What is Wind Electricity?

Beginner
An Endurance S-343 on a 90-foot hydraulic tilt-up tower.
Vince Culp of Energy Unlimited gets ready to raise an Endurance S-343 on a ninety-foot hydraulic tilt-up tower.
Wind Turbine Tower Siting
Main: To recoup your investment, wind turbines should be sited far from, and well above, any obstructions to the wind. Inset: A wind turbine on a short tower is a waste of money if your goal is to produce energy.
Rotor Diameter & Swept Area Illustration
Comparison of the rotor diameter and swept area of several popular wind turbines.
Wind Turbulence Illustration
Turbulence slows and degrades the wind resource, both upwind and downwind of obstructions. Note the height (H) and distance of turbulence behind an obstruction­—an unsuitable area for a wind turbine.
Residential-Scale Wind Turbines
An Endurance S-343 on a 90-foot hydraulic tilt-up tower.
Wind Turbine Tower Siting
Rotor Diameter & Swept Area Illustration
Wind Turbulence Illustration
Residential-Scale Wind Turbines

What is Wind Electricity?

Wind energy is a dynamic if invisible resource—the energy available in a moving mass of air. From grain grinding by simple wind-driven machines in ancient cultures to modern electricity-generating devices, the wind has been tapped to work for us.

Wind is a cubic energy resource. As the wind speed increases, the power available increases cubically. This means that it’s very important to get into higher wind speeds, and the way we do that is with taller towers. Regardless of the turbine or tower type, going higher is the tried-and-true, reliable way to increase performance in a wind generator. And the most common mistake in wind electricity is installing a turbine on a short tower.

The swept area of a wind turbine is the second most important factor (after the wind resource itself) that determines energy production. The circle “swept” by the blades is the collector area. It’s not possible to get a large amount of energy out of a small collector area. Betz’ theorem says we can only get about 60% of the energy out of the wind before we start slowing it down too much and actually decreasing performance. In the real world, well-designed machines can achieve about half of that.

Turbines can be divided by orientation, directionality, generating mode, and by other characteristics. Horizontal-axis wind turbines (HAWTs) are the most common and effective orientation. Vertical-axis wind turbines (VAWTs) may appeal to the uninitiated, but continue to disappoint as far as performance and longevity—both of the machines and the companies. Upwind (the wind hits the turbine before it hits the tower) and downwind (the wind hits the tower before it hits the turbine) designs can both be very effective.

Generating devices generally fall into one of three categories. Most home-scale turbines use permanent magnet generators (PMGs), which typically have fixed coils of copper wire and rotating groups of magnets that pass by them. Some older machines use wound-field alternators, which use a small amount of the wind energy to create electro-magnetism in the rotating part of the alternator. Induction motor/generators use conventional induction motors, but have the wind push them beyond their normal operating speed, which takes them from using electricity to making electricity.

Three basic tower types are used for residential wind-electric systems. Freestanding towers are the most expensive, but can be installed in very close quarters, and are perhaps the safest to install and maintain. Tilt-up towers allow all maintenance and repair to be done on the ground, but require a large open area for installation and use. Fixed-guyed towers include lattice and pole styles that do not tilt, and must be climbed for installation and service. These are typically the least costly, and need a moderate area for installation.

A wind-electric system is much more than just the wind generator and tower. Also required are transmission wiring, electronic controls, batteries if storage or backup is desired, an inverter for household AC or grid-interconnect, as well as metering, overcurrent protection, and other standard electrical components. All appropriate components should be chosen for compatibility and functionality—it takes a whole system to make wind electricity.

Comments (6)

Richard Cox's picture

I have a 2.5 kwh wind turbine connected to the grid when the voltage is above 220v. However there are many times the voltage is below 220v. How can I use this low voltage in my home anyone?

Ian Woofenden's picture

Richard,

Every wind turbine has a cut-in speed and voltage, below which it is not generating enough energy to bother capturing. Unless it is poorly designed, your machine is no different, and will begin generating when there is sufficient wind energy. It may seem alluring to try to capture every scrap, but a machine designed to capture very low levels of wind energy will likely not do well at the energy-intensive levels you want it to be designed for.

If you want to get more nerdy, look into "distribution curves", which show how frequently typical sites receive typical wind speeds. Then also consider the cubic nature of wind power, and do a little simple math like "4 X 4 X 4" and compare the result to "10 X 10 X 10" or "15 X 15 X 15". More detail can be found in my article here:
http://www.homepower.com/articles/w...

Ian Woofenden, Home Power senior editor

Alfred Finnell 2's picture

More than likely, you are generating DC from the turbine. This is then converted to AC by way of a grid tie. You cannot up the voltage of DC with a transformer. More than likely, you can replace your grid tie. Check voltage off the generator to see what you have.. It may be AC, and may be DC. If AC, transform.

Eric Vanhuffel's picture

I am relatively new to this game but having a good background i electicity and maintenance engineering i am perhaps not so green and have some common sense when it comes to reality in energy .
I have bought a 350 watt hawt and a 50 watt vawt just to play with .
I am living on the edge of a small town in the fjords close to mountains. Close to the mountains means about 60 yards back of my house starts the foot of a mountain 700 yards high.
I have bought a 160 ampere dump charger for the hell of it and if i want to upgrade my turbine i don'have to buy a new one.
Turbines are both 12 volt and i know what this means in cable , but if i screw in a sufficient cable now it will hold with a larger 3fase generator.
Later on there is going to be a pv system which will grow over the years and will also be connected to the dump charger and the warm water tank.
I have a diy solar collector (air) and this works . This made me think about natural energy and how we can use them.

Alfred Finnell 2's picture

Read the books by Paul Gipe. Then you will take the VAWT and use it for parts or a boat anchor.

Maggie100's picture

When it comes to heating our homes, we should be looking at more environmentally sound way of doing this. This is a great article that helps you appreciate, exactly what goes into heating your home.

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