Small wind turbine

File:Wind-power-small-scale.jpg

Small-scale wind power in rural Indiana.

Small wind turbines are wind turbines which have lower energy output than large commercial wind turbines, such as those found in wind farms. These turbines may be as small as a fifty watt generator for boat, caravan, or miniature refrigeration unit. Small units often have direct drive generators, direct current output, aeroelastic blades, lifetime bearings and use a vane to point into the wind. Larger, more costly turbines generally have geared power trains, alternating current output, flaps and are actively pointed into the wind. Direct drive generators and aeroelastic blades for large wind turbines are being researched.

Market

United States

Small wind turbines added a total of 17.3 MW of generating capacity throughout the United States in 2008, according to the American Wind Energy Association (AWEA). That growth equaled a 78% increase in the domestic market for small wind turbines, which are defined as wind turbines with capacities of 100 kW or less. AWEA's "2009 Small Wind Global Market Study", published in late 2009 May, credited the increase in part to greater manufacturing volumes, as the industry was able to attract enough private investment to finance manufacturing plant expansions. It also credited rising electricity prices and greater public awareness of wind technologies for an increase in residential sale. But a poll of small wind manufacturers found that the growth in 2008 might be only a glimmer of things to come, as the companies projected a 30-fold growth in the U.S. small wind market within as little as five years, despite the global recession. The U.S. small wind industry also benefits from the global market, as it controls about half of the global market share. U.S. manufacturers garnered $77 million of the $156 million that was spent throughout the world on small wind turbine installations. A total of 38.7 MW of small wind power capacity was installed globally in 2008.

Installation

To see an animation of a small wind turbine being assembled see Wind Turbine 24v's website

Turbines should be mounted on a suitable tower to raise them above any nearby obstacles. A good rule of thumb is that turbines should be at least 30 feet (9 m) higher than anything within 500 feet (152 m). In general, an effort should be made to make sure that a small wind turbine is as far away as possible from large upwind obstacles. Measurements made in a boundary layer wind tunnel have indicated that significant detrimental effects associated with nearby obstacles can extend up to 80 times the obstacle's height downwind. However, this is an extreme case. Another approach to siting a small turbine is to use a shelter model to predict how nearby obstacles will affect local wind conditions. Models of this type are general and can be applied to any site. They are often developed based on actual wind measurements, and can estimate flow properties such as mean wind speed and turbulence levels at a potential turbine location, taking into account the size, shape, and distance to any nearby obstacles.

A small wind turbine can be installed on a roof. Installation issues then include the strength of the roof, vibration, and the turbulence caused by the roof ledge. Small-scale rooftop turbines suffer from turbulence and rarely generate significant amounts of power, especially in towns and cities.

Types

Smaller scale turbines for residential scale use are available, they are usually approximately 7 to- in diameter and produce electricity at a rate of 300 to 10,000 watts at their tested wind speed. Some units have been designed to be very lightweight in their construction, e.g. 16 kilograms (35 lb), allowing sensitivity to minor wind movements and a rapid response to wind gusts typically found in urban settings and easy mounting much like a television antenna. It is claimed, and a few are certified, as being inaudible even a few feet (about a metre) under the turbine.

Vertical axis wind turbines are a growing type of wind turbine in the small-wind market. These turbines, by being able to take wind from multiple dimensions, are more applicable for use at low heights, on rooftops, and in generally urbanized areas. Their ability to function well at low heights is particularly important when considering the cost of a high tower necessary for traditional turbines. All big companies in this industry, such as WePower, Urban Green Energy, Mariah Power, and Helix Wind, have reported sharply increasing sales over the previous years.

Dynamic braking regulates the speed by dumping excess energy, so that the turbine continues to produce electricity even in high winds. The dynamic braking resistor may be installed inside the building to provide heat (during high winds when more heat is lost by the building, while more heat is also produced by the braking resistor). The location makes low voltage (around 12 volt) distribution practical.

Local use

In the United States, residential wind turbines with outputs of 2–10 kW, typically cost between $12,000 and $55,000 installed ($6 per watt), although there are incentives and rebates available in 19 states that can reduce the purchase price for homeowners by up to 50 percent, to ($3 per watt). The US manufacturer "Southwest Windpower," estimates a turbine to pay for itself in energy savings in 5 to 10 years.

The American Wind Energy Association has released several studies on the small wind turbine market in the U.S. and abroad, showing that the U.S. continues to dominate the Small Wind industry.[1] According to another organization, the World Wind Energy Association, it is difficult to assess the total number or capacity of small-scaled wind turbines, but in China alone, there are roughly 300,000 small-scale wind turbines generating electricity.

The dominant models on the market, especially in the United States, are horizontal-axis wind turbines (HAWT).

Parts

• Blades
• Hub
• DC generator
• Diode
• Mount
• Wires
• Tail

Tower

• Base
• Pole
• Guy-wires

Loopwing

The Loopwing turbine is a low-noise, low-vibration and self-stabilizing device. It is specifically designed for quiet home use. It requires only a 1.6 mph (2.6 km/h) breeze to get started.

DIY and Open Source Wind Turbines

Some hobbyists have built wind turbines from kits, sourced components, or from scratch.

Do it yourself or DIY-wind turbine construction has been made popular by magazines such as OtherPower and Home Power, and websites such as Instructables, and by TV-series as Jericho and The Time Machine and build websites [2]

DIY-made wind turbines are usually smaller (rooftop) turbines of ~ 1 kW or less. These small wind turbines are usually tilt-up or fixed/guyed towers. However, larger (freestanding) and more powerful windtubines are sometimes built as well. The latter can generate power of up to 10 kW. In addition, people are also showing interest in DIY-construction of wind turbines with special designs as the Savonius, Panemone, wind turbine to boost power generation. When compared to similar sized commercial wind turbines, these DIY turbines tend to be cheaper.

Through the internet, the community is now able to obtain plans to construct DIY-wind turbines. and there is a growing trend toward building them for domestic requirements. The DIY-wind turbines are now being used both in developed countries and in developing countries, to help power homes, residences and small businesses. At present, organizations as Practical Action have designed DIY wind turbines that can be easily built by communities in developing nations and are supplying concrete documents on how to do so.

Open source

Main article: Open hardware

To assist people in the developing countries, and hobbyists alike, several projects have been open-sourced (e.g. the Jua Kali wind turbine, Hugh Piggot's wind turbine, ForceField Wind Turbine, Chispito Wind Generator.)

See also

• Wind turbine
• Wind turbine design

References

• Dan Fink; Dan Bartmann (2008). Homebrew Wind Power. Buckville Publications LLC. ISBN 0-9819201-0-1. 

Footnotes

^http://Wind-Turbine-24v.com Website With Information on Building Small Wind Turbines

External links

• Website offering professionally made plans, 3D models and an animation for building your own wind turbine
• A Dutch government test of 10 wind turbines with English summary here and here
• All Small Wind Turbines | Portal to the world of Small Wind Turbines 400+ turbines listed
• Challenges of Introducing Reliable Small Wind Turbines
• Small wind turbines (Environmental and Energy Study Institute).
• Fact sheet by American Wind Energy Association (AWEA)
• Chispito Wind Generator (DIY) that can be made from parts in most cities in most countries, throughout the world.
• Hot Home Wind Turbines You Can Actually Buy, Plus One You Wish You Could (TreeHugger).
• - intelligent wind turbine control
• Working the Field of Bio-lnspired Design BioInspired! May 31, 2009, Volume 7, Issue 2, Page 10, The Biomimicry Institute

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