Hydropower is a renewable energy source, meaning it can be replenished naturally and relatively quickly. Water is drawn from rivers or reservoirs to spin turbines that generate electricity, before being returned back into the water cycle.
While hydropower doesn’t produce greenhouse gas emissions as fossil fuels do, the large-scale dams needed to capture the flowing water can impact the environment both upstream and downstream of the dam.
Renewable hydropower is derived from water flowing through a dam that turns turbines to produce electricity.
There Are Several Types Of Hydropower
1. Conventional dams
A dam on a river forms a reservoir behind it and water is released to spin a turbine connected to a generator, which produces electricity.
2. Pumped Storage
Water is pumped from a lower reservoir to a higher one when electricity is plentiful and inexpensive. The water is then released back down through turbines to generate electricity when demand is high.
3. Run-of-river
A dam diverts some of a river’s flow into a pipe, called a penstock. The water accelerates and spins a turbine connected to a generator.
4. Wave
A device captures the energy of ocean surface waves and converts it to electricity.
5. Tidal
A dam across a tidal estuary traps rising water during a flood tide. When the tide ebbs, gates are opened and the water flows back out, spinning turbines as it goes.
Sizes Of Hydroelectric Power Plants
Hydropower facilities range in size from large power plants that supply many consumers with electricity to small projects that provide power to just a few homes.
The U.S. Geological Survey (USGS) estimates that there are about 80,000 dams taller than 15 feet in the United States, but only 3% of them generate electricity.
Large Hydropower Plants
Large hydropower plants usually have a capacity of 1 megawatt (MW) or more. The Three Gorges Dam in China, for example, has a capacity of 22,500 MW—enough to power more than 11 million homes.
Small Hydropower Plants
Small hydropower plants have a capacity of less than 1 MW. Many small hydropower plants are located at existing dams or on canals.
Microhydro Systems
Microhydro systems usually generate up to 100 kilowatts (kW) of electricity. These systems use the natural flow of water and do not require a dam.
Pico Hydro Systems
Pico hydro systems generate up to 5 kW of electricity. These small-scale water power systems can provide power to a single home or a small village.
How Does Hydropower Work
Hydropower plants capture the energy of flowing water and use it to generate electricity.
All hydropower plants use turbines to convert the kinetic energy of moving water into mechanical energy.
The most common type of turbine used in hydropower plants is the Francis turbine. The Francis turbine has blades that spin on a shaft inside a chamber of water.
As the water flows through the turbine, the blades spin the shaft. The shaft is connected to a generator that produces electricity.
What Are The Benefits Of Hydropower?
Hydropower is a renewable energy source that generates electricity with little to no pollution.
Hydropower is a flexible power source, meaning it can ramp up or down quickly to meet changing electricity demand. This flexibility is important in light of the intermittency of other renewable energy sources, such as wind and solar.
Hydropower is a domestic energy source, which reduces our reliance on imported fuels.
How Much Of The United States’ Electricity Comes From Hydropower?
According to the U.S. Department of Energy’s Hydroelectric Power Generation report, hydropower generated about 6% of the electricity in the United States in 2019.
Types of Pumped Storage Plants:
Pumped-storage hydropower plants store water in a reservoir located at a higher elevation than the turbines.
During periods of low electricity demand, typically at night, the excess power generated by other power plants is used to pump water from a lower reservoir to the upper reservoir.
When there is high demand for electricity during the day, water is released from the upper reservoir back down to the lower one, passing through turbines that generate electricity on the way.
Pumped-storage hydropower is like a battery for the panel, providing stored energy during periods of peak demand.
Reversible Turbine Hydro Power Plants
A reversible turbine hydropower plant is a type of hydropower plant that uses a reversible turbine. The turbine can be used to generate electricity or to pump water from a lower elevation to a higher elevation.
Reversible turbine hydropower plants are typically used for pumped-storage applications, although they can also be used for other purposes such as peak load shaving, baseload support, and grid stability.
The two main types of reversible turbine hydropower plants are crossflow turbines and Kaplan turbines.
Crossflow Turbines
Crossflow turbines are a type of reversible turbine hydropower plant that uses a crossflow turbine. The crossflow turbine is a modification of the Francis turbine, which is a type of reaction turbine.
The crossflow turbine was invented by James Francis in 1849. The crossflow turbine is more efficient than the Francis turbine and can be used for both generating electricity and pumping water.
Kaplan Turbines
Kaplan turbines are a type of reversible turbine hydropower plant that uses a Kaplan turbine. The Kaplan turbine is a modification of the propeller turbine, which is a type of reaction turbine.
The Kaplan turbine was invented by Viktor Kaplan in 1913. The Kaplan turbine is more efficient than the propeller turbine and can be used for both generating electricity and pumping water.
Underground Hydropower Plants
An underground power plant is a type of hydropower plant that uses water flowing through tunnels to spin turbines that generate electricity.
Underground power plants are typically located in mountains, where they can take advantage of steep elevation changes to generate electricity.
The Advantages Of Underground Hydropower Plants Are
- They are less visible than surface power plants and can be located near population centers without adversely affecting the landscape.
- They can take advantage of steep elevation changes to generate electricity, which is not possible with surface power plants.
- They are less likely to be affected by drought than surface power plants.
The Disadvantages Of Underground Hydropower Plants Are
- They are more expensive to build than surface power plants.
- They can be difficult to maintain and repair.