Wind Power on your home? Really?

Posted In Wind - By WhyGREENPower On Thursday, July 7th, 2011 With 8 Comments

The American Wind Energy Association (AWEA) reports that the U.S. market for residential
wind power turbines – those with capacities of 100 kilowatts (kW) and less – grew 78% in
2009 and continues to grow at a rapid pace.

The largest sector of this market is residential wind turbines in the 400watts -10 kilowatt (Kw) range and are the focus of this WhyGREENPower.org post.

The wind Turbine that I just installed on my home is a custom roof mounted 600 watt unit and starts producing power with as little as 4.5 miles an hour wind speed.  The type of setup that I choose is a “Battery Wind System”(see below) and complimented with a integrated Solar Panel solution.  I will be publishing a future post that will talk about the harmony that is achieved when you install both solar and wind on you personal residence.

Wind Turbine Residential Install

Wind Turbine and Weather Station Residential Install

The mechanics of a wind turbine are pretty basic. In most small wind turbines the rotor
(propeller blades and hub) are connected directly to a generator.  The generator produces wild 3 phase alternating current (AC). The wild AC is rectified to direct current (DC) and either stored in a battery bank for future use, or sent through an inverter and modified into appliance friendly AC power for immediate use.

Grid tied wind systems
When the power from the inverter is routed directly into your home’s main circuit panel
you have a grid tied system. A grid tied wind system provides electricity to your home
only when there’s sufficient wind. On calm windless days your home will rely on the
“grid.” Most residential turbines will not produce usable amounts of electricity until the
wind speed exceeds 7 mph. Some of the more modern ones are less than 5 mph.

Battery wind systems
Another option is to route the power directly into a battery bank for current and future
needs. The incorporation of this type of system into your lifestyle is referred to as
“living off the grid.” But to ensure that 100% of your power demand is met you must
carefully size the system taking into account wind resources, turbine size, and tower
height.

Hybrid wind power systems
The third option is a combination grid tied system with a battery backup. A battery
backup is good to have when the grid is down or on windless days, but it will add
about a third again as much to the total cost of the system. For this reason, the
majority of wind systems sold are grid tied only.

Some manufacturers make only battery-charging machines, and may offer a variety of
turbine voltages. Others produce machines intended to connect to grid-synchronous
inverters without batteries. One machine by Skystream integrates the inverter with
the turbine.

Wind turbine power ratings
All home wind power generators are assigned a Kw (kilowatt) rating by their
manufacturers. Unfortunately, the peak power “rated at” Kw number assigned to
various wind turbine models is meaningless since there is no accepted, industry wide
standard for measuring a turbine’s output. The rating inconsistencies are mainly due
to differing “example” wind speeds used by individual manufacturers to calculate peak
power.

A more accurate approach to estimating the energy output of a turbine at various
wind speeds is to use the chart provided on the manufacturer’s website.
The chart on the left illustrates estimated monthly output in kWh (kilowatt hours)
based on average annual wind speed for the Whisper 500 by Southwest Windpower.

At average wind speeds of 10 mph you could expect 300 kwh of energy production.

At average wind speeds of 12 mph the energy output is around 500 kWh.

Notice that a 20% increase in wind speed from 10 to 12 mph yields a 66% increase in
energy production.

Wind speeds are typically highest during winter months and taper off throughout the
summer. To illustrate this, you can view a monthly kWh production chart kept by the
owner of a Skystream 3.7.

What are the requirements for a viable wind powered system?
1. Zoning laws that enable the installation of wind powered systems. The first place to
start is your town’s building department. Here’s a link to a short but instructive zoning
overview for small wind turbines. (PDF)

2. Sufficient land and open space. The land requirement will depend on zoning laws
but the suggested minimum is one acre. As far as open space goes, the tower and
generator should be sited in an area free of obstructions for 500 feet around the
tower.

3. Wind – the minimum requirement is 10 mph average annual wind speed. As the
monthly energy chart above shows, a seemingly insignificant increase in wind speed
pays big dividends. The most cost effective method to increase wind speed is to
increase tower height.

Find your local wind speed in 2 easy steps
1. Click on your state (click again to enlarge) on this wind resource map. Look at the
color coded Wind Power Classifications and determine if you live in a Class 2 or better
area. If your area is designated Class 1 you should consider solar power instead.

The one drawback to the maps you just viewed is the wind speed measurements
were taken at 50 meters, or 164 feet, and don’t accurately reflect the wind speeds at
the top of shorter towers used for home wind generation.

2. A more accurate, though still imperfect solution to this problem can be found at this
table of average wind speeds. This resource lists the wind speeds at elevations closer
to standard tower heights. Choose a city or town closest to your own and look at the
far right column labeled ANN for the annual average wind speed. Your best chance for
meaningful power generation lies in areas where the wind speed exceeds 10 mph.

Wind power production calculator
Once you estimate wind speed it’s easy to predict the power output from any size
turbine by using alternative-heating-info.com’s Monthly kWh Calculator. The only other piece of
information you’ll need is the length (also referred to as diameter) of the generator’s
propeller.

With all this said, it is important to note that some Wind Turbines now are producing power sub 5 miles per hour, like the unit I installed. Also note that when you install in a place like your roof, all the air is directed to your roof funnels up towards your wind turbine creating a similar effect when you are in an Urban area between large building… increased Wind Power… that can make GREEN Power. 🙂

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Displaying 8 Comments
Have Your Say

  1. Guy says:

    Very well done! You covered all the issues for installing a residential wind turbine. Only thing I would add is that if you plan on installing an expensive wind turbine and have doubts about the wind speed you have at your site, then you should install a wind gauge (anemometer) at the intended location and get a year’s worth of data first. I did this an learned that my average wind is about 4.5mph – not viable. An inexpensive weather station can be found for about $100, read my blog to see what I did and what I learned:
    http://www.arttec.net/WindPower

  2. Damian says:

    Very useful post. Please keep up the good work. I’m trying to calculate wind speed in Boston where I live so that I can also install wind turbine.

  3. Richard says:

    Good Blog. Please keep writing on this interesting topic. But I have some serious doubts about installing Green Power. Because of zoning laws and land requirement i think that this is not an easy and viable option for everyone. We need much more advancements in technology to make it affordable to masses.

  4. David says:

    Thanks for this nice and informative article.I think that there are lots of obstacles in mass acceptance of Green Power as a viable source of energy.As you mentioned in this post that a person is dependent on Zoning laws,Sufficient amount of Land and Wind speed to generate Green Power.SO we must try to lower the barriers for this Industry from a consumers point of view .Governments all over the world must do more to promote Green Power as a safe and Eco friendly source .If we see this in the light of Sunami and Nuclear Accident in Japan then it has become more important now than before to promote Green Power .

    • Linda Carter says:

      Great info! I currently have solar on my home and I’ve thought about adding a wind turbine. Would be interested to know what the maintenance is like.
      Thanks,
      Linda

  5. Neil Johnson says:

    Very good and informative blog.I’m very impressed by your writing style .You have explained such a technical thing in the best possible and simple way

  6. Mark Edwards says:

    After reading this post and assessing my own requirements I think that Wind System complimented with Solar Panels & battery storage are the best combination. I know some advocate the Grid tie systems but that doesn’t do you much good when there is no guarantee of sun for days. Keep it up, I like this website!

    • Alex says:

      It depends on a persons requirements.Maybe Battery wind system is good for you but it doesn’t means that it is good for everyone

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