What is Hydroelectric Power?

Flowing water creates energy that can be captured and turned into electricity. This is called hydroelectric power. The most common type of hydroelectric power plant uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. However, hydroelectric power does not necessarily require a large dam. Some hydroelectric power power plants just use a small canal to channel the river water through a turbine. Another type of plant, called a pumped storage plant, can even store power. The power is sent from a power grid into the electric generators. The generators then spin the turbines backward, which causes the turbines to pump water from a river or lower reservoir to an upper reservoir, where the power is then stored. To use the power, the water is released from the upper reservoir back down into the river or lower reservoir. This spins the turbines forward, activating the generators to produce electricity.

The Importance of Hydroelectric Power

Hydroelectric power is fueled by water, so it is a clean fuel source, meaning it won’t pollute the air like power plants that burn fossil fuels, such as coal or natural gas. Hydroelectricity is a domestic source of energy, which allows any state or nation to produce their own energy without being reliant on international fuel sources. The energy generated through hydroelectric power relies on the water cycle, which is driven by the sun, making it a renewable power source and a more reliable and affordable source than fossil fuels that are rapidly being depleted. Impoundment hydroelectric power creates reservoirs that offer a variety of recreational opportunities, notably fishing, swimming, and boating. Most water power installations are required to provide some public access to the reservoir to allow the public to take advantage of these opportunities. Some hydroelectric power facilities can quickly go from zero power to maximum output. As a result, hydropower plants can generate power to the grid immediately, which can provide essential back-up power during major electricity outages or disruptions. In addition to a sustainable fuel source, hydroelectric power efforts produce a number of secondary benefits such as flood control, irrigation, and backup water supplies.


How Does Hydroelectric Power Work?

Hydroelectric power plants capture the energy of falling water to generate electricity. A turbine converts the kinetic energy of falling water into mechanical energy. Then a generator converts the mechanical energy from the turbine into electrical energy. Hydroelectric power plants range in size from micro-hydros that power only a few homes to giant dams, like Hoover Dam, which provide electricity for millions of people.

Most conventional hydroelectric plants include four major components:

Dam: This raises the water level of the river to create falling water and controls the flow of water. It also forms a reservoir, which is, in effect, stored energy.

Turbine: The force of falling water pushing against the turbine’s blades causes the turbine to spin. A water turbine is much like a windmill, except the energy is provided by falling water instead of wind. The turbine converts the kinetic energy of falling water into mechanical energy.

Generator: This is connected to the turbine by either shafts or gears so that when the turbine spins it causes the generator to spin also, which then converts the mechanical energy from the turbine into electrical energy. Generators in hydroelectric power plants work just like the generators in other types of power plants.

Transmission lines: These lines conduct electricity from the hydroelectric power plants to homes and businesses.


How Much Hydroelectric Power Can Be Produced?

The U.S. has 78 GW of hydroelectric capacity installed. In a year, these plants produce 272 TWh of energy. The United States produces, annually, 0.031 TW, or 31 GW, of average power. This implies a 40% capacity factor. So what fraction of the United States’ energy currently comes from hydroelectricity? Of the delivered electricity, it’s 7.3%; so on average, 272 TWh of annually delivered electricity in the U.S. corresponds to 0.9% of the primary energy use, or 2.3% of primary energy associated with electricity. Essentially, in the United States, actual hydroelectric power production does not meet the potential for overall hydroelectric power production. The United States is not the only country that produces hydroelectric power. At the end of 2011, over 160 countries had hydroelectric power resources available, with a total capacity of 936 GW of potential energy across 11,000 hydroelectric power stations. The leading generating countries were China, Canada, Brazil, and the United States respectively, although it is worth noting that Norway and India both have significant hydroelectric power generation, particularly relative to their size and total electricity supply. In all of these cases; however, much the same as it is in the United States, production does not match potential. Were it to do so, hydroelectric power would be a serious competitor with fossil fuels.