What is the current hydropower capacity for the U.S. and what technologies are currently in place?

Facilities in the United States can generate enough power to supply 28 million households with electricity, the equivalent of nearly 500 million barrels of oil. The Department of Energy (DOE) estimates that the total U.S. hydropower capacity—including pumped storage facilities—is about 95,000 megawatts.[1] An estimated 7% of U.S. electricity is generated by hydropower.[2]

Hydropower facilities use captured 'water fuel,' to create electricity. Powered by the kinetic energy of flowing water, these facilities use turbines and generators to convert the kinetic energy into electricity. The electricity generated in the facilities is then delivered into the electrical grid to be used in homes, businesses and by industry.[3]

Where is hydropower generated?

The three primary types of hydropower facilities (or plants), where hydropower is generated, include impoundment, diversion and pumped storage. These facilities range in size from small systems for a home or village to large projects producing electricity for utilities. Some such facilities utilize dams, while others do not. In the U.S. there are an estimated 80,000 dams of which only 2,400 produce power.[4]

What key components make up a hydropower facility?

The following table provides definitions for the various components that comprise a hydropower facility/plant or turbine.[5]

• Alternating current (AC): Electric current that reverses direction many times per second.
• Ancillary services: Operations provided by hydroelectric plants that ensure stable electricity delivery and optimize transmission system efficiency.
• Cavitation: Noise or vibration causing damage to the turbine blades as a results of bubbles that form in the water as it goes through the turbine which causes a loss in capacity, head loss, efficiency loss, and the cavity or bubble collapses when they pass into higher regions of pressure.
• Direct current (DC): Electric current, which flows in one direction.
• Draft tube: A water conduit, which can be straight or curved depending upon the turbine installation, that maintains a column of water from the turbine outlet and the downstream water level.
• Efficiency: A percentage obtained by dividing the actual power or energy by the theoretical power or energy. It represents how well the hydropower plant converts the energy of the water into electrical energy.
• Head: Vertical change in elevation, expressed in either feet or meters, between the head water level and the tailwater level.
• Flow: Volume of water, expressed as cubic feet or cubic meters per second, passing a point in a given amount of time.
• Headwater: The water level above the powerhouse.
• Low Head: Head of 66 feet or less.
• Penstock: A closed conduit or pipe for conducting water to the powerhouse.
• Runner: The rotating part of the turbine that converts the energy of falling water into mechanical energy.
• Scroll case: A spiral-shaped steel intake guiding the flow into the wicket gates located just prior to the turbine.
• Small hydro: Projects that produce 30 MW or less.
• Tailrace: The channel that carries water away from a dam.
• Tailwater: The water downstream of the powerhouse.
• Ultra low head: Head of 10 feet or less.
• Wicket gates: Adjustable elements that control the flow of water to the turbine passage.

How is hydropower transmitted?

Once electricity is produced, it must be delivered to where it needs to go, including homes, schools, offices, factories, etc. In order to get the power from the source dams to distance users, vast networks of transmission lines and facilities are used to bring electricity to us in a form we can use. Power plant electricity comes first through a transformer, which raises the voltage to force-pressure the power long distances through power lines. Transformers on poles further reduce the electric power, so that it is at the right voltage for appliances within our homes. When electricity comes into our homes, we purchase it by the kilowatt-hour, a meter measures how much is used.

In additional to hydroelectric power plants, other power plant sources include gas-turbines, geothermal, wind powered systems and more. These powerplants use the same general system of transmission lines. A power grid allows electricity to be interchanged among several utility systems to meet varying demands. Essentially, the electricity running your computer could be from a hydroelectric power plant, a wind generator, a nuclear facility, or a coal, gas or oil fired power plant, or a combination of these.[7]

Research by Theresa Pipher