Why is hydropower used

Understanding the water cycle is important to understanding hydropower. The water cycle has three steps: Solar energy heats water on the surface of rivers, lakes, and oceans, which causes the water to evaporate.

Water vapor condenses into clouds and falls as precipitation—rain and snow. Precipitation collects in streams and rivers, which empty into oceans and lakes, where it evaporates and begins the cycle again.

The amount of precipitation that drains into rivers and streams in a geographic area determines the amount of water available for producing hydropower. Seasonal variations in precipitation and long-term changes in precipitation patterns, such as droughts, can have large effects on the availability of hydropower production.

Because the source of hydroelectric power is water, hydroelectric power plants are usually located on or near a water source. The volume of the water flow and the change in elevation—or fall, and often referred to as head —from one point to another determine the amount of available energy in moving water. In general, the greater the water flow and the higher the head, the more electricity a hydropower plant can produce. At hydropower plants water flows through a pipe, or penstock , then pushes against and turns blades in a turbine to spin a generator to produce electricity.

Conventional hydroelectric facilities include Run-of-the-river systems , where the force of the river's current applies pressure on a turbine. The facilities may have a weir in the water course to divert water flow to hydro turbines. Storage systems , where water accumulates in reservoirs created by dams on streams and rivers and is released through hydro turbines as needed to generate electricity.

Most U. Pumped-storage hydropower facilities are a type of hydroelectric storage system where water is pumped from a water source up to a storage reservoir at a higher elevation and is released from the upper reservoir to power hydro turbines located below the upper reservoir.

The electricity for pumping may be supplied by hydro turbines or by other types of power plants including fossil fuel or nuclear power plants. Pumped-storage hydroelectric systems generally use more electricity to pump water to the upper water storage reservoirs than they produce with the stored water.

Therefore, pumped-storage facilities have net negative electricity generation balances. The U. Energy Information Administration publishes electricity generation from pumped storage hydroelectric power plants as negative generation. Click to enlarge. Hydropower is one of the oldest sources of energy for producing mechanical and electrical energy and up until , it was the largest source of total annual U.

Thousands of years ago, people used hydropower to turn paddle wheels on rivers to grind grain. Before steam power and electricity were available in the United States, grain and lumber mills were powered directly with hydropower. The first industrial use of hydropower to generate electricity in the United States was in to power 16 brush-arc lamps at the Wolverine Chair Factory in Grand Rapids, Michigan.

At the plant level, water flows through a pipe—also known as a penstock—and then spins the blades in a turbine, which, in turn, spins a generator that ultimately produces electricity.

Most conventional hydroelectric facilities operate this way, including run-of-the-river systems and pumped storage systems. Learn More. Hydropower News. Speakers will share highlights on each WPTO topic and sub-topic. STEM disciplines, or the fields of Science, Technology, Engineering, and Mathematics, are critical to understanding our world and developing solutions to complex challenges. Operating a hydroelectric power plant may also change the water temperature and the river's flow.

These changes may harm native plants and animals in the river and on land. Reservoirs may cover people's homes, important natural areas, agricultural land, and archaeological sites. So, building dams can require relocating people. Methane, a strong greenhouse gas, may also form in some reservoirs and be emitted to the atmosphere.

Gosh, hydroelectric power sounds great — so why don't we use it to produce all our power? Mainly because you need lots of water and a lot of land where you can build a dam and reservoir , which all takes a LOT of money, time, and construction. In fact, most of the good spots to locate hydro plants have already been taken. In the early part of the century hydroelectric plants supplied a bit less than one-half of the nation's power, but the number is down to about 10 percent today.

The trend for the future will probably be to build small-scale hydro plants that can generate electricity for a single community. As this chart shows, the construction of surface reservoirs has slowed considerably in recent years.

In the middle of the 20th Century, when urbanization was occurring at a rapid rate, many reservoirs were constructed to serve peoples' rising demand for water and power. Since about , the rate of reservoir construction has slowed considerably. Hydroelectric energy is produced by the force of falling water.

The capacity to produce this energy is dependent on both the available flow and the height from which it falls. Building up behind a high dam, water accumulates potential energy. This is transformed into mechanical energy when the water rushes down the sluice and strikes the rotary blades of turbine. The turbine's rotation spins electromagnets which generate current in stationary coils of wire. Finally, the current is put through a transformer where the voltage is increased for long distance transmission over power lines.

Falling water produces hydroelectric power. 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. This chart shows hydroelectric power generation in for the leading hydroelectric-generating countries in the world. China has developed large hydroelectric facilities in the last decade and now lead the world in hydroelectricity usage.

But, from north to south and from east to west, countries all over the world make use of hydroelectricity—the main ingredients are a large river and a drop in elevation along with money, of course.

Credit: Energy Information Administration.