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 (19)

ideas2014's picture

dear all i am new subscriper here and would to share with u if any one can help me ....what is the max distance i go for connection bewteen my battery powerbank and the inverter ,,i know it should be small and shortest as possible .i,e can i go for 10-20 m wirring length ,,what is the constraints
my power capacity is 10 kw , and power bank voltage 48 VDC

Alfred Finnell 2's picture

Are you sure you are going to get 10KW? That would require a turbine of about 25 ft diameter.
48vdc at 10kw is 20 amps. DC requires at least double the size of AC to transmit. AC requires 12 ga wire. I would use 12ga, black and white paired, for + then the black on a second wire, and the white and two grounds to give triple the requirement of a 12g 20 amp circuit. Do not be surprised if all you get is perhaps 10 watts, not 10,000 There are a lot of liars in the field.

Michael Welch's picture

Alfred, please rethink your advice. He is talking about cabling between the battery and inverter, which can carry HUGE amounts of current. The amount of power that his source can produce is irrelevant to the topic.

Battery cables need to be short and large because of that current. For example, my battery cables in my small home are 0000, and six feet long.

Alfred Finnell 2's picture

Hi, Yes, DC requires lots more wire. This is why Westinghouse (Tesla) won over on AC v DC (Edison) . The numbers given were run through Ohms law, and that is where I did the estimates. I tripled the requirement for AC to come up with the wires . I really do not know the actual device to make the power. Most stuff that I have seen by "developers" are lies.
Look at tensionturbine.com and see something new The Tensionturbine configuration 16 feet diameter, makes 3000 watts maximum according to the math. Real power numbers will be published.

ideas2014's picture

thanx alfred for sharing yr comment with me ..i dun have actually wind turbin ,,but some thing similar called Smart HUMP ,,it is device installed in the road to generate energy from moving vehicles on roads ,,,most of my application the house or the facility Main panel is aroun d10-20 meter from my Generator and powerbank which is underground and proper vetilation ..but for monitoring and maintenance purposes i want make my inverter close to my client main panel ,..but in this case as u see i need wirring for the DC coming from the power bank to reach the inverter

so i can understand from your comment ,,No problem with that ?
thanx for sharing any further info or advises around this point

Alfred Finnell 2's picture

I did an edit of the wire I would use on a 20 amp DC circuit. You will find it above your comment.
thanks, alfred

Ben Root's picture

If I understand you correctly, generating electricity from moving cars is actually generating electricity from gasoline (stealing energy from the car). At best, it is no better than (and probably less efficient than) burning petrol in a generator. And at worse, it is stealing energy from the car's owner who is paying for the petrol in the tank.
Maybe this could only be advantageous for gaining a small amount of energy at a remote location, like powering electronics at a ticket booth far from grid access.

ideas2014's picture

dear Ben ..i am sorry to tell you ,,your assumtion is totally wrong ,,we dont steal any energy from cars ,,but we only install our hump after the speed humps on roads and at car parkings where u have to use yr breaking system only ,,,during this distance u must exctract and convert your mechanical energy ( which u have to lose any how to stop yr car ) into heat ,,,during this distance and time which varies depending on your speed and how u stop your car ,,,what u do is lost energy ,,u can have now use for it ,,same concept about EV when harnessing energy from regenrative breaking system at EV if u have an idea about the concept ...

i think Ben u just attacked me without any understanding or dicussion ,,anyway thanx and wish u great day
ihab

Ben Root's picture

Hello Ihab,

Please, no attack was intended. I was questioning your idea based on only a small amount of detail. Because I hear of similar ideas all the time from people who do not understand conservation of energy and efficiency losses, I try to help them understand. Now I do understand that your design is intending to use deceleration, energy that would otherwise be wasted as heat. Thank you for clarifying. I wish you the best success with your project.

Alfred Finnell 2's picture

Instead of twisting all three, twist the black and white of two romex 12 ga together and use as + Use the two grounds and then a third external as the - . This will give you better insulation on the + side.

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?

Alfred Finnell 2's picture

You do not. The grid is the buffer.

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.

Alfred Finnell 2's picture

In keeping a house warm insulation is the key. Electric power will most likely be just not enough.
The math says that 3000 watts requires at least a 16 foot turbine. Look at tensionturbine.com to see what the new development is.

Ian Woofenden's picture

Insulation AND air sealing are key. Lots of insulation with poor air sealing will not a warm or efficient home make. A blower door test of an existing home or testing a building envelope during the construction process will help you see its true value.

While "heating with electricity" has a bad reputation historically, today -- using mini-split air-source heat pumps -- it is one of the best choices. Not only is it energy efficient and cost effective, but it's also a renewable energy option, since it uses naturally occurring ambient heat in the outside air. And it gives you the option (unlike fossil fuel heating systems) of using renewable electricity -- either generated on site or purchased from your utility.

Ian Woofenden, Home Power senior editor

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