Figure 1. Searsburg Wind Energy Facility, Searsburg, VT (RAEL, 2002)
Clean energy for America is the wave of the future. Harnessing the earth's wind has become a growing resource for today's clean energy market. Wind powered energy offers countless environmental and public health benefits. Advanced technologies in this field are bringing costs down for consumers to consider wind as a resource. Wind farm production for energy also brings economic opportunities to rural areas where they are needed the most. To use wind for power and electricity in America is the answer to a cleaner, more efficient future.
Wind powered energy is the use of special wind turbines to create a clean, emission free energy source. This natural energy source is driven by temperature differences. The earth's oceans have a much higher heat capacity than the landmasses. This difference causes high pressure gradients resulting in strong winds. Harnessing this wind for our energy needs is the ultimate goal in wind energy. Wind is harnessed through a pocket of low pressure that forms on the underside of a turbine's blade. "This pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag (NREL)." The combination of the two causes rotation of the turbine which generates electricity from the inner generator. Specifics can be seen in the section below.
Turbines are the main product used in generating wind energy. The towers are made of mostly steel while the blades of the turbine are constructed of glass-fiber polyester or wood-epoxy. Wind turbines used to create energy consist of rotor blades, which rotate, therefore turning a low-speed shaft. This shaft is connected to a gearbox and generator. The generator is a key product in the turbine because it produces electrical energy from mechanical energy. The anemometer collects wind speeds, which either turns the turbine on or off. Turbines are usually turned on between wind speeds of 9 and 15 miles per hour (mph). Wind turbines are usually shut off at approximately 65 mph due to possible overheating (USDOE). The yaw drive is implemented in upwind turbines to keep the turbine facing the proper wind direction. As for downwind turbine direction, that is controlled by the wind itself.
There are two main types of turbines, the horizontal axis wind turbine also called HAWTs and the veritical axis wind turbine also called VAWTs. Horizontal turbines have a much higher efficiancy rate when the two are compared.
Technological Advances in turbines have been very significant in the past 25 years. New Airfoil designs on horizontal wind turbines, such as the Zond Z-750. In the past 20 years has new air foil designs have increased electrical efficiancy by 20 to 30 percent(USDOE, 2002). Structural testing improvments have also shown to combat problems before they happen. Fatigue testing, strength static testing and photoelastic stress analysis are just some of the tests horizontal turbines must go through to reach international standards set by the International Electrotechnical Commision. The NREL has also developed testing elvaluations to comply with the international standard. Power electronics advances have also made the Zond Z-750 more lightweight which has also increased electrical generation efficiancy.
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Figure 3 to the left shows the potential for productive wind energy in the United States. Figure 3 is set up in terms of wind power classes 1 through 7. Sections that are in the category 4 or greater are available for advanced wind turbine technology at this current time. Sections 1-3 are not viable at this time for wind energy production. This means that areas colored in green, yellow, orange or red are suitable for wind energy production. The energy that can potentially be generated from geographical areas in classes 4-7 is extraordinary. The amount of electricity that can be generated is dependent upon spacing between turbines, efficiency of the machines, turbine hub height, and estimated energy loss(NWTC). |
Figure 3. U.S. Annual Wind Power Resource (NWTC, 2002)
The wind in the United States could produce more than 4.4 trillion kWh of electricity each year--more than one and one-half times the 2.7 trillion kWh of electricity consumed in the United States in 1990 (NWTC)." Wind energy production capacity in America has doubled in the last three years due such factors as federal tax incentive programs. To provide America with 20% of its annual electricity from wind power, only 0.6% of land would have to be used in the lower 48 states. Furthermore, only 5% of that land would be occupied with turbines(NWTC). The geographic areas of resource in the United States are widespread. The east coast from Maine south to New Jersey has class 4 winds. The Great Lakes show class 5 winds. Great wind energy potential is also shown along the Great Plains alone with western Texas north to Montana. The southeastern region of the United States lacks the wind speeds needed for efficient wind energy production. Energy companies like PacificCorp are taking advantage of the wind energy potential in the western region of the United States. Currently, PacificCorp operates two wind energy facilities, The Wyoming Wind Energy Project and The Rock River facility, also located in Wyoming. The Wyoming Wind Power facility is housed on 2,156 acres, roughly 2,134 of these acres are still available for such activities as grazing or farming. On a good day at this facility, enough electricity is generated to power 20,000 homes (PAC, 2002).
Wind speeds generated in the northeast states of Maine, New Hampshire, Vermont, Masssachusetts and Connecticut average class 3 or higher. The higher peaks in this region such as Whiteface Mountain, Vermont's Green Mountains, and New Hampshire's White Mountains recieve wind speeds in classes 6 and 7. These exposed, open faced ridges recieve optimum conditions for wind power generation. The lower hilltops in the northeast recieve wind speeds of classes 3 or 4, which can be productive if used by a residential customer. The exposed coastal ridges of the northeast also show potential for wind power generation. The northeast coast of Maine down to New Jersey recieves class 4 winds or higher. "However, high wind resource at relatively low elevations in mountainous regions can occur where the air flow is channeled through constrictions or corridors that enhance the wind speeds. These wind corridors vary in width from just a few kilometers to over 50 km (31 mi) (NREL, 2002)." Table 1 below shows the installed wind capacity compared to the overall potential of the northeast to generate wind energy.
Recently, Dennis Elliot and Marc Schwartz of the National Renewable Energy Laboratory in conjunction with a consulting meteorologist Ron Neirenberg, NREL conducted a wind resource mapping of the state of Vermont. This study was done using a Geographical Information System (GIS) software in order to be a specific as possible. In order to receive the most accurate account of Vermont's wind potential, the state was divided geographically into two sections. Lake Champlain valley extending north and south made up the western portion of the state. The Green Mountain chain including the Connecticut River Valley form the eastern portion of the state. The potential of Vermont's wind energy lies in the higher elevations which receive constant free-air winds mainly from the northwest. Results from the mapping show increasing free-air winds southwest to northeast in the state. "The free-air wind density power density at the ridge and mountain peak elevations in Vermont was established between 1000 and 1200 W/m2 (Elliot, 2002)." Near surface, bimodal winds occur in the Champlain Valley due to channeling between the Adirondacks and the Green Mountains. This results in typically lower wind speeds when compared to the higher ridges (Elliot, 2002).
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Figure 4, Wind Map of Vermont( VERA, 2002)
The state of Vermont has great potential for producing wind energy. Its mountainous terrain with high elevation open faced ridges records favorable wind speeds. Vermont’s total state land area is 24,017 km^2. This mostly rural landscape holds 511 km^2 of class 3+ or above windy land suitable for wind power production. The wind energy potential for Vermont is 5 billion kilowatt hours (kWh) per year (Elliot, 2002).The state of Vermont has currently one major windfarm in operation, and one in production at this time. The facility in operation is known as the Searsburg wind power facility. This facility is operated by Green Mountain Power (GMP) and was supported by the federal government through the Utility Wind Turbine Verification Program. By using an emission free energy source, the Searsburg wind power facility reduces air emissions by 22 million pounds per year (GMP, 2002). The second wind farm under construction is the little equinox, which will be located in Manchester, Vermont. This windfarm will generate 12 to 24 million kilowatt-hours per year. This will be enough power to for over 3 thousand homes per year. These turbines will stand on 200 foot tabular towers. "The equinox windfarm will prevent 70,000 pounds per day when compared to New England's existing fossil-fuel power plants (EEC, 2002)." The little equinox windfarm will be online hopefully by the fall of 2003.
Table 2. Monthly Mean Wind Speeds on Mount Mansfield, Vermont (VT,1999)
Note!
Wind speeds averaging 19-26 mph are class 7 wind speeds, the highest class available for wind power generation. Also, these speeds are being recorded on already developed mountains. The highest wind speeds recorded from these mountains are occuring in the winter season, when ski resorts in Vermont could use electricity the most.
Table 3. Diurnal Mean Wind Speeds at Mt. Mansfield (~4,000), Vermont (VT,1999)
Table 4. Burke Mountain Mean Monthly Wind Speeds (~3,000) (VT, 1999)
Table 5. Mean Wind Speeds at Grampa's Knob (~2,000 ft), Vermont (VT,1999)
When permitting wind power facilities in the northeast, such as Searsburg and Little Equinox, states’ insist upon three common elements that must be looked at. Firstly, a state-level regulatory process must take place, followed by a local process that almost always consists of local hearings. Environmental impact statements also must be filed concerning avian and other wildlife. When permitting windfarms in Vermont, the state level process requires a Certificate of Public Good pursuant to Section 248 of Chapter 30 of Vermont Statutes. Under this section, state agencies such as the Agency of Natural Resources, and local agencies such as planning commissions, public hearings, and legislative bodies must send notification of approval of such a facility or windfarm. Letters of approval would state that such a windfarm would not have opposing impacts on aesthetics or the natural environment.
Recently I wrote a letter to Congressman Bernie Sanders and Senator Patrick Leahy of Vermont regarding what efforts could be taken to bring wind energy to Vermont and the United States.
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1 Church St. 2nd Floor Burlington, VT 05401 |
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(802) 863-2525 1-800-642-3193 for Vermonters |
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American Wind Energy Association (AWEA)
Canadian Wind Energy Association
Elliot, Dennis Schwartz, Marc Nierenberg, Ron 2000.Wind Resource Mapping of the state of Vermont Retrieved on 5 March 2002 from http://www.state.vt.us/psd/ee/wind/WINDSTUDYREPORT.PDF
Endless Energy Corporation, 2002. Wind Turbine Energy Retrieved on May 2, 2002 from http://www.endlessenergy.com/equinox.html
Energy and Environmental Ventures LLC, 2002. Wind Energy in the Northeastern U.S. Retrieved on May 2, 2002 from
http://www.ctcleanenergy.com/resources/Wind%20Energy%20in%20the%20Northeastern%20US.pdf
National Renewable Energy Laboratory, 2002. Introduction to Wind Energy Retrieved on 20 March 2002 from http://nreldev.nrel.gov/clean_energy/wind.html
National Renewable Energy Laboratory, 2002. Wind Energy Resource Atlas of the United States Retrieved on May 2, 2002 from
http://rredc.nrel.gov/wind/pubs/atlas/chp2.html
National Wind Technology Center, 2002. U.S. Annual Wind Power Resource Retrieved on 25 March 2002 from http://www.nrel.gov/wind/usmaps.html
U.S. Department of Energy, 2002. Look at Wind Turbine Close up Retrieved on 11 February 2002 from http://www.eren.doe.gov/wind/feature.html
Vermont Environmental Research Associates, 2002. Autumn at Searsburg Wind Power Facility Retrieved on 12 March 2002 from
http://www.northeastwind.com/searsburg%20project.htm
Green Mountain Power, 2002. Wind for the planet Retrieved on May 2, 2002 from
http://www.gmpvt.com/enviro/searsburg.pdf
Vermont Environmental Research Associates, 2002. Wind map of Vermont Retrieved on May 2, 2002 from
http://www.northeastwind.com/northeastWP.htm
Renewable and Appropriate Energy Laboratories, 2002. Searsburg Wind Energy Facility Retrieved on May 2, 2002 from
http://ist-socrates.berkeley.edu/~rael/projects.html
CNN, 2002. Wind Turbine Configurations Retrieved on May 3, 2002 from http://www.cnn.com/2000/NATURE/06/14/wind.power/
State of Vermont, 2002. Mean Wind Speed on Mt. Mansfield Retrieved on the May 3, 2002 from the World WideWeb:
State of Vermont, 2002. Diurnal Mean Wind Speeds on Mt. Mansfield. Retrieved on May 3, 2002 from World Wide Web:
