Wind can be pretty complicated. But it doesn’t have to be. At One Energy, we make wind simple. Review the following pages covering Wind Terminology, Turbine Diagrams, Wind Maps, and Additional Resources and you’ll be on your way to becoming a wind expert.
- Distribution system: A power-line system that comprises the parts of an electric power system between the sub-transmission system and the consumers’ service switches. Typically these are the power lines installed on wooden poles that actually connect to your facility.
- Independent System Operator (ISO): An organization formed at the direction or recommendation of the Federal Energy Regulatory Commission (FERC). In the areas where an ISO is established, it coordinates, controls, and monitors the operation of the electric power system.
- Megawatt (MW): A unit of power equivalent to 1,000,000 watts.
- Megawatt hour (MWh): A megawatt hour (MWh) is equal to 1,000 kilowatt hours (kWh). It is equal to 1,000 kilowatts of electricity used for one hour.
- Modified Accelerated Cost Recovery System (MACRS): The current method of accelerated asset depreciation allowed for wind turbines by the United States income tax code.
- Nameplate capacity: The amount of power a wind turbine can produce at its rated wind speed. The definition of rated wind speed can be found below.
- Net metering: A series of state laws that state, for a given customer with a given generator (usually a clean energy generator), that the utility company can only bill based on the NET electricity consumed at the end of the billing period. This means it does not matter when you use the energy or when you produce it, because you are only billed on the net difference. In some cases, utilities are required to pay for net excess generation. Laws vary widely throughout the country.
- On-site generation wind energy: The use of a wind turbine to directly offset a facility’s electricity consumption under net metering rules.
- Renewable Energy Agreement (REA): A contract between two parties: one who generates electricity for the purpose of sale (the seller), and one who purchases the electricity (the buyer).
- Rated wind speed: The wind speed at which the turbine produces its nameplate-rated power.
- Renewable Energy Credit (REC): A certificate that is proof that one megawatt hour (MWh) of electricity was generated from a renewable energy resource. Once the electricity provider has fed the electricity into the grid, the REC they received can then be sold on the open market as a commodity. RECs provide an additional income stream to the energy provider, thus making it a bit more attractive to produce “green” energy.
- Transmission: The electric grid that connects generators to distribution substations.
- Turbine: A device for converting the flow of a fluid (air, steam, water, or hot gases) into mechanical motion that can be used to produce electricity.
- Nacelle: The cover that houses the generating components of a wind turbine, including the generator, gearbox, low and high speed shafts, controller, and brake assembly.
- Transformer: The transformer is a piece of electrical equipment used to step up or step down voltage. Most turbines have a dedicated transformer to step up their voltage to the grid voltage.
- Generator: Turbines usually use off-the-shelf induction generators that produce 60-cycle alternating current (AC) electricity.
- Gear box: Gears connect the low-speed shaft of the rotor to the high-speed shaft and increase the rotational speeds from about 30 to 60 revolutions per minute (rpm) to about 1200 to 1500 rpm, which is the rotational speed required by most generators to produce electricity. The gear box is a heavy and expensive part of the wind turbine. Some turbines now utilize “direct-drive” generators that operate at lower rotational speeds, therefore eliminating the need for gear boxes.
- Hub: A cast structure to which the blades are attached, creating the rotor (hub + 3 blades = rotor).
- Tower: Towers are made from tubular steel. Because wind speed increases with height, taller towers enable turbines to capture more energy and generate more electricity.
- Rotor: The blades and the hub together are called the rotor.
Wind Turbines and the Electric Grid
The diagram below illustrates how wind turbines connect to the electric grid.
A utility-scale wind farm, a nuclear power plant, and a coal-fired power plant are connected to the interstate electric grid, which is a network of high-voltage (50,000-700,000 volts) power lines. Power is sent to the distribution grid via regional substations, where the voltage is stepped down.
Large industrial consumers receive their power directly from the distribution grid at 4,000-35,000 volts. For residential consumers, a pole-mounted or pad-mounted transformer steps the power down again to 240 volts. The local electric utility company measures (and bills for) the power consumed by each customer with an electric meter (“M”).
On-site wind generation is different. One Energy installs one or more of the same utility-scale turbines used at wind farms, but right on the industrial consumer’s premises. Power is generated and used “behind the meter” at the consumers’ facility, directly offsetting power that would otherwise have been purchased at retail rates from the distribution grid. Any excess power generated is sent to the distribution grid.
Environmental Benefits of Wind Energy
The installation of just three 1.5 MW wind turbines has a significant positive environmental impact. A project of this scope could provide 13,797,000 kWh of electricity annually, and would avoid annual emissions equivalent to*:
- 9,514 metric tons of carbon dioxide
- CO2 emissions from using 1,066,569 gallons of gasoline
- Greenhouse gas emissions from 1,865 vehicles
- CO2 emissions from consuming 22,125 barrels of oil
- The carbon sequestered by 2,029 acres of pine or fir forests
- CO2 emissions from burning 4,708.1 metric tons of coal
- Greenhouse gas emissions from sending 3,315 tons of waste into a landfill
- The installation of just three 1.5 MW wind turbines would have the same positive environmental impact as planting 210,000 trees