Hydro Electric Power

• California's and the nation's electricity. In 2004, about 16.5 percent of the total electricity in California is from hydro -- 14.9 percent from large hydroelectric plants, and about 1.6 percent is from small hydro facilities, which are 30 megawatts or smaller in size. Nationally, according to the U.S. Department of Energy, hydro accounts for about 10 percent of the country's total electricity production - about 95,000 megawatts.

• Hydroelectric power, a renewable resource, is generated when hydraulic turbines are turned by the force of moving water as it flows through a turbine. The water typically flows from a higher to a lower elevation. these turbines are connected to electrical generators, which produce the power. The efficiency of such systems can be close to 90 percent.

How Hydro Power Works!

• Hydro means "water". So, hydropwer is "water power." Potential energy (or the 'stored" energy in a reservoir) becomes kenetic (or moving energy). This is changed to mechanical energy in a power plant, which is then turned into electrical energy.

• Water is stored behind a dam in a reservoir. In the dam is a water intake. This is a narrow opening to a tunnel called a penstock.

• Water pressure (from the weight of the water and gravity) forces the water through the penstock and onto the blades of a turbine.A turbine is similar to the blades of a child's pinweel. But instead of breath making the pinwheel turn, the moving water pushes the blades and turns the turbine.

• The turbine spins because of the force of the water.The turbine is connected to an electrical generator inside the powerhouse.The generator produces electricity that travels over long-distance power lines to homes and businesses.The entire process is called "hydroelectricity".

Types of Hydro Facilities

• The water used by hydro plants can be flowing in naturals streams or rivers,or contained in man-made facilities such as reservoirs, pipelines,or canals. There are two main categories of hydroelectric power generation: conventional methods, which produce electricity via water flow in one direction; and pumped storage methods, which are both producers and comsumers of electricity. In a pumped storage facility, water from a higher elevatin reservoirs flows to a lower elevation reservoirs during peak demand periods -- such as during hot afternoons. During off-peaks periods, the water is recycled and pumped from the lower reservoir back to the higher reservoir to be used again during the next peak period.

• Two types of conventional hydro plants are dams and run-of-the-river. Dams raise the water level of a stream or to an elevation needed to create water pressure or "head." Dams can be constructed of earth, concreate, steel or a combination of such materials. Dams may create secondary benefits such as flood control, recreation opportunities and water storage.

• Run-of-rive, or water diversion, facilities typically divert water from its natural channel to run through a turbine. The water it uses is usually returned to the channel downstream of the turbine.

• small or low-impact hydro may be a misnomer. Size of energy-producing facilities doesn't necessarily mean smaller envinronmental impacts. Hydro plants along small rivers or streams may be harmful to fish and other aquatic species. of the roughly 2,000 private hydro facilities in the United States, about 89 percent can be categorized as small hydro.

[edit] Hydroelectric power: How it works

So just how do we get electricity from water? Actually, hydroelectric and coal-fired power plants produce electricity in a similar way. In both cases a power source is used to turn a propeller-like piece called a turbine, which then turns a metal shaft in an electric generator, which is the motor that produces electricity. A coal-fired power plant uses steam to turn the turbine blades; whereas a hydroelectric plant uses falling water to turn the turbine.

The theory is to build a dam on a large river that has a large drop in elevation (there are not many hydroelectric plants in Kansas or Florida). The dam stores lots of water behind it in the reservoir. Near the bottom of the dam wall there is the water intake. Gravity causes it to fall through the penstock inside the dam. At the end of the penstock there is a turbine propeller, which is turned by the moving water. The shaft from the turbine goes up into the generator, which produces the power. Power lines are connected to the generator that carry electricity to your home and mine. The water continues past the propeller through the tailrace into the river past the dam. By the way, it is not a good idea to be playing in the water right below a dam when water is released!

"A hydraulic turbine converts the energy of flowing water into mechanical energy. A hydroelectric generator converts this mechanical energy into electricity. The operation of a generator is based on the principles discovered by Faraday. He found that when a magnet is moved past a conductor, it causes electricity to flow. In a large generator, electromagnets are made by circulating direct current through loops of wire wound around stacks of magnetic steel laminations. These are called field poles, and are mounted on the perimeter of the rotor. The rotor is attached to the turbine shaft, and rotates at a fixed speed. When the rotor turns, it causes the field poles (the electromagnets) to move past the conductors mounted in the stator. This, in turn, causes electricity to flow and a voltage to develop at the generator output terminals."

[edit] Pumped storage: Reusing water for peak electricity demand

Demand for electricity is not "flat" and constant. Demand goes up and down during the day, and overnight there is less need for electricity in homes, businesses, and other facilities. For example, here in Atlanta, Georgia at 5:00 PM on a hot August weekend day, you can bet there is a huge demand for electricity to run millions of air conditioners! But, 12 hours later at 5:00 AM .... not so much. Hydroelectric plants are more efficient at providing for peak power demands during short periods than are fossil-fuel and nuclear power plants, and one way of doing that is by using "pumped storage", which reuses the same water more than once.

Pumped storage is a method of keeping water in reserve for peak period power demands by pumping water that has already flowed through the turbines back up a storage pool above the powerplant at a time when customer demand for energy is low, such as during the middle of the night. The water is then allowed to flow back through the turbine-generators at times when demand is high and a heavy load is placed on the system.

The reservoir acts much like a battery, storing power in the form of water when demands are low and producing maximum power during daily and seasonal peak periods. An advantage of pumped storage is that hydroelectric generating units are able to start up quickly and make rapid adjustments in output. They operate efficiently when used for one hour or several hours. Because pumped storage reservoirs are relatively small, construction costs are generally low compared with conventional hydropower facilities.