If you have enough wind resources in your area and the situation is right, home wind turbines are one of the most cost-effective renewable energy systems at home with zero emissions and pollution.
Small wind electric systems can:
- Lower your electricity bills by 50%–90%
- Help you avoid the high costs of having utility power lines extended to a remote location
- Help uninterruptible power supplies ride through extended utility outages.
Small electric wind systems can also be used for a variety of other applications, including water pumping on farms and ranches.
In this article, we will discuss how to plan, install and maintain a small wind turbine and the total cost.
How a Small Wind Electric System Works
The wind is created by the unequal heating of the Earth’s surface by the sun. Wind turbines convert the kinetic energy in wind into clean electricity. When the wind turns the wind turbine’s blades, a rotor captures the kinetic energy of the wind and converts it into rotary motion to drive the generator.
Home wind turbines are a smaller version of the large turbines you see on the side of the highway generating clean electrical energy from the wind’s kinetic energy.
Most turbines have automatic Overspeed control systems to keep the rotor from spinning out of control in very strong winds. Our wind power animation has more information about how wind systems work and the benefits they provide.
A small wind system can be connected to the power grid via your electricity supplier or it can stand alone (off-grid). This makes small wind electric systems a good choice for rural areas that are not already connected to the electric grid.
Small Wind Electric System Components
A wind-electric system consists of a wind turbine mounted on a tower for better access to stronger winds. In addition to the turbine and tower, small wind turbines also require system balance components.
Most small wind turbines manufactured today are horizontal-axis, updraft machines that have two or three blades. These blades are usually made of a composite material, such as fiberglass.
The turbine’s frame is the structure onto which the rotor, generator, and stern are attached. The amount of energy a turbine will produce is determined primarily by the diameter of its rotor. The diameter of the rotor defines its “swept area,” or the quantity of wind intercepted by the turbine. The stern keeps the turbine facing into the wind.
Since the wind speeds increase with altitude, a small wind turbine is mounted on a tower. The higher the tower, the more electricity the wind system can generally generate.
Relatively small investments in a higher tower height can lead to very high returns on electricity generation. For example, raising a 10-kilowatt generator from a 60-foot tower to a 100-foot tower increases the overall system cost by 10%, but can produce 25% more electricity.
Most turbine manufacturers provide wind energy system packages that include towers. There are two basic types of towers: self-supporting (free-standing) and guyed. There are also fold-down versions of guyed towers. Most home wind turbine uses a guyed tower, which is the least expensive and is easier to install than self-supporting towers.
However, because the guy radius must be one-half to three-quarters of the tower height, guyed towers require enough space to accommodate them.
While tilt-down towers are more expensive, they offer the consumer an easy way to perform maintenance on smaller light-weight turbines, usually 10 kilowatt or less. Tilt-down towers can also be lowered to the ground during hazardous weather such as hurricanes. Aluminum towers are prone to cracking and should be avoided.
Balance of System Components
The system compensation parts you need for a small wind electric system depend on your application in addition to the wind turbine and tower. For example, the parts required for a water pumping system are very different from what you will need for a residential application.
The balance-of-system parts required also depend on whether your system is grid-tied, stand-alone, or hybrid.
Most manufacturers can provide you with a system package that contains all of the parts you need for your specific application.
For a residential grid-connected application, the balance-of-system parts can include:
- A controller
- Storage batteries
- An inverter (power conditioning unit)
- Electrical disconnect switch
- Grounding system
- Foundation for the tower.
Planning a Small Wind Electric System
Small wind electrical systems must be planned to determine whether there is enough wind, the location is appropriate, whether wind systems are acceptable, and whether the system is economical.
In the case of small wind turbines, it must be planned whether there is enough wind in your region on a constant basis, whether the location for the system corresponds to the requirements of the system, whether zone codes or covenants allow wind systems in your region and whether the system will take into account all these elements be economical.
Estimating your Wind Resource
To determine the suitability of your site for a small wind electrical system, you need to estimate your site’s wind resource. The wind resource can vary considerably over an area of just a few kilometers due to local terrain influences on the wind flow. You can use the following methods to estimate your wind resource.
- Consult Wind Resource Maps: As a first step, you can consult a wind resource map that is used to estimate the wind resource in your region. US Department of Energy’s WINDExchange has wind resource maps by state.
- Obtain Airport Wind Speed Data: Another way to indirectly quantify the wind resource is to get information about the average wind speed from a nearby airport. However, local terrain and other factors can cause the wind speed recorded at an airport to deviate from your location. Airport wind data is generally measured at heights of about 6 to 10 meters above the ground. The average wind speeds increase with height and, with a typical hub height of the wind turbine of 24 meters, can be 15 to 25% higher than with height measurements from airport anemometers.
- Observe Vegetation Flagging: Marking (the effect of strong winds on the area’s vegetation) can help determine the area’s wind speeds. Trees, especially conifers or evergreen trees, can be permanently deformed by strong winds.
- Use a Measurement System: Direct monitoring by a wind resource measurement system at a location provides the clearest picture of the available resource. Wind measurement systems are available for a cost of as little as $ 600 to $ 1,200. The gauges must be set high enough to avoid turbulence from trees, buildings, and other obstacles. The most useful readings are those measured at hub height, the height at the top of the tower where the wind turbine is to be installed.
- Obtain Data from a Local Small Wind System: If you have a small wind turbine near you, you may be able to get information about the annual performance of the system and, if necessary, wind speed data.
Zoning, Permitting, and Covenant Requirements
Before you invest in a small wind energy system, you should research potential zoning and neighborhood covenant issues.
You can find out about the zoning restrictions in your area by contacting the local building inspector, board of supervisors, and/or planning board. They can tell you if you will need to obtain a building permit and provide you with a list of requirements.
In addition to zoning issues, your neighbors or homeowners’ association might object to a wind machine that blocks their view. They also could be concerned about noise. Most zoning and aesthetic concerns can be addressed by supplying objective data.
Some general information about height and noise issues for home wind electric systems:
Height Issue: Some jurisdictions limit the height of structures that are allowed in residential areas, although variations are often possible. Most zoning ordinances have a height restriction of 35 feet.
Noise Issues: The sound level of most modern wind turbines in residential areas is slightly above the ambient wind noise. This means that while the sound of the wind turbine can be removed from the surrounding noise if conscious attempts are made to hear it, a residential-size wind turbine will not be a significant source of noise under most wind conditions.
For more information, see state and municipal codes and requirements for small renewable energy systems.
The Economics of a Small Wind Electric System
To help you analyze the economics of a small wind turbine and decide if wind power will work for you, there are a number of elements that you should estimate, including:
- Cash flow
- Electric bills and electric bill comparisons
- Wind characteristics
- Simple payback in years.
Finding these estimates can help determine whether wind power is a good option for your location. If it is taking too long to regain your capital investment, the number of years is getting too close to or longer than the wind energy life of the system. This is not practical for you.
Installing and Maintaining a Small Wind Electric System
When you’ve gone through the planning steps to evaluate whether a small wind turbine is working at your location, Now you will already have a general idea about:
- The amount of wind at your site
- The zoning requirements and covenants in your area
- The economics, payback, and incentives of installing a wind system at your site.
Now, it is time to look at the issues associated with installing the wind system:
- Siting or finding the best location for your system
- Estimating the system’s annual energy output and choosing the correct size turbine and tower
- Deciding whether to connect the system to the electric grid or not.
Installation and Maintenance
The manufacturer of your wind turbine or the dealer you bought it from should be able to assist you with installing your small wind turbine.
You can install the system yourself. However, before attempting the project, ask yourself the following questions
- Can I pour a proper cement foundation?
- Do I have access to a lift or a way of erecting the tower safely?
- Do I know the difference between alternating current (AC) and direct current (DC) wiring?
- Do I know enough about electricity to safely wire my turbine?
- Do I know how to safely handle and install batteries?
If you answered no to any of the above questions, you should probably choose to have a system integrator or installer install your system. Contact the manufacturer for assistance or contact your state energy office and local utility for a list of local system installers. You can also check the Yellow Pages for Wind Energy Providers.
A credible installer can provide additional services such as approval. Find out if the installer is a licensed electrician, ask for references and check them out. You can also contact the Better Business Bureau.
With proper installation and maintenance, a small wind electric system should last up to 20 years or longer. Annual maintenance can include:
- Checking and tightening bolts and electrical connections as necessary
- Checking machines for corrosion and the guy wires for proper tension
- Checking for and replace any worn leading edge tape on the turbine blades, if appropriate
- Replacing the turbine blades and/or bearings after 10 years if needed.
If you do not have the expertise to maintain the system, your installer may provide a service and maintenance program.
Siting a Small Electric Wind System
Your system manufacturer or dealer can also help you find the best location for your wind system. Some general considerations include:
1. Wind Resource Considerations
If you live in complex terrain, carefully choose the installation site. For example, if you set up your wind turbine on the top or on the windy side of a hill, you will have more access to the prevailing winds than in a gully or on the leeward side of a hill on the same property.
You can have different wind resources within the same property. In addition to measuring or determining the annual wind speeds, you also need to know the prevailing wind directions at your location. In addition to geological formations, you need to consider existing obstacles such as trees, houses, and sheds.
You also need to plan for future obstacles, such as: New buildings or trees that have not reached their full height. Your turbine must be out of the wind from buildings and trees and 30 feet above anything within 300 feet.
2. System Considerations
Make sure there is enough space to raise and lower the tower for maintenance. If your tower is guyed, you’ll need to leave room for the guy wires. Regardless of whether the system is stand-alone or on-grid, you also need to consider the length of the wire between the turbine and the load (house, batteries, water pumps, etc.).
A significant amount of electricity can be lost through wire resistance. The longer the wire runs, the more electricity is lost. Using more or larger cables also increases your installation costs. Your wire losses are greater when you have direct current (DC) instead of alternating (AC) current. If you have a long run of cables, it is advisable to convert direct current to alternating current.
Sizing Small Wind Turbines
Small wind turbines used in residential areas typically range in size from 400 watts to 20 kilowatts, depending on the amount of electricity you want to generate.
A typical home uses approximately 10,932-kilowatt hours of electricity per year (approximately 911 kilowatt-hours per month). Depending on the average wind speed in the region, a wind turbine in the 5 to 15-kilowatt range would be required to make a significant contribution to this demand.
A 1.5 kilowatt wind turbine meets the needs of a house that needs 300 kilowatt hours per month in a location with a 14 mile-per-hour (6.26 meters-per-second) annual average wind speed.
First, create an energy budget to determine what size turbine you will need. Since energy efficiency is typically cheaper than generating energy, reducing the amount of electricity your home uses is likely to be more cost effective and reduce the size of the wind turbine required.
The height of a wind turbine tower also affects how much electricity the turbine generates. A manufacturer should help you determine the tower height you need.
Estimating Annual Energy Output
An estimate of the annual energy output of a wind turbine (in kilowatt-hours per year) is the best way to determine whether it and the tower are producing enough electricity to meet your needs.
A wind turbine manufacturer can help you estimate the expected energy production. The manufacturer uses a calculation based on the following factors:
- Particular wind turbine power curve
- Average annual wind speed at your site
- Height of the tower that you plan to use
- Frequency distribution of the wind an estimate of the number of hours that the wind will blow at each speed during an average year.
The manufacturer should also adjust this calculation for the elevation of your site.
To get a preliminary estimate of the performance of a particular wind turbine, you can use the following formula:
AEO= 0.01328 D2 V3
- AEO = Annual energy output (kilowatt-hours/year)
- D = Rotor diameter, feet
- V = Annual average wind speed, miles-per hour (mph), at your site
Note: the difference between power and energy is that power (kilowatts) is the rate at which electricity is consumed, while energy (kilowatt-hours) is the quantity consumed.
Grid-Connected Small Wind Electric Systems
Small wind energy systems can be connected to the power distribution system. These are known as grid-connected systems. A grid-connected wind turbine can reduce the consumption of electricity for lighting, appliances and electrical heat.
When the turbine can’t deliver the amount of energy it needs, the utility company makes all the difference. If the wind turbine produces more electricity than your household needs, the excess is sent to the utility company or sold.
With this type of grid connection, your wind turbine will only work when the utility grid is available. In the event of a power failure, the wind turbine must be switched off for safety reasons.
Grid-connected systems can be practical if the following conditions exist:
- You live in an area with an average annual wind speed of at least 10 miles per hour (4.5 meters per second).
- Electricity from utility companies is expensive in your region (approx. 10–15 cents per kilowatt hour).
- The utility requirements for connecting your system to the grid are not prohibitively high.
There are good incentives for the sale of excess electricity or for the purchase of wind turbines. Federal regulations (specifically, the Public Utility Regulatory Policies Act of 1978, or PURPA) require utilities to connect with and purchase power from small wind energy systems. However, you should contact your utility before connecting to its distribution lines to address any power quality and safety concerns.
Your utility can provide you with a list of requirements for connecting your system to the grid. For more information, see grid-connected home energy systems.
Wind Power in Stand-Alone Systems
Wind energy can be used in off-grid systems, also known as stand-alone systems, that are not connected to a power distribution system or a power grid. In these applications, small wind electric systems can be used in combination with other components, including a small solar power system, to create hybrid power systems.
Hybrid power systems can provide reliable off-grid power to households, farms or even entire communities (e.g. a co-housing project) that are far from the nearest utility lines.
An off-grid hybrid electrical system can be useful for you if the following points describe your situation:
- You live in an area with an average annual wind speed of at least 9 miles per hour (4.0 meters per second).
- A grid connection is not available or can only be made through an expensive extension. The cost of running a power line to a remote site to connect with the utility grid can be prohibitive, ranging from $15,000 to more than $50,000 per mile, depending on terrain.
- You would like to gain energy independence from the utility.
- You would like to generate clean power.