- What is the motivation behind your wind project?
- Small wind economics
- Knowing your wind resource
- Choosing a turbine, tower and other equipment
- Choosing an installer
- Working with your utility
- Net metering
- Operations and maintenance
This is the first question you should ask yourself before undertaking a small wind installation. Some people chose to put up their own turbines for environmental reasons, because wind energy is a clean, emission free, renewable energy source. Many like the idea of being energy independent, while others are tinkerers wishing to incorporate their energy consumption into their love of machines and technology. Whatever your motivation you should understand what is involved in owning your own wind generator as they are sophisticated pieces of machinery that will need periodic maintenance and can be a fairly large investment.
Your motivation for planning a small wind project will affect your choice of equipment, the economics of your project, and how you choose to operate and maintain your small wind system.
At the beginning of planning your project keep the following questions in mind:
- What will the energy be used for? Some people have off-grid systems where all of the energy used on the site must be generated there. Most will choose to connect their system to the utility's system and use the grid for backup energy when the wind does not blow. Others wish to sell energy back to the utility to provide supplemental income for their farm or business.
- Will the system offset some or all of the energy consumed on site? If this is the case, your state may have net metering laws which can help with the economics of your project but may limit the size of your system.
- Do I want to sell the energy to the utility? If you want to sell most or all of your energy to the utility this will affect the scale and financing of your machine. Larger machines generally can produce energy at a lower cost than small machines and will improve the return on investment. If selling power to the utility and making money is a primary motivation, then you may want to consider investing in a commercial scale wind project over a small wind system.
- Is cost of energy important to your project? Are your primary motivations environmental or energy independence? Cost of energy will greatly affect the components you choose. A general rule is that as system size increases the cost per installed kW will decrease, improving the economics of the project. If you are on a limited budget or want to size your system so that it matches up to your electricity consumption for an off grid system you will choose system components using a different set of assumptions.
- What is the budget for your system? Budget is in many cases the limiting factor for small wind systems. Because the return on investment is generally low compared to a commercial scale turbine the system must be able to fit within your family or business's budget to make sure you can afford to make payments on any loans taken to finance the system.
For a small wind system determining the payback of a project plays a large factor in determining if owning your own system makes sense for you. In order to do this you will need several pieces of information:
- a reasonable estimate of the wind resource at your site
- the height of the tower
- the turbine model's power curve (can be obtained from the manufacturer)
- the installed cost of the system
- annual costs that include maintenance, added insurance, fees paid to the utility, etc.
- the cost of energy at your site as well as historical electricity consumption on a monthly basis, if available.
- information from your utility about system size limits, net metering structure and rate for compensation for energy sold back to the utility
- interest rate on loan for equipment purchased
- information about grants and incentives available to you
Typically, for a small wind system, energy produced is used to offset a portion or all of the electricity at a site. Excess generation is then "stored" on the grid for times when the generator is not producing. At the end of the billing period the net excess generated or consumed is used to determine how much you owe the utility or the utility owes you. The rate and rules for compensation differ from state to state. To find out the rules for net metering in your state visit the Database of State Incentives for Renewables and Efficiency.
Once you determine how energy is compensated, the estimated production on a monthly basis and the installed and ongoing costs of the turbine, the payback period can be determined by dividing the sum of the costs by the net energy produced times the rate compensated for energy.
# years = (sum of installed costs and ongoing costs)/
[(energy produced) x (rate compensated for energy)]
This will yield the number of years it will take to pay off the machine. This calculation is called a simple payback because it does not take into account net present value, inflation, and escalation of energy costs over time. In most cases this method will be more conservative than a more involved analysis.
There are tools to help potential wind turbine owners determine the economic viability of their project. The Wind Powering America Wind Energy Payback Workbook is a spreadsheet tool that can help you analyze the economics of a small wind electric system and decide whether wind energy will work for you (MS Excel 102 kB). For Minnesotans, Windustry has developed a small wind calculator that compares 3 well-regarded turbines of different sizes, includes assumptions about pricing as of 2012, and incorporates Minnesota's net metering law.
The first step to designing your system is determining if you have enough wind to justify the expense of the system and the time and expense of operating and maintaining your equipment. Remember: a small turbine without enough wind is like a solar panel in the shade: it won't produce energy!
Generally, a site with an annual average wind speed of 12 miles per hour or greater does not need a detailed wind resource study to be performed. A site with an average wind resource of 10 miles per hour or less usually does not have enough wind to justify installing a turbine. A site that has an average wind speed between 10 and 12 miles per hour should have a wind resource assessment performed to determine if there is adequate wind to support a small wind turbine.
In general a good place to begin determining your wind resource is National Renewable Energy Laboratory's (NREL) wind resource maps. Download the map for your state and find the general area where your property is located. This will give you a fairly good sense of the average wind speed in your area at no expense.
If you are in Minnesota, the state Department of Commerce, Energy Division, provides an excellent interactive tool that provides an estimate of the average wind speed 100 feet up for any point in the state.
Airports also take regular meteorological data. If there is an airport in your area, contact them and ask them for wind data. State-specific consumer guides can also be found at the Department of Energy's Energy Efficiency and Renewable Energy website. For further information from Windustry on wind resource assessment, visit our Know Your Wind page.
A typical wind energy system consists of the turbine itself mounted on top of a tower and a controller consisting of power electronics which controls the power output of the turbine under various wind and grid conditions. Typically a controller will come as part of a package with the turbine making turbine and tower the major decisions in choosing your system. There are many different turbine manufacturers with many models of turbines to chose from as well as several tower configurations that vary in difficulty for erecting.
Choosing a small wind turbine model
Wind turbines come in many different makes and models. Spending a little extra time while choosing a model will improve economics of your project as well as make it much more successful in the long run.
Before choosing a turbine you should figure out if the electricity produced will be consumed completely on site, if you want to sell excess energy back to the utility company or if you prefer to be off the grid. The turbine model you choose will be greatly affected by where the electricity will ultimately be used and what compensation you will receive from selling electricity back to the utility. If your facility will be net metered or off the grid a load analysis for your home should be done to determine your monthly electricity usage, for net-metering, or your peaking load and daily usage for off grid applications.
Turbine manufacturers have published power curves that estimate the monthly output for their turbines based on average wind speed at the site and the Rayleigh distribution of wind speeds around that average.
Home Power Magazine is a good resource for comparison of small wind turbines. See the following articles on their website: "Apples & Oranges: Choosing a Home-Sized Wind Generator" and "Wind Generator Buyer's Guide."
Vertical Axis Wind Turbines (VAWTs)
Vertical axis wind turbines (they look like egg beaters) have been around longer than horizontal axis wind turbines (the most common type of wind turbine). Some vertical axis turbines have been very effective at producing energy. The concern for consumers is that many manufacturers of vertical axis wind turbines make inflated or fraudulent claims about the technology.
No matter what anyone says, vertical axis wind turbines still need to be placed on tall towers for ground clearance. Wind turbines are placed on tall towers because the wind speeds are higher and there is less turbulence higher above the ground, producing greater energy yield.
Some claim that vertical axis wind turbines are more efficient and operate in lower wind speeds than horizontal axis wind turbines. Modern horizontal axis wind turbines are actually better at capturing the wind than vertical axis machines given the same amount of swept area (which is the size of the circle traced by the outside tip of the blades). This is because vertical axis machines always have at least one blade traveling into the wind creating additional drag on the machine as it spins. Additionally, neither horizontal nor vertical axis of machines will produce much energy in low wind speeds because there is little energy to capture from low-speed wind.
Vertical axis wind turbines should not be mounted on rooftops, even if that makes them easy to install. Buildings and other obstructions will create turbulence in the wind as well as decrease its speed, significantly reducing the wind turbine’s ability to produce energy, even for a vertical axis turbine.
For further information about Vertical Axis Wind Turbines:
- Robert Preus – Thoughts on VAWTs: Vertical Axis Wind Generator Perspectives from issue 104 of Home Power magazine
- Mick Sagrillo – The Myths & Mysticism of Vertical Axis Wind Turbines
Buyers should beware of used, refurbished, or remanufactured machines. Even though these machines may initially be less expensive that comparable new machines, the initial savings can be negated very quickly by costly repairs from a machine that is nearing the end of its life time. Before purchasing a used machine read through this article by Mick Sagrillo from the November 2002 American Wind Energy Association newsletter about buying used wind equipment.
Choosing a Tower
Small wind system manufacturers often give you several different tower options to best match the economic, maintenance and space needs of your project.
There are four basic types of tower options for home and farm sized turbines: guyed monopole, guyed lattice, (self-supporting) lattice and (self-supporting) monopole.
Guyed Monopole: this type of tower is generally the least expensive. The tower is a tilt-up style tower and is generally installed using a gin-pole and winch. Guyed monopoles generally have 4 guy wires for support. Maintenance on the turbine is performed by tilting the tower down. The height of this type of tower is limited by the weight of the machine and generally 10 kW machines are the largest that can be placed on such towers. Tilt up towers require much space for guy wires and for tipping up and down of the tower. Check with manufacturers to determine what type of tower they recommend with particular turbine models.
Guyed lattice towers are generally more expensive than monopole designs but can support larger turbines at higher heights. Towers are generally installed using gin-pole and winch. Guyed lattice towers also come with the advantage of either being able to tip the tower down or relatively easy climb-ability for regular maintenance (climbing, if done with appropriate safety precautions, gear and training, is much safer than tilting a tower up and down every time maintenance is required). Guyed lattice towers require much space for tipping up and down of tower and guy wires. Again, check with turbine manufacturers to see what tower options they recommend with various turbine models.
Lattice towers, in most cases, are required for machines larger than 20 kW in size. The installation cost of these towers is generally more than that of a guyed lattice tower because a crane is needed to lift the tower and turbine into place. Maintenance is performed by climbing the tower. If major work is required on a machine a crane may be required to remove the turbine from the tower.
Monopole towers are generally regarded as the most aesthetically pleasing, but they also tend to be the most expensive and so tend to be used only with machines rated 10kW or more. All utility scale turbines are put on monopole towers. Check with your turbine manufacturer to determine what tower options they recommend with your turbine model.
Choosing an installer for your wind turbine and other related equipment is as important if not more so than choosing the equipment for your system. Before choosing an installer read through and understand What to Expect From Your Renewable Energy Dealer, written by Richard Perez and published in Home Power Magazine in 2001.
A good installer will have installed many wind projects and have a good track record with those in the wind energy community. Before deciding on an installer ask the installer if you can contact other people he or she has done work for. A good installer will work with you as you design your equipment and work closely with the interconnecting utility to ensure that the process goes smoothly.
Make sure that your installer is a licensed and bonded electrician, or that the person doing the electrical work is licensed or bonded as an electrician. Otherwise, the electrical inspector may not sign off on the work after it is completed. For more complete information about what is required for lelctrical certification for an installer contact your utility.
Windustry has a list of Midwest dealers/installers of home and farm sized wind energy systems elsewhere on our site. Disclaimer: Windustry does not endorse or recommend any of the dealers contained on this list. Consumers are advised to perform due diligence in selecting a renewable energy dealer for their project by contacting former customers of the installer as well as seeking recommendations from persons experienced with home and farm sized turbines.
To have a successful grid connected project you have to work with the utility to make the interconnection go smoothly. Get the utility involved early in the process of planning. Many times your utility will have a dedicated contact for systems of this size range. They will also have technical interconnection standards for your equipment and special meters which may need to be installed at your service. You will also need to have a state electrical inspector sign off on your system before the utility will allow you to connect to the grid. The inspector will require that all electrical work, wiring and otherwise, be completed by a licensed and bonded electrician.
Click here to go to a directory of contact information for many midwestern utilities.
Before putting your project in the ground you will have to acquire the appropriate permits from your county zoning office or municipal zoning office. Many areas that have seen much wind energy development in recent years may have zoning ordinances designed specifically for smaller wind projects. If this is not the case you may have to obtain a special use permit from the county zoning board.
Having other small wind turbines in the area may make the process easier. However, you may have to be persistent with with the process because zoning board members may associate your proposed project with its larger utility scale cousins.
The issues that you will have to address while going through the zoning process include:
- Setbacks from property lines, structures, roads, river beds, etc.
- Safety standards for tower and electrical equipment and wiring, including proper grounding of turbine and tower
- Aesthetics of tower and turbine design
- Interference with electro-magnetic telecommunications
A small wind machine needs to carry insurance to protect the equipment, just like any other large investment you make. If a once in one hundred year storm destroys the machine, liability insurance is important to protect yourself, others and the interconnecting utility against unforeseen circumstances. Some states, such as Minnesota, mandate that the machine have a certain amount of liability insurance, while in other states utilities set their own requirements for insurance.
Mick Sagrillo, a seasoned installer and wind energy advocate from Wisconsin put together a three-piece series on insuring small wind systems, which you can read by clicking here.
Net metering is a way for you to connect your small wind turbine behind the meter at your home, business or farm. This system is designed to allow energy generated at your home farm or business to offset some or all of the electricity you use. If your generator is producing more electricity than you can consume the excess is sold back to the utility. The price that a project receives for the excess electricity varies from state to state and from utility to utility. Net metering can be very helpful for the economics of a wind project because it allows a qualifying facility to receive retail rate for a portion or all of the electricity generated. Currently more than 35 states and the District of Columbia have net metering programs requiring utilities purchase power from systems that qualify for the program. Each state has different rules and regulations. To find out if net metering is available in your state, what systems qualify and how to take advantage of the programs visit the Database of State Incentives for Renewable Energy.
Here are a few good resources for more information about net metering:
In a good year at a good wind site, a small turbine might be running 6,000 hours over the course of a year. For comparison, this is about the same as driving your car 200,000 miles! Not suprisingly, your small turbine will last longer and perform better if maintenance is done regularly. For most systems, you should plan to either tilt down the tower or climb the tower once a year to check for signs of unusual wear, tighten bolts, lubricate moving parts and perform other general maintenance. You should check with the manufacturer or dealer of your turbine for specific guidelines, or contract with your installer for future maintenance.