Wind PowerFrequently Asked Questions :: Wind

(source: Windustry; NorthWestern Energy)

Wind Energy

Q: How much do wind turbines cost?
A: Wind turbines come in many shapes and sizes, but here is a rule of thumb on how much they cost:

  • Wind turbines have significant economies of scale. A large-scale wind turbine (i.e., greater than 600 kilowatts) costs approximately $1,000/kilowatt of nameplate capacity. That means a hypothetical 1,000 killowatt (1 megawatt) turbine will cost approximately $1 million full installed.
  • Smaller farm or residential scale turbines cost less overall, but are more expensive per kilowatt of energy producing capacity. Wind turbines under 100 kilowatts cost roughly $3,000 to $5,000 per kilowatt of capacity. That means a 10 kilowatt machine (the size needed to power an average home) might cost $35,000-$40,000.

See related Know Your Economics

Q: How big are wind turbines?
A:Wind turbines range in size from tiny micro turbines, to enormous utility scale power production facilities. Large turbines have rotor diameters of 50 to 90 meters. The tip of the blades might reach as high as 135 m (442 ft) in the air. Smaller turbines are usually placed on 30 to 40 meter towers. See Windustry's related graphic: The Scale of Wind Power.

Q: Are wind turbines noisy?
A: On a windy day, the sound of the turbine is drowned out by the wind even just a short distance from the turbine. Current technology makes noise almost a non-issue at most wind farms. However, wind turbines do produce some sound, which means wind farms should be sited with this in mind. Read more: PDF iconAmerican Wind Energy Association Fact Sheet: How Much Noise Do Small Wind Systems Make? and information from the British Wind Energy Association.

Q: Do wind turbines harm wildlife?
A: As with any large structure, wind turbines have the potential to harm birds. However, the actual number of birds that are killed each year by wind turbines is lower than you might imagine. According to the American Wind Energy Association, today's wind turbines pose far less of a threat to birds than radio towers, tall buildings, airplanes and vehicles and other man-made objects. Wind energy development will account for only a very small fraction of bird deaths caused by human activities. Summaries of available wind studies can be found at www.currykerlinger.com and at www.nationalwind.org.

Studies show that two to five birds per year, or less, are killed per wind turbine each year. Some sites record no bird deaths at all. “A reasonable, conservative estimate is that of every 10,000 human-related bird deaths in the U.S. today, wind plants cause less than one. Even if wind were used to generate 100% of U.S. electricity needs, at the current rate of bird kills, wind would account for only one of every 250,” says AWEA.

Q: Is wind energy expensive?
A: Wind energy is the cheapest form of new electricity generation available today. Wind power is more expensive than power from old, established power plants, but is cost competitive with any new power plant. Technology innovations and market building incentives have helped to dramatically lower costs over the last 20 years. Read more: AWEA's wind energy costs FAQ

Q: What is the status of the wind energy market in the United States?
A: Wind is the fastest growing energy source in the world, expanding at a rate of 20-30% per year. The U.S. had a record year for new wind in 2005, with more than 2,400 MW of new wind energy installations. This brings the national total to 9,149 MW of installed wind energy, enough to power 2.3 million homes. The outlook for U.S. growth in 2006 is bright as the industry in on course to bring over 3,000 new MW on-line over the year. California remains the nation-wide leader in installed capacity with 2,150 MW, but Texas is rapidly catching up with 1,995 MW. Iowa is in third place with 836 MW and Minnesota added 129 MW in 2005, putting us in fourth place with 744 MW. Minnesota continues to lead the country in community, farmer, and locally-owned wind projects.

Read more: Windustry Fact Sheet-Introduction to Wind Development.

Q: What is Net Metering and Net Billing?
A: The concept of net metering programs is to allow utility customers to generate their own electricity from renewable resources, such as small wind turbines and rooftop solar systems. The customers send excess electricity back to the utility when their wind system, for example, produces more power than needed. Customers can then get power from the utility when their wind system doesn't produce enough power. In effect, net metering allows the interconnected customer to use the electrical grid as a storage battery. This helps customers get higher (retail) value for more of their self-generated electricity. Read more: The Green Power Network: Net Metering Policies. See also Net Metering: NorthWestern Energy Net Metering Documents.

Q: What are the advantages and disadvantages of connecting my wind system to the utility grid?
A: The advantages of utility interconnection include having standard utility AC power when you need it, not just when the wind blows; eliminating the need for storing excess electricity in batteries, which can be expensive; and you only pay for the net electricity used. One disadvantage of net metering and net billing may be the cost of the interconnection, which can vary considerably from utility to utility. There are efforts to get standards in place for interconnection guidelines.

Q: Are there any investment opportunities in wind energy?
A: There are two broad classes of wind turbines: utility-scale and residential-scale. Most opportunities for public investment will be with the utility-scale turbines, as many of the industry participants are publicly-held corporations. These industry participants include wind developers who own the turbines and hold Power Purchase Agreements with utilities; the utilities or electric distribution companies that sell the electricity retail to customers; transmission companies; energy marketers; turbine installation contractors; and turbine, tower, and other related hardware manufacturers. Some of these companies are listed on Windustry's Resources page. You should consult an investment advisor that specializes in the energy industry. A new development in the investment profession is that a growing number of advisors, managers and mutual funds are specializing in environmentally-benign investment opportunities. A business library can also help you find references to these opportunities. Read more: PDF iconAmerican Wind Energy Association Investment Fact Sheet.

Q: How do I lease my land to wind turbine developers?
A: Wind developers buy the turbines from the manufacturers, lease the land to place the turbines, construct and operate the development, and sell the electricity to a utility or distribution company. As a landowner, your business role will be to negotiate a contract for the lease of your land to a wind developer. To prepare for this, you need to understand your product (your land) and market it to your customer (the wind developer). Wind developers are looking at more than just a strong wind resource, though. They are also looking at the availability of transmission lines, the amount of open space, and a host of other factors. In reality, if a developer is interested in your land to host a project, they will contact you. Wind developers assume that land owners have not performed any preparatory analysis of their land. They choose sites based upon their own analysis methods. When they have located suitable sites, they contact the land owner to negotiate a lease. Sometimes before deciding on the land they will ask the landowner if they can perform their own analysis of the site, including installing an anemometer (wind measuring instrument). If you think you have a sufficient understanding of your land and your wind resource, you can invite conversations with developers. Wind developers range from large, multi-national wind turbine manufacturers to small regional businesses. Some are listed on Windustry's Resources page.

Q: How do I measure the wind resource on my land?
A: Wind assessment takes place at a number of different levels: consulting a wind map, obtaining previously measured data, and taking your own measurements. The cheapest and easiest way to assess your resource is to consult a wind map. It is important, however, to remember that wind maps are not always detailed to the level of individual homesteads and there are many factors, such as hills, buildings, and trees that may further cause variances from the map. Nevertheless, it is a good place to start to give a general idea of your resource and do some basic economic analysis. The next step is to obtain data that has already been measured by other groups in your area. Airports, for example, keep track of wind speeds in their area.The Montana Department of Environmental Quality (DEQ) also gathers wind speed data for public lands. Finally, you can measure your own wind speed by installing a device called an anemometer.

Q: Will a wind energy system reduce my power bills?
A: Yes, but the amount of savings depends on the size of the system and the amount of solar potential at the site, especially if efficiency measures are included. Adding insulation, changing to compact fluorescent lights, and replacing old appliances with high-efficiency models can dramatically lower your power bills. Many customers are able to watch their electricity meters run backwards as their homes deliver electricity back to the utility sytem at times when their own eneryg needs are low. For more information on ways to increase your home's energy efficiency, see:

Q: Are hybrid systems that use both PV and wind available?
A: Yes. Hybrid systems are configured on the type and size of the individual applications. The theory behind hybrid systems is to combine resources and to provide power during time periods when either the wind isn't blowing or the sun isn't shining. On a cost basis in a net-metered application, hybrid systems aren't as practical as in a battery storage application. For more information, see DOE's Small Hybrid Solar and Wind Electric Systems.

Q: Can I both net meter a system and use batteries?
A: Yes. Some customers who want security and a "back-up" in the case of possible emergencies and outages can install additional components that provide power to batteries. The extra components include batteries, a battery charge controller, and separate subpanel(s) for critical load circuits. The number of appliances the homeowner wants to power in the event of a blackout dictates the additional expenses of the system. In the case of NorthWestern Energy, additional components and safeguards to prevent transfer of power to the utility grid are required and will be validated prior to hook-up.

Q: How do I perform a cost analysis for a system?
A: There is no finite answer for how to perform a cost analysis that is 100% accurate. However, customers should either base their analysis on present values or on predicted values (on both sides of the equation). For simplicity purposes, if calculating payback on a system using present values, the equation would include the cost of your current electricity bill (adjusted at 3% inflation per year). In this case, if the system was being financed, interest also would have to be included. However, as customers realize, the production costs of electric energy have undergone several large increases in recent history. This is not a controllable variable for NorthWestern Energy, and the future price for residential electricity is uncertain. With a home renewable energy system, cost spikes would be of less importance because, although the electricity that would need to be purchased by the homeowner would be indicative of the current market price, the power transferred back to the utility would also be accounted for at the current wholesale market price.

Q: With all the ratings, capacity factors, and differing inputs regarding the amount of output I can expect, what is a realistic, attainable production number?
A: Although all of the variables do become confusing, and sometimes different opinions originate from different perspectives, the majority of research and data suggest the 7-18% of rated capacity amount as a reasonable figure for Montana PV and small wind applications. This is a "bottom line" number and assumes that you are purchasing and installing a reputable generator and system components.

Q: Is there any maintenance involved with having a wind grid-intertie system?
A: If your system does not have a battery back-up, then any manufacturer-recommended maintenance is minor. (Some wind-power manufacturers suggest with a wink that you should go out once a year to inspect your blades; if they're turning, you've completed your maintenance.) We suggest that you alsways follow the manufacturer's recommendations.


Q: How would I have a wind turbine installed at my home?
A: Most dealers offer either complete turnkey (ready-to-operate) installations or the option to purchase direct from the factory and install the system yourself. The first option offers more customer support from the company. Self-installation offers significant savings and a hands-on understanding of the turbine. Prospective owners can discuss the options available with manufacturers to decide which method best suits their budget and technical skills . See the list of Montana renewable energy dealers. (Source: American Wind Energy Association).

Q:What is commercial (large) scale wind?
A: Commercial scale wind refers to wind energy projects greater than 100 kW. Typically, the electricity is sold rather than used on-site. This category can include large arrays of 100 or more turbines owned by large corporations or a single locally-owned wind turbine greater than 100 kW in size. (Source: windustry.org)

Q: What is community wind?
A: Community wind projects are locally owned by farmers, investors, businesses, schools, utilities, or other public or private entities and they optimize local benefits. The key feature is that local community members have a significant, direct financial stake in the project beyond land lease payments and tax revenue. Projects may be used for on-site power or to generate wholesale power for sale, usually on a commercial-scale greater than 100 kW.

If you are interested in starting a community wind project, check out Windustry.org's Community Wind Toolbox to help guide you along the process.

Q: How much electricty can one wind turbine generate?
A: The ability to generate electricity is measured in watts. Watts are very small units, so the terms kilowatt (kW, 1,000 watts), megawatt (MW, 1 million watts), and gigawatt (pronounced "jig-a-watt," GW, 1 billion watts) are most commonly used to describe the capacity of generating units like wind turbines or other power plants.

Electricity production and consumption are most commonly measured in kilowatt-hours (kWh). A kilowatt-hour means one kilowatt (1,000 watts) of electricity produced or consumed for one hour. One 50-watt light bulb left on for 20 hours consumes one kilowatt-hour of electricity (50 watts x 20 hours = 1,000 watt-hours = 1 kilowatt-hour).

The output of a wind turbine depends on the turbine's size and the wind's speed through the rotor. Wind turbines being manufactured now have power ratings ranging from 250 watts to 5 megawatts (MW).

Example: A 10-kW wind turbine can generate about 10,000 kWh annually at a site with wind speeds averaging 12 miles per hour, or about enough to power a typical household. A 5-MW turbine can produce more than 15 million kWh in a year--enough to power more than 1, 400 households. The average U.S. household consumes about 10,000 kWh of electricity each year. (Source: American Wind Energy Association)

Q: What are the advantages and disadvantages of wind energy?
A:

A Renewable Non-Polluting Resource

Wind energy is a free, renewable resource, so no matter how much is used today, there will still be the same supply in the future. Wind energy is also a source of clean, non-polluting, electricity. Unlike conventional power plants, wind plants emit no air pollutants or greenhouse gases. According to the U.S. Department of Energy, in 1990, California's wind power plants offset the emission of more than 2.5 billion pounds of carbon dioxide, and 15 million pounds of other pollutants that would have otherwise been produced. It would take a forest of 90 million to 175 million trees to provide the same air quality.

Cost Issues

Even though the cost of wind power has decreased dramatically in the past 10 years, the technology requires a higher initial investment than fossil-fueled generators. Roughly 80% of the cost is the machinery, with the balance being site preparation and installation. If wind generating systems are compared with fossil-fueled systems on a "life-cycle" cost basis (counting fuel and operating expenses for the life of the generator), however, wind costs are much more competitive with other generating technologies because there is no fuel to purchase and minimal operating expenses.

Environmental Concerns

Although wind power plants have relatively little impact on the environment compared to fossil fuel power plants, there is some concern over the noise produced by the rotor blades, aesthetic (visual) impacts, and birds and bats having been killed (avian/bat mortality) by flying into the rotors. Most of these problems have been resolved or greatly reduced through technological development or by properly siting wind plants.

Supply and Transport Issues

The major challenge to using wind as a source of power is that it is intermittent and does not always blow when electricity is needed. Wind cannot be stored (although wind-generated electricity can be stored, if batteries are used), and not all winds can be harnessed to meet the timing of electricity demands. Further, good wind sites are often located in remote locations far from areas of electric power demand (such as cities). Finally, wind resource development may compete with other uses for the land, and those alternative uses may be more highly valued than electricity generation. However, wind turbines can be located on land that is also used for grazing or even farming. (source: Argonne National Lab)

Q: Do wind turbines pose a safety hazard?
A: Unlike most other generation technologies, wind turbines do not use combustion to generate electricity, and hence don't produce air emissions. The only potentially toxic or hazardous materials are relatively small amounts of lubricating oils and hydraulic and insulating fluids. Therefore, contamination of surface or ground water or soils is highly unlikely. The primary health and safety considerations are related to blade movement and the presence of industrial equipment in areas potentially accessible to the public. Like all electrical generating facilities, wind generators produce electric and magnetic fields. For more information on wind energy and wind energy development, visit ANL's Wind Energy Guide.

Q: How are commercial wind farms developed and how can I get a wind farm on my property?
A:Commercial wind farms are built by wind energy developers using private sources of financing. Before installing turbines, the developer will assess the wind resource at a particular site by collecting meteorological data, determining access to transmission lines, and considering environmental and community impacts. If sufficient wind resources are found, the developer will secure land leases from property owners, obtain the necessary permits and financing, and purchase and install wind turbines. The completed facility is often sold to an independent operator (called an independent power producer) who generates electricity to sell to the local utility, although some utilities own and operate wind farms directly. (Source: DOE)

Q: How can I find a job in the wind industry?
A: The American Wind Energy Association (AWEA), the trade association for the wind industry, has a website on careers in the wind industry that includes job postings from its members and other companies working in the industry. EERE also maintains a list of web sites that post clean energy jobs.

Q: What equipment do I need to run my own home wind energy system?
A: All wind systems consist of a wind turbine, a tower, wiring, and the "balance of system" components: controllers, inverters, and/or batteries. Hybrid systems use additional equipment, like photovoltaic panels and diesel generators to ensure electricity is available at all times.

Wind Turbines

Home wind turbines consist of a rotor, a generator mounted on a frame, and (usually) a tail. Through the spinning blades, the rotor captures the kinetic energy of the wind and converts it into rotary motion to drive the generator. Rotors can have two or three blades, with three being more common. The best indication of how much energy a turbine will produce is the diameter of the rotor, which determines its "swept area," or the quantity of wind intercepted by the turbine. The frame is the strong central axis bar onto which the rotor, generator, and tail are attached. The tail keeps the turbine facing into the wind.

A 1.5-kilowatt (kW) wind turbine will meet the needs of a home requiring 300 kilowatt-hours (kWh) per month, for a location with a 6.26-meters-per-second (14-mile-per-hour) annual average wind speed. The manufacturer will provide you with the expected annual energy output of the turbine as a function of annual average wind speed. The manufacturer will also provide information on the maximum wind speed in which the turbine is designed to operate safely. Most turbines have automatic speed-governing systems to keep the rotor from spinning out of control in very high winds. This information, along with your local wind speed distribution and your energy budget, is sufficient to allow you to specify turbine size.

Towers

To paraphrase a noted author on wind energy, "the good winds are up high." Because wind speeds increase with height in flat terrain, the turbine is mounted on a tower. Generally speaking, the higher the tower, the more power the wind system can produce. The tower also raises the turbine above the air turbulence that can exist close to the ground. A general rule of thumb is to install a wind turbine on a tower with the bottom of the rotor blades at least 9 meters (30 feet) above any obstacle that is within 90 meters (300 feet) of the tower.

Experiments have shown that relatively small investments in increased tower height can yield very high rates of return in power production. For instance, to raise a 10-kW generator from a 18-meter (60-foot) tower height to a 30-meter (100-foot) tower involves a 10% increase in overall system cost, but it can produce 25% more power.

There are two basic types of towers: self-supporting (free standing) and guyed. Most home wind power systems use a guyed tower. Guyed-lattice towers are the least expensive option. They consist of a simple, inexpensive framework of metal strips supported by guy cables and earth anchors.

However, because the guy radius must be one-half to three-quarters of the tower height, guyed-lattice towers require enough space to accommodate them. Guyed towers can be hinged at the base so that they can be lowered to the ground for maintenance, repairs, or during hazardous weather such as hurricanes. Aluminum towers are prone to cracking and should be avoided.

Balance of System

Stand-alone systems require batteries to store excess power generated for use when the wind is calm. They also need a charge controller to keep the batteries from overcharging. Deep-cycle batteries, such as those used to power golf carts, can discharge and recharge 80% of their capacity hundreds of times, which makes them a good option for remote renewable energy systems. Automotive batteries are shallow-cycle batteries and should not be used in renewable energy systems because of their short life in deep cycling operations.

In very small systems, direct current (DC) appliances operate directly off the batteries. If you want to use standard appliances that require conventional household alternating current (AC), however, you must install an inverter to convert DC electricity to AC. Although the inverter slightly lowers the overall efficiency of the system, it allows the home to be wired for AC, a definite plus with lenders, electrical code officials, and future homebuyers.

For safety, batteries should be isolated from living areas and electronics because they contain corrosive and explosive substances. Lead-acid batteries also require protection from temperature extremes.

In grid-connected systems, the only additional equipment is a power-conditioning unit (inverter) that makes the turbine output electrically compatible with the utility grid. No batteries are needed. Work with the manufacturer and your local utility on this.

Hybrid Systems

According to many renewable energy experts, a stand-alone "hybrid" system that combines wind with photovoltaic (PV) technologies and/or a diesel generator offers several advantages.

In much of the United States, wind speeds are low in the summer when the sun shines brightest and longest. The wind is strong in the winter when there is less sunlight available. Because the peak operating times for wind and PV occur at different times of the day and year, hybrid systems are more likely to produce power when you need it.

For the times when neither the wind generator nor the PV modules are producing electricity (for example, at night when the wind is not blowing), most stand-alone systems provide power through batteries and/or an engine-generator powered by fossil fuels like diesel.

If the batteries run low, the engine-generator can be run at full power until the batteries are charged. Adding a fossil-fuel-powered generator makes the system more complex, but modern electronic controllers can operate these complex systems automatically. Adding an engine-generator can also reduce the number of PV modules and batteries in the system. Keep in mind that the storage capability must be large enough to supply electrical needs during noncharging periods. Battery banks are typically sized for one to three days of windless operation. (Source: DOE EERE)

 

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