Wind Power Buying Guide
A quick guide to strategic product selection
Background
Wind has been used as a source of energy for thousands of years, but only now is the modern world embracing wind as a feasible alternative to fossil fuels. Today, it is the fastest growing energy source in the world. The U.S. Department of Energy, the American Wind Energy Association and the National Renewable Energy Laboratory all agree and believe that 20% of the nation's electricity can come from renewable wind energy within the next twenty years.
Wind power generation at home: the top 4 things to consider
- Amount of energy needed: how much energy do you want your system to ideally generate and for which purpose(s)? How much energy does your household use, on average, per month? What percentage of this demand would you like your turbine to generate?
- Average wind speed: what wind speeds can you expect to get, on average, where the wind power system will be installed? For most viable home sites, that number will be in the range of 8 - 14 miles per hour.
- Application: do you want the system to be roof- or pole-mounted? How tall can your turbine be? Note that roof-mounted systems typically are able to generate a small amount of energy as their rotor size is limited to 3 - 6 feet in diameter.
- Energy storage: Do you want the system to be connected to the grid or would you like to store any extra power in a battery banking system?
Residential wind power systems
Residential wind turbines were first commercialized in the United States in the 1920s and were fairly popular until the Rural Electrification Administration extended power lines to many rural communities in the 1930s. The oil crises of the 1970s spurred a flurry of renewed interest, but when tax credits and other government incentives dried-up in the 1980s, interest died as well.
Here we are in the 21st century and wind is once again emerging as a “new” alternative energy source. Advancements in technology, including improved efficiencies, extended transition capabilities and the new micro wind turbine for your average urban dweller has lifted the capabilities of modern wind power to serve residential energy demands. Not to mention the inviting tax incentives available for the installation of these renewable energy systems (see Eco-rate's Rebate Directory for details).
Determining the right size
Homes use approximately 9,400 kilowatt-hours (kWh) of electricity per year (about 780 kWh per month). Depending upon the average wind speed in the area, a wind turbine rated in the range of 5 to 15 kilowatts would be required to make a significant contribution to meet this demand.
A small system, say a wind turbine with rotors (turbine blades and hub) that are about 8 feet in diameter (50 square feet of swept area) peak at about 1,000 watts and generate about 75 kWh per month with a 10 mile per hour wind speed. A large turbines with rotors up to 70 feet in diameter (4,000 square feet of swept area) peak at about 100,000 watts (100 kWh) and generate about 8,000 kWh per month with an average wind speed of 10 miles per hour. Something in between these two sizes would be ideal for a residential setting.
► Know your household's typical monthly energy usage in kilowatt hours before you make your wind turbine selection. Your local utility should be able to help you with this.
Proper tower sizing
Wind is at its most desirable speeds well above buildings and other obstructions near the ground. Wind speeds close to the ground are often weak and turbulent, and therefore won't help your turbine provide much energy to you. Tall towers are essential to putting wind turbines where they can do their job best.
According to Home Power, the lowest point of the turbine rotor should be at least 30 feet above anything within 500 feet (the taller, the better). On most sites, that translates to towers between 80 and 140 feet tall. Sometimes, even taller towers are required.
Determining wind speed
As noted above, it is very important that you know what kind of wind speeds you can expect to get at your property before you install a wind power system. This will help you determine which product to purchase as some are more efficient at generating power at lower wind speeds than others.
Call you local weather service to ask about the wind speed in your area or visit the U.S. Department of Energy's Wind & Hydropower Technologies Program website.
Rated power
Rated power is a measurement used to refer to the amount of energy (kWh) a wind turbine will be able to generate when operating at specific conditions of operation (i.e. a particular wind speed). For example, if a wind turbine has a rated power or nameplate power of 1000 kW, the wind turbine will produce 1000 kilowatt hours of energy per hour of operation, when running at its maximum performance.
It is important to know that manufacturers and vendors of wind turbines often use high wind speeds to determine rated power, typically 25 miles per hour. However, wind speeds of 10-12 miles per hour are much more common.
► Eco-rate will soon feature wind turbine products that are rated according to their energy (kWh) output at 11 mph.
Buying tip: Instead of looking at rated power to evaluate how much energy the wind turbine will likely generate for you, try and find documentation on the product's estimated monthly and/or annual kilowatt hour (kWh) output.
Micro wind turbines
Systems smaller than 1.5 kilowatts are considered micro wind systems. Micro wind turbines are unlike their commercial counterparts: they are small, quiet and architecturally inspiring. They are not intended to take you off the grid however; rather, they are designed to help offset energy costs and reduce your demand on conventional power generation. These systems can power water pumps, appliances and lighting, but are not a whole house solution. Micro systems can also work well as part of a hybrid solution, combining wind power generation with solar power generation.
Economics
The American Wind Energy Association claims that a wind turbine has the potential to lower electricity bills by 50 - 90% and that "It is not uncommon for wind turbine owners with total-electric homes to have monthly utility bills of only $8 - $15 for nine months of the year."
Return on investment potential for wind turbines greatly depends on: 1) the availability of decent wind speeds at the installation site, and 2) the government rebates and incentives available in your area. As a general rule of thumb, a turbine owner should have at least a 10 mph average wind speed and be paying at least 10 cents/kWh for electricity for a wind turbine to be cost-effective. Check with your local weather service to determine wind speed and with you local utility to determine cost per kilowatt hour of electricity. You can also view the U.S. Department of Energy's 50-Meter Wind Resource Map by clicking here.
Another critical element is the net metering offerings of your local utility company. If your wind system is connected to the power grid, your excess power can be sold to the utility company at retail rates. This scenario mixed with the recently enhanced federal government incentive programs can contribute to a quick return on your investment. Keep in mind that your local building codes may have restraints on wind turbine installation, particularly in urban settings.
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