Alternative Fuel Sources Minerals, coal, oil and gas are all examples of nonrenewable resources and most of these pollute the environment when used. Most alternatives to fossil fuels use renewable resources (resources that can be replenished rapidly by nature), which are usually pollute the environment less. There are many forms of alternative fuels that are being utilized today: classic solar, nuclear, wind, hydro and geothermal power to the newly invented Tidal power generators and fuel cells. Solar Energy: Photovoltaic cells are used to convert radiative energy from the sun into electrical energy (energy is transfered from the sun to the earth by photons instead of atoms). Light energy is transfered to electrical energy by the process called the photoelectric effect. Solar thermal technology is also available and uses heat from the sun to warm the water in your house. Solar thermal electric plants use solar energy to convert water into steam which powers turbines and produces electricity. Nuclear Energy: Energy is released during a nuclear reaction (fission or fusion). All nuclear power plants work on the fission principle where an atom’s nucleus is split into smaller nuclei and energy is released. While nuclear engery production produces little local environmental impact (unlike un-scrubbed coal plants), the major problem with nuclear energy is the disposal of nuclear waste such as spent uranium. Another concern is for the safety of these plants in case of a meltdown but there are several precautions taken when constructing these plants, like a lead containment shield and several layers of concrete around the core of the plant. Nuclear engery production produces little local environmental impact, with the major concerns being waste disposal and Wind Energy: As the wind blows, the blades on a wind turbine drive a generator, producing electricity. Wind turbines are set up in some of the windiest places on earth since the faster the wind blows, the faster the turbine spins and more electricity is produced. Unlike solar power that can only run during sunny hours, wind turbines can run constantly all day. Look at the Wind Turbine Close Up Wind Turbine Glossary Anemometer: Measures the wind speed and transmits wind speed data to the controller. Blades: Most turbines have either two or three blades. Wind blowing over the blades causes the blades to "lift" and rotate. Brake: A disc brake which can be applied mechanically, electrically, or hydraulically to stop the rotor in emergencies. Controller: The controller starts up the machine at wind speeds of about 8 to 16 miles per hour (mph) and shuts off the machine at about 65 mph. Turbines cannot operate at wind speeds above about 65 mph because their generators could overheat. Gear box: Gears connect the low-speed shaft to the high-speed shaft and increase the rotational speeds from about 30 to 60 rotations per minute (rpm) to about 1200 to 1500 rpm, the rotational speed required by most generators to produce electricity. The gear box is a costly (and heavy) part of the wind turbine and engineers are exploring "direct-drive" generators that operate at lower rotational speeds and don't need gear boxes. Generator: Usually an off-the-shelf induction generator that produces 60-cycle AC electricity. High-speed shaft: Drives the generator. Low-speed shaft: The rotor turns the low-speed shaft at about 30 to 60 rotations per minute. Nacelle: The rotor attaches to the nacelle, which sits atop the tower and includes the gear box, low- and high-speed shafts, generator, controller, and brake. A cover protects the components inside the nacelle. Some nacelles are large enough for a technician to stand inside while working. Pitch: Blades are turned, or pitched, out of the wind to keep the rotor from turning in winds that are too high or too low to produce electricity. Rotor: The blades and the hub together are called the rotor. Tower: Towers are made from tubular steel (shown here) or steel lattice. Because wind speed increases with height, taller towers enable turbines to capture more energy and generate more electricity. Wind direction: This is an "upwind" turbine, so-called because it operates facing into the wind. Other turbines are designed to run "downwind", facing away from the wind. Wind vane: Measures wind direction and communicates with the yaw drive to orient the turbine properly with respect to the wind. Yaw drive: Upwind turbines face into the wind; the yaw drive is used to keep the rotor facing into the wind as the wind direction changes. Downwind turbines don't require a yaw drive, the wind blows the rotor downwind. Yaw motor: Powers the yaw drive. Courtesy of http://www.eere.energy.gov/wind/feature.html Hydro-Electric Energy: Flowing water is used to push turbines which generate electricity. Several steps can be taken to maximize the power provided by hydro-electric plants like storing water by using a dam to increase the height the water will fall and thus giving the water a higher potential energy, thus increasing the flow of water (speed) by diverting part of the waterway to other paths or using the natural drop of the waterway to power the Hydro-Electric plant. The flow to a lower level, causes electric generation; therefore, the higher mass flow rate (ammount of water per time period * speed), the more energy generation that can occur. Dam - Most hydropower plants rely on a dam that holds back water, creating a large reservoir. Often, this reservoir is used as a recreational lake, such as Lake Roosevelt at the Grand Coulee Dam in Washington State. Intake - Gates on the dam open and gravity pulls the water through the penstock, a pipeline that leads to the turbine. Water builds up pressure as it flows through this pipe. Turbine - The water strikes and turns the large blades of a turbine, which is attached to a generator above it by way of a shaft. The most common type of turbine for hydropower plants is the Francis Turbine, which looks like a big disc with curved blades. A turbine can weigh as much as 172 tons and turn at a rate of 90 revolutions per minute (rpm), according to the Foundation for Water & Energy Education (FWEE). Generators - As the turbine blades turn, so do a series of magnets inside the generator. Giant magnets rotate past copper coils, producing alternating current (AC) by moving electrons. (You'll learn more about how the generator works later.) Transformer - The transformer inside the powerhouse takes the AC and converts it to higher-voltage current. Power lines - Out of every power plant come four wires: the three phases of power being produced simultaneously plus a neutral or ground common to all three. (Read How Power Distribution Grids Work to learn more about power line transmission.) Outflow - Used water is carried through pipelines, called tailraces, and re-enters the river downstream. Courtesy of http://people.howstuffworks.com/hydropower-plant.htm

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