Wind power is an attractive source of renewable energy with practically zero environmental impact. When properly installed, residential wind turbines provide a significant portion of a household’s energy needs. They can be used as an alternative source of energy in combination with photovoltaic systems, or integrated with a utility grid.
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FAQs
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It is an interesting fact that wind energy is actually related to solar energy. The process begins with the sun unevenly heating different areas of the Earth’s surface. Warm air above heated areas rises and cool air rushes in to take its place. This creates wind. 
As long as the sun heats the earth, there will be wind and the potential to use it. Mankind has been harnessing wind energy for thousands of years by using sails to move boats, and by building windmills to crush grain and move water.
Mechanics of a wind turbine
Most modern wind turbines use a design similar to a traditional windmill, called Horizontal Axis Wind Turbines (HAWTs). Vertical axis wind turbines (VAWT) also exist but are far less popular. (see photograph)
Wind turbines convert the wind’s kinetic (motion) energy into electric energy. When wind blows against the turbine’s blade, it not only pushes it, but creates a pocket of low pressure on the opposite side of the blade, which sucks the blade back onto itself. These two forces, called drag and lift, make the blades rotate. The blades are mounted to a rotor and connected to a generator by a series of shafts, which increase the final rotation speed to over 1,000 RPMs. When the generator turns, it produces electricity. Wind turbines are usually equipped with various control devices and braking systems. Brakes prevent damage by stopping the turbine when wind speeds get too high.
Modern horizontal axis turbines usually have fewer blades than their traditional counterparts. However, these two or three blades are much longer in diameter (up to 55 m). Residential models are only about 8 m and are, therefore, more energy-efficient. Blades are mounted on tall towers to avoid near-ground turbulence and to catch stronger and steadier winds that blow above the ground. Energy production is exponential to wind speed. Therefore, when wind speed doubles, energy production increases eight times, as long as wind speed is within the turbine’s range.
What are the environmental benefits of using wind power?
Wind is a clean fuel and offsets pollution from other sources, such as electric power generated by your utility company. A typical 10 killowatt (kW) wind turbine will offset approximately 1.2 tons of air pollutants, and 250 tons of greenhouses gases over its operating period.
Can I sell excess energy back to the utility company?
If your system is connected to a utility grid (grid-tied system), and produces more energy than your home uses, utility companies buy back the excess power. This buy back is called Net Metering or a Feed-In-Tariff. During times of excess energy, the inverter converts electricity to the utility’s standards, allowing the company to purchase the energy as it flows backward through your meter. Currently, 39 states allow connection of PV to the grid, and 36 states require net metering for utility companies. Ask your utility company about local policy. A customer may use power from the utility during the night or on a cloudy day. At the end of the month or year, the electricity bill shows whether the wind system produced more or less energy than the customer used. If more, the customer pays the difference. If less, the utility credits the customer at a wholesale price.
How does wind power compare with other renewable energy sources?
Small wind turbines may be the least expensive power option for a home not connected to the utility (an off-grid site). Wind power is economically competitive in rural settings with other energy sources like photovoltaics (solar power) and biomass.
Are wind turbines safe for people, structures, and animals?
Wind turbines have an excellent safety record. A chance of a tree falling on a house is greater than any danger from a wind turbine. Some people are concerned with ice accumulating on the blades. If this happens, the ice will usually fall straight down instead of being thrown. Birds rarely collide with small residential wind turbines.
How much does a wind system cost? What is the expected return?
In the U.S., small wind energy systems cost around $3,000-5,000 for every kilowatt of their capacity, or about $40,000 for a typical 10 kW system. Return on investment depends on average wind speed and local electricity costs. For example, if you pay 12 cents per kilowatt-hour (kWh), and have an average wind speed of 10 mph, payback time is between 6-16 years. Although larger turbines have higher initial and installation costs, they are more productive and may shorten the payback period.
Other factors include interest on loans and incentives in your state or country. Some financial incentives include the following:
- Rebates
- Buy-down programs
- Property and sales tax exemptions
- Net metering policies
- Increased property values.
- Subsidized loans
What is the optimal size of a wind turbine for my house?
An average household uses about 9,400 kWh of energy per year. A 10-kW wind turbine, installed at a site with average wind speeds (12 mph), generates about 10,000 kWh in a year. Smaller turbines are sufficient for locations of higher wind speeds, and homes with smaller energy needs.
How much maintenance does a wind turbine require?
After installation, wind turbines should require little maintenance. Some turbines operate up to five years without any attention. You can often arrange an annual maintenance service with your supplier. Simple maintenance includes:
- Tightening bolts
- Checking electrical connections
- Checking for corrosion
- Checking for wear on blades
- Replacing blades and bearings (after ten years)
Where do I have to live to be able to use wind power?
Average wind speed in your area is the primary factor to determine benefits from a wind turbine. Wind speeds of 10 mph (or about 5 m/s) are recommended. Keep in mind your site terrain and structures that may block wind. Check your local wind speeds with the map below. 
For a detailed map of wind speeds in your area, look on a government energy website.
An experienced evaluator can provide an estimate of your site’s wind potential, even without a costly collection of wind measurements. Since residential wind turbines are large structures, they are unsuitable for urban or small suburban house lots. Experts recommend at least 1 acre of property. However, some turbines mounted on top of small towers have been successfully installed on urban rooftops.
There are about 67 companies (20 in the U.S.) that manufacture small wind turbines. Small wind energy systems cost about $3,000-$5,000 for every kilowatt of capacity (U.S. prices). Most common sizes of wind turbines used by homeowners range between 5 to 15 kW. This makes an average 10 kW turbine cost about $40,000. Smaller turbines, such as 1 kW and less are available. State or government credits may be available. Check with your state energy office.
In 2007, retail costs of electricity from small U.S. wind turbines declined from 15-18 cents per kWh to 10-11 cents per kWh. Prices are predicted to drop down to 7 cents in the next few years. Compare these prices with photovoltaic (solar panel) electricity costs at about 18 cents per kWh.
Factors that affect cost and productivity
Average wind speed at the site. Experts recommend an average wind speed of at least 10 mph (or 5 m/s) for any wind turbine to function effectively. If the wind speed is too low, the turbine won’t function at its full potential.
Technology of the turbine. The larger the wind swept area of the turbine, the higher the price, but the more cost-efficient it will be in the long run. Calculate the trade off between higher initial investment, and lower energy costs from a more powerful turbine. Larger turbines also require taller towers. Price is also affected by adding high-tech options, such as computerized control devices.
Construction costs. Wind turbines are large structures that require special equipment. Both installation and shipping are a significant part of total costs. Chose a supplier nearest your home. Final costs increase if turbines are installed on a difficult terrain, such as a hillside.
Performance and return periods
A well-sited turbine may cut your utility bills by as much as 80%. A 10 kW turbine installed at a site with average wind speeds of 12 mph generates about 10,000 kWh of electricity annually. If your turbine is connected to the utility grid, you can sell extra electricity back to the utility company. See FAQ above
Return period for investment depends on your energy needs and the local cost of electricity. A typical California home consumes 9,400 kWh of energy per year and pays the utility 12 cents for each kilowatt-hour. Payback time for a 10 kWh wind turbine in this home would be about 20 years. After the investment is paid back, the turbine will generate electricity almost for free, and will provide up to $20,000 of savings in the next 10 years. Most manufacturers guarantee wind turbines for 30 to 50 years.
Wind is a clean, renewable source of energy – it won’t be used up faster than it can replenish itself, like other fuel sources. Using wind energy helps to decrease our dependency on fossil fuels, and diminishes greenhouse gas production. A typical 10 kW wind turbine will offset approximately 1.2 tons of air pollutants and 250 tons of greenhouse gases over its operating period.
Sometimes, birds and bats collide with large industrial wind turbines, but not often with small residential size towers. The attractiveness of wind towers is subjective. Some consider wind towers sticking out high into the sky a visual pollution. But for others, it is a practical replacement to conventional power plants. Small wind turbines are usually quiet in operation and they don’t interfere with TV or radio reception.
Consider wind turbine equipment as you would any major purchase. Weigh costs and various degrees of durable designs. Obtain product literature from several manufacturers, and ensure the company is a recognized business. Determine that parts and services are available when you need them. Find out the warranty length and what it includes. Search for a supplier on this web site.
Finding a contractor
There are no certification agencies for wind turbine contractors, but some countries are planning them for the next year or two. When choosing a contractor, take note of their local experience, their certifications or licenses, and their warranty policies. Ask for the business’ references of customers who installed a similar wind system. Ask system owners about performance, reliability, maintenance, and repair requirements. Find out if the system is meeting their expectations. Also, make use of your contractor’s knowledge of local incentives and regulations, especially if they can help you with applications.
Most regions of the world have established wind energy associations that list providers and contractors. If you’re unsure about your region, check the Global Wind Energy Council (GWEC)
Numerous homeowners have successfully installed wind systems and eliminated most of their electricity bills. They usually purchase electricity only to run air-conditioning during summer months. Utility companies pay wind power producers with net metering for excess electricity. Their power supply is never interrupted during a blackout.
- A poultry farm in Masstown, Canada, produces 75 percent of their electricity using 3 wind turbines, which also supply power to the owners’ two residential homes.
- Robin Wilson’s Idea Home in San Francisco provides an exciting example of the possibilities of wind power. A small roof-top wind turbine sitting on a 45-foot pole powers the home. The owner’s goal is to live off-grid, even while located in the center.
