared with the vertical designs, this horizontal device has most of its mechanisms up by the propeller and depending on the size of tower used, it can be a big task to service these machines. The propeller is required to be raised off the ground about 150-300 feet for the big ones and 50-120 feet for the small ones which is a lot more than is required for a vertical axis turbine, this is in order to avoid turbulent winds generated by other structures closer to the ground, turbulence can severely damage a propeller and mechanisms connected to it which would be very expensive to replace. This type of wind generator should be mounted at least 20 feet higher than any nearby obstructions (300 feet away) to avoid turbulent conditions. Typical Customers for small wind turbines have at least 1 acre of property. An estimated 65% of the US has sufficient wind resources to sustain a Small Wind Turbine. The suggested requirement of wind to sustain a Small Wind Turbine is Class 3 winds and higher.

Savonius (VAWT – Drag Force):

The Savonius type of turbine is the type that Zephyr has based its design around. The Savonius type requires a drag force in order for it to rotate about its vertical axis. Savonius type turbines are resistant to Turbulence and can be mounted closer to the ground, they also do not require shifting or rotating of the turbine in order to utilize the full potential of the wind. The Savonius type turbine has an efficiency nearly as good as the propeller type and Darrieus type turbines, the efficiency like all other designs are dependent upon how well engineered the turbine is. The Savonius type also causes less electromagnetic interference when compared with the propeller type turbines.

Net Metering:

For power consumers located within the supply grid, electricity will always have to be purchased from the utility company at retail price. Recent legislation made net metering a federal policy in all of the United States – owners of wind power generators can sell electricity back to the utilities at the same rate as their purchases” which improves economic return to users significantly. Most of the installations are based on economic payback, in addition to interest in being good environmental citizens.

Net metering is a method for customers with renewable energy generating facilities to sell their electricity back to the utility company. Net Metering meters the production and usage of energy at the facility. Electricity usage metered will be offset by the electricity produced with their wind turbine, it will spin the existing utility meter backwards which will in turn provide the consumer with retail value of the electricity produced by their wind turbine, this is performed until the bill is zeroed. In numerous states, if the electricity produced by the customer is more than their usage during the billing period, the excess energy is credited back to the user at the wholesale rate, this credit can be used during future billing periods. In the United States, net metering is now federally legislated but each of states may have varied policies regarding net metering.

Importance of Net Metering:

  • When electricity is generated by a renewable generation facility, the electricity generated is an intermittent resource and can’t always be used when it is generating.
  • There is a reduced installation cost as a single meter is all that is required for the usage of net metering.
  • Simple system encourages the use of small scale wind and solar energy systems.
  • Credited at retail rate helps financial payback.

Environmental Hazard Issues:

Environmental hazard issues associated with traditional methods of generating electricity (such as using Fossil fuel and Nuclear power plants) can exert a range of impact on air, water and land.

Climate Change:

Problems arise such as global climate changes. Burning of fossil fuels (such as coal, oil and natural gas) releases carbon in the fossil fuels and is then transformed into CO2 which is the predominant gas contributing to greenhouse effects. Greenhouse effect allows energy from the sun to pass thru the Earth’s atmosphere and traps it in the form of heat. It raises the average global temperatures at an accelerated pace which can causes concerns such as:

  • Human health: increased infectious disease caused by nurturing the spread of disease carrying mosquitoes and rodents.
  • Extreme weather impacts: increased frequency of severe heat waves.
  • Coastal Zone and Small island flooding: once global temperature raises, sea level will rise. This will cause rising sea levels and severe ocean storms.
  • Forest Devastation: since trees and vegetation are slow to respond to climate cycles, they may be unable to survive due to unpredictable weather.
  • Agriculture: changing weather patterns associated with changing global climate patterns pose major threats for farmers.

Acid Rain:

Acid rain is a term used to describe rain, mist or snow that is more acidic than usual. Normal rainwater has a pH of approximately 5.6 whereas acid rain has a pH of about 4.4. Burning fossil fuels emits two different ingredients such as SO2 and NOx, when these ingredients are combined with moisture these pollutants return to the earth as acids. Acid rain is accountable for the disappearance of several marine species, mortality and slow growth of a several tree species, corrosion of metals and deterioration of paint/stone and reduced visibility due to SO2/NOx emissions.


The Ozone layer provides a layer of protection from the ultraviolet rays of the sun. The burning of fossil fuels emits NOx and when combined with volatile organic compounds, creates ozone pollution and that in turn creates urban smog (a form of Ground Level Ozone). Ground level ozone can cause respiratory problems, allergic reactions and visual problems in humans. It also interferes with plants’ ability to turn sunlight into usable energy.

Pollution of Water:

Due to routine operations and power plant machinery maintenance, certain procedures will pollute bodies of water. Different procedures are used to clean and cool the machinery, these procedures emit impurities into the water that washes them and is then washed into the sewage system. Pollutants such as copper, iron, nickel and cleansing chemicals are mixed into the water during routine operations/maintenance, these contaminants are hard to remove from water and are devastating to the environment.

Power plant premises and surrounding area Land Impacts:

On Premise:

The life expectancy of a nuclear power plant is about 40 years. During the life of a nuclear power plant, electricity generators tend to leave their land scarred and polluted due to the waste produced by the usage and maintenance of the generators. There will be a major reduction in the value of land during the years of operation of the power plant. Due to the land being contaminated by toxic residues and pollutants during the operation of the power plant, even after the power plant has been put out of commission, the piece of land which once occupied by the power plant and surrounding area can no longer be used as a site for future development due to hazardous living conditions.

Surrounding area:

Most electricity generation facilities also generate waste by-products which is a toxic substance, the waste is usually sent off to a landfill at a remote location and therefore the pollutants reach a far greater distance than just the premises of the power plant. The waste if not stored properly may leak and reach underground water sources which will contaminate the once pure water source. The mining of coal erodes hills and mountains, leaving a visually unattractive sight to visitors of the area. Natural gas piping across landscapes disrupts wildlife habitat, violates private land premises and eliminates the use of the land for other uses.

Benefits of using small wind turbine:

How much savings per bill?

Depending on the installation, most owners expect anywhere from 50%-90% savings per electric bill.

How long does it take to pay off cost of wind turbine in the United States?

It takes approximately 6 to 15 years to pay off the cost of the wind turbine, the variance is dependent mostly on the location of the installation. Variations in the incentives and cost of electricity due to different state regulations lead to a difference in the length it takes to pay off the cost of a wind turbine.

How much of an impact does a wind turbine help in terms of the environment?

1.2 tons of air pollutants and 200 tons of greenhouse gases will be generated by burning fossil fuels during the lifetime of a wind turbine. A small wind turbine produces no pollution at all, hence it is a zero emission generator.

What government incentives are there to owning a small wind turbine?

For US residents, there are incentives given by the government dependent on the area where you reside. Refer to the link to find your location: Database of State Incentives for Renewable Energy

Popular Misconceptions about Wind and Solar Power [1]

The following are common misconceptions about wind power:

i. Shadow “Flicker”

  • Depends on the time of day, day of year, and latitude of the site’s location.
  • Typically the result of low rotating speeds.
  • Turbines of all sizes are designed to start spinning only after a minimum wind speed has been attained, so chances are very slim that a small turbine will spin slowly enough to make shadow flicker a concern.
  • Normal setback distances dictated by property lines or sound requirements mitigates, if not entirely eliminates, this potential nuisance, especially at U.S. latitudes. 

 ii. Attractive Nuisance

  • Windmill towers pose no more of an “attractive nuisance” than any other pole or tower in the neighborhood, including water towers, cell phone towers, etc.
  • In most cases a potential climber would first have to trespass on private property – a much more prevalent issue and one that should be dealt with separately.
  • Some wind turbine tower designs have no available hand- or footholds so they simply can’t be climbed.

 iii. Birds

  • The most common – and most exaggerated – misconception about both large and small turbines is that they are disproportionately harmful to bird and bat populations.
  • Utility-scale wind farms that are grouped closely in large arrays account for less than 0.003% of all human-caused bird deaths. No data exists for small wind, but it can be inferred to be less. House cats and glass windows, by comparison, cause 10,000 times more bird deaths than do wind turbines.
  • Environmental impact or avian migration studies should not be required for individual small wind turbine installations.
  • Small wind turbines in fact offer a net benefit to local and global environments: they emit no air pollutants, require neither mining for fuel nor water for cooling, and have land use “footprints” of only a few square feet.

 iv. “Icing”

  • Unlike tree branches, wind turbine blades are designed to withstand a heavy load of ice. When ice builds up on the blades, they simply don’t “fly” any more – they lose their aerodynamic properties. There is no danger of ice being “thrown” off.
  • Typically, the ice melts and falls – straight down – to the base of the tower.
  • A 1998 study calculated that the risk of personal or property damage from ice falling from a (large) turbine is lower than the risk of being struck by lightning.

v. Noise Pollution

  • Most residential-sized wind generators have few moving parts and unlike the utility-scale turbines used in wind farms, which are isolated from other human development.
  • Most of the sound from a residential sized wind turbine is aerodynamic noise; modern residential turbines measure the same, or close to the ambient noise levels under most wind conditions.
  • Most residential turbines do not begin turning until a certain threshold, or “cut-in” wind-speed is reached, so on a calm, windless day (or night), the turbines are still and silent.

 vi. Electrical Signal Interference

  • Small wind turbine blades are made from materials that are “invisible” to radio frequency transmissions and cannot cause interference problems.
  • In the past, wind turbine blades were sometimes made of metal which did create unwanted radio or television interference, but the industry has long since abandoned the use of metal blades.
  • Any structure under 200 feet high – that is to say, any small wind turbine – is also too short to interfere with civilian or military radar. Radar usually does not even scan for objects this close to the ground because common land features at this height, like trees, would normally cause distorted, cluttered, or misleading radar images.

 vii. Lightning Strikes

  • Small wind turbines are “grounded,” meaning that any static electricity on the tower or generator is dispersed into the ground, preventing a build-up that could invite lightning strikes.
  • Small wind turbines incorporate back-up technologies like surge and lightning arrestors (also known as silicon oxide varistors) and metal oxide varistors, which are also used to protect home computers from electrical surges.
  • Lightning strikes are never completely preventable, but these industry standard measures offer the best protection available to the owner of the wind system. Good practice in the wind industry includes grounding of all towers and guy wires, which significantly reduces the chance of a lightning strike.

 viii. Stray Voltage

  • Results from faulty wiring on any number of electrical systems (not just wind turbines) and easily prevented by industry-standard practices.
  • Strictly localized issue that will not affect off-site parties or properties.
  • While the design of electrical system makes stray voltage possible, its actual occurrence is the result of poor grounding practices, improper or inadequate wiring, or deteriorated wire insulation.
  • Most small wind turbine inverters – those that are IEEE 1547 or UL1741 compliant – can detect faulty grounding and automatically shut down current flow. Like solar photovoltaic installations that require “ground-fault circuit interrupter” (GFCI) devices to protect consumers from any stray voltage, small wind turbines are also equipped with GFCI measures.

[1] Source: The American Wind Energy Association (AWEA)

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