Basic Questions
What is a wind turbine?
A wind turbine is energy system that transforms kinetic energy of the wind into mechanical or electrical energy that can be harnessed for practical use. Mechanical energy is most commonly used for pumping water in rural or remote location. Wind electric turbines generate electricity for homes and businesses and for sale to utilities.
How many homes can one megawatt of wind energy supply?
An average U.S. household uses about 10,000 kilowatt-hours (kWh) of electricity per year. One megawatt of wind energy can generate between 2.4 million and 3 million kWh annually. Therefore, a megawatt of wind generates about as much electricity as 240-300 average U.S. households use.
Why use wind energy?
Wind Energy is a clean, renewable, and domestic source of energy. While the wind may change day to day, it stays consistent from year to year. By harnessing this energy, we are replacing fuels with the free fuel of wind. In many states across the country, this is enabling utilities and customers to save dollars and harmful emissions.
How much wind is in Tennessee?
According to the Tennessee Valley Authority's Renewable Energy Assessment in 2008, there is approximately 8,000 gigawatt hours (GWh) of potential wind energy in the state. This does not include environmentally sensitive lands such as the Great Smoky Mountains National Park. If all of this electricity was fully harnessed it would be enough to power 800,000 average U.S. households. A good comparison is that according to TVA, hydropower dams account for 9,900 GWh of electricity in the TVA region. So, there is nearly as much wind energy available as hydropower currently being used.
What is my wind resource?
While wind varies from location to location, there are some basic assumptions that can be made when trying to assess your wind resource. In the state of Tennessee the wind tends to blow stronger and more consistent at higher elevations. Elevations above 1500', and certainly above 2000' , are likely to contain strong enough winds to justify the installation of a small wind turbine. Higher elevations, typically over 3000', are likely to contain strong enough winds to justify the installation of a large wind turbine.
Since wind varies throughout the state of Tennessee, the Tennessee Wind Working Group encourages you to consult a wind map of the state. If you think that you may meet the conditions described above for a wind energy system, please do not hesitate to contact us.
Price and Effectiveness of Energy
How long does it take for a wind turbine to pay itself off?
The amount of power a wind turbine produces is directly related to how often, and strong, the wind blows. The more often a strong wind blows, the more power a wind turbine will produce. Also, since wind turbines come in various shapes, it is difficult to determine a general pay back period for turbines. Please contact the Tennessee Wind Working Group for any clarifying questions
If wind is competitive, why does it need a tax credit subsidy from the government?
The energy market has never been free of government subsidies -- large energy producers such as coal, oil, and nuclear have always been able to win government subsidies of various kinds. To take just one example, the federal government has paid out $35 billion over the past 30 years to cover the medical expenses of coal miners who suffer from "black lung disease." These subsidies mean that the true cost of coal is not reflected in its market price.
The wind Production Tax Credit was passed by Congress to give wind a "level playing field" compared to long subsidized energy sources.
I've heard in Denmark, they are no longer installing wind turbines, is this because wind is a failure?
No. Denmark currently has wind supply over 25% of its electricity to its citizens. It must be understood that Denmark is a much smaller country than the United States (approximately half the size of Indiana). This means that even though Denmark has high levels of penetration, they have less wind energy installed that currently exists in the United States. Furthermore, since the United States, and Tennessee, are larger than Denmark, our electrical grids can accommodate more wind energy because while the wind may slow down in Chattanooga, that does not mean it has quit blowing in Mountain City. This geographic diversity leads to grid balance and reliability.
Operational
Since the wind doesn't blow all the time, doesn't that mean it is unreliable?
No. While utilities generally prefer plants that can generate as needed (conventional plants) to plants that cannot (such as wind plants), this does not mean that wind plants are unreliable. Utilities must forecast each day how much electricity to have available for customers based on demand, which is effected by climate. As concerns about emissions, rising fuel costs, and national security continue to rise, many utilities across the nation are beginning to apply forecasting to not only electricity demand, but also wind forecasting. By understanding the amount of wind energy that will be available for the next day, utilities are able to plan there other resources around the wind energy forecast.
One good way to "firm" up wind energy, or help with slight variations in its forecast, is to have a substantial amount of hydropower integrated onto the grid system. In the state of Tennessee, we are fortunate the Tennessee Valley Authority has a very well integrated hydropower system, the foundation of the TVA in the 1950s.
If a wind turbines capacity factor is 33%, doesn't that mean it blows 1/3 of the time?
No. The wind turbines at TVA's Buffalo Mountain wind site produce electricity between 65-90% of the time. However, much of that time these turbines are generating at less than full capacity, making its capacity factor lower.
What is an availability factor?
Availability factor is a measurement of the reliability of a wind turbine or other power plant. It refers to the percentage of time a plant is ready to generate (that is, not out of service for maintenance or repairs). Modern wind turbines have availability of more than 98%--higher than most other types of power plants. After nearly three decades of constant engineering refinement, today's wind machines are highly reliable.
Environmental Questions
How loud are wind turbines?
Noise was an issue with some early wind turbine designs, particularly during the 1980s and early 1990s. These issues have been largely eliminated as a problem through improved engineering and through appropriate use of setbacks near residents. Aerodynamic noise has been reduced by adjusting the thickness of the blades' trailing edges and by orienting blades upwind of the turbine tower. A small amount of noise is generated by the mechanical components of the turbine. To put this into perspective, a wind turbine 250 meters from a resident is no noisier than a kitchen refrigerator.
What about turbines throwing blades, or ice?
Blade throws were common in the industry's early years, 1980s, but are unheard of today because of better turbine design and engineering. Ice throw has been studied by national laboratories and found to be of little danger because of setbacks typically required to minimize noise.
What about visual impacts? Won't wind turbines lower my property value?
Through careful design of a wind power plant, aesthetic impacts can be minimized. In the early years of wind projects, turbines of different size and designs were used throughout the wind farm. Today, most wind farms have turbines that are properly spaced, used the same machine, and here in Tennessee will be spaced along a ridge top. Computer simulations help citizens understand how the viewshed may change, and public opinion polls show that the vast majority of people favor wind energy. Regarding property values, Lawrence Berkeley National Laboratory has conducted the only peer reviewed study of real life data surrounding wind farms along the East Coast. Using thousands of sample statistics the study concluded that there was no statistical significant impact to the value of a home due to the construction of a wind project, either increasing the value or decreasing the value.
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