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Small Wind Turbines - Residential
Let's take a look at the low end of wind turbines, units that you can use for your house, cottage, cabin or "special uses". These units vary in size, from 400 watts up to 10 kilowatts in size.
What size do you need?
For a house, cottage or cabin, that already has electrical power, take a look at your electrical bill. The bill will likely state how many kilowatts of electricity you used PER DAY for the last month. It may even included an average daily usage for each month in the past year.
This number is the average daily usage. A day has 24 hours as we all know. However, it is very unlikely that your usage is even throughout those 24 hours. You may use more power first thing in the morning, getting ready for work and again at night, preparing dinner. If you can use net metering, then you don't need to be concerned with the time of day usage as this evens out by storing your spare power on the grid.
- your local utility allows you to put excess power onto the grid and run your electrical meter backwards. Your "total" usage is read every so often and a bill for the electricity "used" is set to you.
Example: Day one, very windy for 18 hours, you generate 10 kilowatts of excess power that is put onto the grid. Day 2, wind blows for 8 hours and you generate 2 extra kilowatts of power that is put onto the grid. Day 3, 4 & 5 are quiet wind days and you use 15 kilowatts of power from the grid each day. For the 5 days, your total power usage is (-10) + (-2) + 15 + 15 + 15 = 33 kilowatts.
If you have determined roughly how much power you want to produce, from your existing usage (electrical bills), you next need to know how much wind you have. Wind Maps - such as this map for Canada and this map for United States indicate how much wind is produced on average for each site in the country. The Canadian map for example, provides the average wind speed at three separate elevations - 30m, 50m and 80m.
With the average wind speed determined for your site, take a look at the spec. sheets for some of the wind turbines and determine how much power each wind turbine is likely to produce for you. Here is an example using the AirX by Southwest Windpower - a very popular turbine:
Using the wind map for Canada and homing in on London Ontario, we can see that the Mean Wind Speed is 5.53 meters per second at a height of 30 meters above ground.
Using the top graph, Instantaneous Wind Speed, and our wind speed of 5.5 m/s we can determine that our average hourly power output would be approximately 40 watts.
Jump down to the second graph, Monthly Energy Output (kWh) and using our average wind speed of 5.5m/s, we can see that the average monthly power output for our site would be approximately 32.5 kilowatt hours.
The yearly power output, for an AirX 400 watt wind turbine, on a 30 meter tower (approx. 100 ft.) in London Ontario would be approximately 390 kwh.
As a comparison, 3 additional Southwest Windpower models would produce the following power at this site and height:
Whisper 100 - 2,100 kwh per year
Whisper 200 - 2,710 kwh per year
Whisper 500 - 7,850 kwh per year
Compare the yearly power outputs to the power you wanted to produce. This should help to narrow down the selection to a few good manufactures.
Tower height can have a significant impact on the amount of wind and the quality of the wind. All towers needs to be at least 10 meters (30 feet) higher than all objects within the immediate area (100 meters or 300 feet).
Lower towers can subject your turbine to wind turbulance. Not only does this rough wind reduce the power produced, it can also shorten the lifespan of the turbine or even cause failures during very high wind gusts. Often, the best money spent, is on a good quality, high, tower.
There are basically two types of towers for your wind turbine: Free Standing or Guyed Towers.
Used for virtually all large trubines (wind farms) and for areas where space is an issue.
For small turbines the tower is often made from lattice though pipe or tubing is also used.
These towers require a significant base, to support the tower and stresses caused by the wind.
Free standing towers tend to be more expensive than guyed towers.
They require a crane for assembly and placement of the turbine.
With a lattice tower, the lattice acts like a ladder in order to reach the turbine for routine maintenance.
The most common tower for smaller turbines.
Usually lower in cost that free standing, but requires much more space due to the area covered by the guys.
Both lattice and poles/pipes are used.
A Gin Pole is often used to raise and lower the tower.
Click here to see a video of raising a guyed tower. (3 mb in size!)
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