Wind

Wind Power

Contents:

Horizontal Axis Wind Turbines

Vertical Axis Wind Turbines

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Wind has been consistently used in transportation, agriculture and industry for over 3,000 years. Wind power is actually converted solar power. It is caused by solar radiation heating different parts of the earth at different rates. Depending on the time of day and the type of surface, ocean, desert, forest, etc.; solar radiation causes the air to warm. The warm air rises and causes the atmospheric pressure near the earth’s surface to drop. This in turn causes cooler air to be drawn into the low pressure zone resulting from the rising warm air. The air coming from a cooler high pressure zone to a warmer low pressure zone is what we call wind.

Though wind power is still very popular for recreational boating and other traditional uses. It is the generation of electricity through the use of wind turbines which interests us. However, as most people know, wind can be very unpredictable. It follows that the most important aspect of installing a Wind Turbine is. . .

Location, location, location – if ever location was important for the success of an enterprise, it definitely is important for the success of a Wind Turbine. Because of the unpredictability of wind, it is critically important to locate wind turbines in areas that have been surveyed and tested over a period of time to have sufficient wind available. It is also critically important to locate Wind Turbines away from trees and structures which might cause wind turbulence. Please also remember that when using wind maps that show annual averages, wind can have major seasonal changes. Use seasonal maps if possible to confirm wind is availability when you need it. Expecially, if the wind turbine is intended for off grid use.

Wind Turbines are manufactured in a variety of sizes from those that serve a single family to those that can power a good size neighborhood. However, due to the unpredictability of the wind, Turbines normally cannot operate at full capacity all the time. In fact, even though most turbines operate at least 65 to 90% of the time; they operate at far less than their ultimate design capacity. On an annual basis, Wind Turbines yield about 1/3rd of their maximum capacity. Not to worry though, remember compared to other forms of electrical generation which might use fossil fuels and operate at a much higher rate of capacity, wind is free. Moreover, Wind Turbines could be designed to have a higher capacity rate by under sizing the generator and/or over sizing the rotor. But such a design would on an annual basis produce far less electricity.

Therefore, in comparing wind turbines to other forms of electrical generation one must be very aware of the limitations of wind turbines. As a primary source of electricity, Wind Turbines should not be the first choice. However, as a secondary source of energy, Wind Turbines can play a very important role in supplementing the primary source of electricity. When connected to the grid they can be very economical. If the wind turbine is designed in such a way to supply the grid when activated, they can make up for the times they are inoperable due to the lack of wind.

Essentially, there are two types of wind turbines, Horizontal Axis Wind Turbines (HAWTs) and Vertical Axis Wind Turbines (VAWTs). Horizontal Wind Turbines are more common. Nearly everyone is familiar with their appearance. Vertical Axis Turbines are less common and they come in a variety of different designs. The most common of these is the “Egg Beater Design” illustrated below.

Two Examples of Wind Turbines

Want to learn more about wind power in general?:

US Department of Energy / Wind Energy Basics

http://www1.eere.energy.gov/windandhydro/wind_basics.html

AWEA Wind Tutorial

http://www.awea.org/faq/

Wikipedia / Wind Power

http://en.wikipedia.org/wiki/Wind_energy

Wikipedia / Wind Turbine

http://en.wikipedia.org/wiki/Wind_Turbine

United States Energy Maps

http://www.windpoweringamerica.gov/wind_maps.asp

California Energy Maps

http://www.energy.ca.gov/maps/wind.html

* Visit our Planning Tools Section for Informaiton on how to choose the right alternative energy system, how to hire contractors, and Do-it-yourselfer tips and instructions.

Horizontal Axis Wind Turbines

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Horizontal Axis Wind Turbines (HAWTs) can generate electricity at relatively low wind speeds. They range in size from the micro wind turbines whose rotors are from 1.75 meters to 4 meters to huge commercial wind turbines whose rotors measure in excess of 90 meters in diameter. They are always mounted on a tower or supporting structure to elevate the rotor. Generally in order to operate most HAWTs must face the wind. For smaller HAWTs this can be accomplished by providing a tail. For larger HAWTs a control system and motor is used to rotate the turbine.

They are always mounted on a tower or supporting structure to elevate the rotor. As the direction of the wind changes the rotor and generator housing swivels atop the tower to face the wind. It should be noted to operate effectively HAWTs should be installed on towers high enough to avoid wind turbulence caused by nearby trees and structures. One of the main advantages of placing HAWTs off shore is not only to take advantage of the nearly constant breezes but also due to the fact that there is very little turbulence.

Pros:

No pollutant byproducts

Electrical generation is immune from brown outs

Wind Generators can be scaled up from a size appropriate for one family to large commercial sizes that can serve 550 families.

Energy Source is free once initial investment is paid off

Cons:

Has a negative visual impact to many people

Must be mounted on a high pole or tower away from trees and buildings to limit wind turbulence

Susceptible to damage from lighting especially in areas where thunderstorms are frequent

Birds can be injured or killed if they attempt to fly between the turbine blades when in operation

Some turbines can produce a significant amount of noise

Sufficient wind might not be available when needed

Not a good primary source of electricity but can be an excellent secondary source of power if it can be connected to the utility grid

Want to lear more about Horizontal Axis Wind Turbines:

The Encyclopedia of Alternative Energy and Sustainable Living

http://www.daviddarling.info/encyclopedia/H/AE_horizontal-axis_wind_turbine.html

Wind Turbines Now / Horizontal Axis Wind Turbines

http://www.windturbinesnow.com/horizontalaxis-windturbines.htm

Bornay / HAWT manufacturer

http://www.bornay.com/indexe.html

* Visit our Planning Tools Section for Informaiton on how to choose the right alternative energy system, how to hire contractors, and Do-it-yourselfer tips and instructions.

Vertical Axis Wind Turbines

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Vertical Axis Wind Turbines (VAWTs) are unique in that they are not sensitive to wind direction. They also tend to be less sensitive to wind turbulence. They are remarkably quite and are considered more aesthetically pleasing. Because of these advantages they can be installed on the roofs of buildings and are considered well suited for urban environments. However, most VAWTs are not as efficient as HAWTs in harnessing wind energy as they require a relatively high wind speed to start rotation. Nevertheless, recent innovations such as maglift technology are being introduced to eliminate friction thereby lowering the VAWT’s rotor resistance to wind speed. Though many of these innovations still need to prove out over time, they appear very promising. In fact, in the near future it is not unreasonable to expect buildings to be sited and designed to maximize the potential for VAWTs.

Pros: