Hydropower Basics

Energy From Moving Water

Source: National Energy Education Development Project (Public Domain)

Source: Tennessee Valley Authority (Public Domain)

Hydropower Generates Electricity

Hydropower is the renewable energy source that produces the most electricity in the United States. It accounted for 6% of total U.S. electricity generation and 67% of generation from renewables in 2008.

Hydropower Relies on the Water Cycle

Understanding the water cycle is important to understanding hydropower. In the water cycle:

• Solar energy heats water on the surface, causing it to evaporate.
• This water vapor condenses into clouds and falls back onto the surface as precipitation (rain, snow, etc.).
• The water flows through rivers back into the oceans, where it can evaporate and begin the cycle over again.

Mechanical Energy Is Harnessed from Moving Water

The amount of available energy in moving water is determined by its flow or fall. Swiftly flowing water in a big river, like the Columbia River that forms the border between Oregon and Washington, carries a great deal of energy in its flow. Water descending rapidly from a very high point, like Niagara Falls in New York, also has lots of energy in its flow.

In either instance, the water flows through a pipe, or penstock, then pushes against and turns blades in a turbine to spin a generator to produce electricity. In a run-of-the-river system, the force of the current applies the needed pressure, while in a storage system, water is accumulated in reservoirs created by dams, then released as needed to generate electricity. Watch a video about hydropower on the Bonneville Power Administration website.

History of Hydropower

Hydropower is one of the oldest sources of energy. It was used thousands of years ago to turn a paddle wheel for purposes such as grinding grain.  Our Nation's first industrial use of hydropower to generate electricity occurred in 1880, when 16 brush-arc lamps were powered using a water turbine at the Wolverine Chair Factory in Grand Rapids, Michigan.

The first U.S. hydroelectric power plant opened on the Fox River near Appleton, Wisconsin, on September 30, 1882.

Because the source of hydroelectric power is water, hydroelectric power plants must be located on a water source. Therefore, it wasn't until the technology to transmit electricity over long distances was developed that hydropower became widely used.

For more information about hydropower, see Hoover Dam, a hydroelectric facility completed in 1936 on the Colorado River between Arizona and Nevada. this dam created Lake Mead, a 110-mile-long national recreational area that offers water sports and fishing in a desert setting.

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Where Hydropower is Generated

Data for this map

Most U.S. Hydropower Is in the West

Over half of U.S. hydroelectric capacity for electricity generation is concentrated in three States: Washington, California, and Oregon. Approximately 31% of the total U.S. hydropower is generated in Washington, the location of the Nation's largest hydroelectric facility — the Grand Coulee Dam.

Most hydropower is produced at large facilities built by the Federal Government, such as the Grand Coulee Dam. The West has most of the largest dams, but there are numerous smaller facilities operating around the country.

Most Dams Were Not Built for Power

Only a small percentage of all dams in the United States produce electricity. Most dams were constructed solely to provide irrigation and flood control.

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Hydropower & the Environment

Hydropower Generators Produce Clean Electricity, but Hydropower Does Have Environmental Impacts

Most dams in the United States were built mainly for flood control and supply of water for cities and irrigation. A small number of dams were built specifically for hydropower generation. While hydropower (hydro-electric) generators do not directly produce emissions of air pollutants, hydropower dams, reservoirs, and the operation of generators can have environmental impacts.

Fish Ladder at the Bonneville Dam on the Columbia River Separating Washington and Oregon

Source: Stock photography (copyrighted)

A dam to create a reservoir may obstruct migration of fish to their upstream spawning areas. A reservoir and operation of the dam can also change the natural water temperatures, chemistry, flow characteristics, and silt loads, all of which can lead to significant changes in the ecology (living organisms and the environment) and rocks and land forms of the river upstream and downstream. These changes may have negative impacts on native plants and animals in and next to the river, and in the deltas that form where rivers empty into the ocean. Reservoirs may cover important natural areas, agricultural land, and archeological sites, and cause the relocation of people.

Greenhouse gases, carbon dioxide and methane, may also form in reservoirs and be emitted to the atmosphere. The exact amount of greenhouse gases produced from hydropower plant reservoirs is uncertain.  The emissions from reservoirs in tropical and temperate regions, including the United States, may be equal to or greater than the greenhouse effect of the carbon dioxide emissions from an equivalent amount of electricity generated with fossil fuels.

Fish Ladders Help Salmon Reach Their Spawning Grounds

Hydro turbines kill and injure some of the fish that pass through the turbine. The U.S. Department of Energy has sponsored research and development of turbines that could reduce fish deaths to less than 2%, in comparison to fish kills of 5 to 10% for the best existing turbines.

In the Columbia River, along the border of Oregon and Washington, salmon must swim upstream to their spawning grounds to reproduce, but the series of dams along the river gets in their way. Different approaches to fixing this problem have been used, including the construction of "fish ladders" that help the salmon "step up" and around the dam to the spawning grounds upstream.

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Tidal Power

Tides are caused by the gravitational pull of the moon and sun, and the rotation of the Earth. Near shore, water levels can vary up to 40 feet due to tides.

Dam of the Tidal Power Plant on the Estuary of the Rance River, Bretagne, France

Source: Stock photography (copyrighted)

Tidal power is more predictable than wind energy and solar power. A large enough tidal range — 10 feet — is needed to produce tidal energy economically.

Tidal Barrages

A simple generation system for tidal plants involves a dam, known as a barrage, across an inlet. Sluice gates (gates commonly used to control water levels and flow rates) on the barrage allow the tidal basin to fill on the incoming high tides and to empty through the turbine system on the outgoing tide, also known as the ebb tide. There are two-way systems that generate electricity on both the incoming and outgoing tides.

A potential disadvantage of tidal power is the effect a tidal station can have on plants and animals in the estuaries. Tidal barrages can change the tidal level in the basin and increase turbidity (the amount of matter in suspension in the water). They can also affect navigation and recreation.

There are currently two commercial-sized barrages operating in the world. One is located in La Rance, France; the other is in Annapolis Royal, Nova Scotia, Canada. There is a third experimental 400 kW tidal barrage operating in Kislaya Guba, Russia.

Source: Adapted from National Energy Education Development Project (Public Domain)

The United States has no tidal plants and only a few sites where tidal energy could be produced economically. France, England, Canada, and Russia have much more potential to use this type of energy.

Tidal Fences

Tidal fences can also harness the energy of tides. A tidal fence has vertical axis turbines mounted in a fence. All the water that passes is forced through the turbines. Tidal fences can be used in areas such as channels between two landmasses. Tidal fences are cheaper to install than tidal barrages and have less impact on the environment than tidal barrages, although they can disrupt the movement of large marine animals.

A tidal fence is planned for the San Bernardino Strait in the Philippines.

Tidal Turbines

Tidal turbines are basically wind turbines in the water that can be located anywhere there is strong tidal flow. Because water is about 800 times denser than air, tidal turbines have to be much sturdier than wind turbines. Tidal turbines are heavier and more expensive to build but capture more energy.

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Wave Power

Waves Have Lots of Energy

The Pelamis Wave Power Device in Use in Portugal

Source: Wind & Hydropower Technologies Program, U.S. Department of Energy, Energy Efficiency and Renewable Energy (Public Domain)

Wave Energy Site

Source: Adapted from NEED.

CETO Underwater Wave Energy Device

Source: Tuscanit, Wikimedia Commons author (GNU Free Documentation License) (Public Domain)

Waves are caused by the wind blowing over the surface of the ocean. There is tremendous energy in the ocean waves. It's estimated that the total potential off the coast of the United States is 252 billion kilowatthours a year, about 7% of the United States' electricity consumption in 2008. The west coasts of the United States and Europe and the coasts of Japan and New Zealand are good sites for harnessing wave energy.

Different Ways To Channel the Power of Waves

One way to harness wave energy is to bend or focus the waves into a narrow channel, increasing their power and size. The waves can then be channeled into a catch basin or used directly to spin turbines.

Many more ways to capture wave energy are currently under development. Some of these devices being developed are placed underwater, anchored to the ocean floor, while others ride on top of the waves. The world's first commercial wave farm using one such technology opened in 2008 at the Aguçadora Wave Park in Portugal.

See all the technologies under development at the U.S. Department of Energy's Marine and Hydrokinetic Technology Database.

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Ocean Thermal

Ocean Thermal Energy Conversion System

OTEC Plant on the Kona Coast of Hawaii

Source: U.S. Department of Energy (Public Domain)

The energy from the sun heats the surface water of the ocean. In tropical regions, the surface water can be much warmer than the deep water. This temperature difference can be used to produce electricity. The Ocean Thermal Energy Conversion (OTEC) system must have a large temperature difference of at least 77°F to operate, limiting its use to tropical regions.

Hawaii has experimented with OTEC since the 1970s. There is no large-scale operation of OTEC today, mainly because there are many challenges. The OTEC systems are not very energy efficient. Pumping water is a major engineering challenge.

Electricity generated by the system must be transported to land. It will probably be 10 to 20 years before the technology is available to produce and transmit electricity economically from OTEC systems.

EIA does not forecast the commercialization of OTEC systems in its most recent Annual Energy Outlook (March 2010).  However, the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy is currently funding research and development on OTEC cold water pipe manufacturing techniques to help create a more cost-effective OTEC system. 

Chapter 8:Fossil Fuels - Coal, Oil and Natural Gas

Chapter 8: Fossil Fuels - Coal, Oil and Natural Gas

 Where Fossil Fuels Come From

There are three major forms of fossil fuels: coal, oil and natural gas. All three were formed many hundreds of millions of years ago before the time of the dinosaurs – hence the name fossil fuels. The age they were formed is called the Carboniferous Period. It was part of the Paleozoic Era. "Carboniferous" gets its name from carbon, the basic element in coal and other fossil fuels.

The Carboniferous Period occurred from about 360 to 286 million years ago. At the time, the land was covered with swamps filled with huge trees, ferns and other large leafy plants, similar to the picture above. The water and seas were filled with algae – the green stuff that forms on a stagnant pool of water. Algae is actually millions of very small plants.

Some deposits of coal can be found during the time of the dinosaurs. For example, thin carbon layers can be found during the late Cretaceous Period (65 million years ago) – the time of Tyrannosaurus Rex. But the main deposits of fossil fuels are from the Carboniferous Period. For more about the various geologic eras, go towww.ucmp.berkeley.edu/help/timeform.html

As the trees and plants died, they sank to the bottom of the swamps of oceans. They formed layers of a spongy material called peat. Over many hundreds of years, the peat was covered by sand and clay and other minerals, which turned into a type of rock called sedimentary.

More and more rock piled on top of more rock, and it weighed more and more. It began to press down on the peat. The peat was squeezed and squeezed until the water came out of it and it eventually, over millions of years, it turned into coal, oil or petroleum, and natural gas.

 Coal

Coal is a hard, black colored rock-like substance. It is made up of carbon, hydrogen, oxygen, nitrogen and varying amounts of sulphur. There are three main types of coal – anthracite, bituminous and lignite. Anthracite coal is the hardest and has more carbon, which gives it a higher energy content. Lignite is the softest and is low in carbon but high in hydrogen and oxygen content. Bituminous is in between. Today, the precursor to coal—peat—is still found in many countries and is also used as an energy source.

The earliest known use of coal was in China. Coal from the Fu-shun mine in northeastern China may have been used to smelt copper as early as 3,000 years ago. The Chinese thought coal was a stone that could burn.

Coal is found in many of the lower 48 states of U.S. and throughout the rest of the world. Coal is mined out of the ground using various methods. Some coal mines are dug by sinking vertical or horizontal shafts deep under ground, and coal miners travel by elevators or trains deep under ground to dig the coal. Other coal is mined in strip mines where huge steam shovels strip away the top layers above the coal. The layers are then restored after the coal is taken away.

The coal is then shipped by train and boats and even in pipelines. In pipelines, the coal is ground up and mixed with water to make what's called a slurry. This is then pumped many miles through pipelines. At the other end, the coal is used to fuel power plants and other factories.

 Oil or Petroleum

Oil is another fossil fuel. It was also formed more than 300 million years ago. Some scientists say that tiny diatoms are the source of oil. Diatoms are sea creatures the size of a pin head. They do one thing just like plants; they can convert sunlight directly into stored energy.

In the graphic on the left, as the diatoms died they fell to the sea floor (1). Here they were buried under sediment and other rock (2). The rock squeezed the diatoms and the energy in their bodies could not escape. The carbon eventually turned into oil under great pressure and heat. As the earth changed and moved and folded, pockets where oil and natural gas can be found were formed (3).

Oil has been used for more than 5,000-6,000 years. The ancient Sumerians, Assyrians and Babylonians used crude oil and asphalt ("pitch") collected from large seeps at Tuttul (modern-day Hit) on the Euphrates River. A seep is a place on the ground where the oil leaks up from below ground. The ancient Egyptians, used liquid oil as a medicine for wounds, and oil has been used in lamps to provide light.

The Dead Sea, near the modern Country of Israel, used to be called Lake Asphaltites. The word asphalt was derived is from that term because of the lumps of gooey petroleum that were washed up on the lake shores from underwater seeps.

In North America, Native Americans used blankets to skim oil off the surface of streams and lakes. They used oil as medicine and to make canoes water-proof. During the Revolutionary War, Native Americans taught George Washington's troops how to treat frostbite with oil.

As our country grew, the demand for oil continued to increase as a fuel for lamps. Petroleum oil began to replace whale oil in lamps because the price for whale oil was very high. During this time, most petroleum oil came from distilling coal into a liquid or by skimming it off of lakes – just as the Native Americans did.

Then on August 27, 1859, Edwin L. Drake (the man standing on the right in the black and white picture to the right), struck liquid oil at his well near Titusville, Pennsylvania. He found oil under ground and a way that could pump it to the surface. The well pumped the oil into barrels made out of wood. This method of drilling for oil is still being used today all over the world in areas where oil can be found below the surface.

Oil and natural gas are found under ground between folds of rock and in areas of rock that are porous and contain the oils within the rock itself. The folds of rock were formed as the earth shifts and moves. It's similar to how a small, throw carpet will bunch up in places on the floor.

To find oil and natural gas, companies drill through the earth to the deposits deep below the surface. The oil and natural gas are then pumped from below the ground by oil rigs (like in the picture). They then usually travel through pipelines or by ship.

Oil is found in 18 of the 58 counties in California. Kern County, the County where Bakersfield is found, is one of the largest oil production places in the country. But we only get one-half of our oil from California wells. The rest comes from Alaska, and an increasing amount comes from other countries. In the entire U.S., more than 50 percent of all the oil we use comes from outside the country... most of it from the Middle East.

Oil is brought to California by large tanker ships. The petroleum or crude oil must be changed or refined into other products before it can be used.

 Refineries

Oil is stored in large tanks until it is sent to various places to be used. At oil refineries, crude oil is split into various types of products by heating the thick black oil.

Oil is made into many different products – fertilizers for farms, the clothes you wear, the toothbrush you use, the plastic bottle that holds your milk, the plastic pen that you write with. They all came from oil. There are thousands of other products that come from oil. Almost all plastic comes originally from oil. Can you think of some other things made from oil?

The products include gasoline, diesel fuel, aviation or jet fuel, home heating oil, oil for ships and oil to burn in power plants to make electricity. Here's what a barrel of crude oil can make.

In California, 74 percent of our oil is used for transportation – cars, planes, trucks, buses and motorcycles. We'll learn more about transportation energy in Chapter 18.

 Natural Gas

Sometime between 6,000 to 2,000 years BCE (Before the Common Era), the first discoveries of natural gas seeps were made in Iran. Many early writers described the natural petroleum seeps in the Middle East, especially in the Baku region of what is now Azerbaijan. The gas seeps, probably first ignited by lightning, provided the fuel for the "eternal fires" of the fire-worshiping religion of the ancient Persians.

Natural gas is lighter than air. Natural gas is mostly made up of a gas called methane. Methane is a simple chemical compound that is made up of carbon and hydrogen atoms. It's chemical formula is CH4 – one atom of carbon along with four atoms hydrogen. This gas is highly flammable.

Natural gas is usually found near petroleum underground. It is pumped from below ground and travels in pipelines to storage areas. The next chapter looks at that pipeline system.

Natural gas usually has no odor and you can't see it. Before it is sent to the pipelines and storage tanks, it is mixed with a chemical that gives a strong odor. The odor smells almost like rotten eggs. The odor makes it easy to smell if there is a leak.

Energy Safety Note!

If you smell that rotten egg smell in your house, tell your folks and get out of the house quickly. Don't turn on any lights or other electrical devices. A spark from a light switch can ignite the gas very easily. Go to a neighbor's house and call 9-1-1 for emergency help.

 Saving Fossil Fuels

Fossil fuels take millions of years to make. We are using up the fuels that were made more than 300 million years ago before the time of the dinosaurs. Once they are gone they are gone.

So, it's best to not waste fossil fuels. They are not renewable; they can't really be made again. We can save fossil fuels by conserving energy.

In the next chapter read about Natural Gas Distribution System.

Chapter 7:Electricity Transmission System

Chapter 7: Electricity Transmission System

After electricity is produced at power plants it has to get to the customers that use the electricity. Our cities, towns, states and the entire country are criss-crossed with power lines that "carry" the electricity.

As large generators spin, they produce electricity with a voltage of about 25,000 volts. A volt is a measurement of electromotive force in electricity. This is the electric force that "pushes" electrons around a circuit. "Volt" is named after Alessandro Volta, an Italian physicist who invented the first battery.

The electricity first goes to a transformer at the power plant that boosts the voltage up to 400,000 volts. When electricity travels long distances it is better to have it at higher voltages. Another way of saying this is that electricity can be transferred more efficiently at high voltages.

The long thick cables of transmission lines are made of copper or aluminum because they have a low resistance. You'll remember from Chapter 3 that the higher the resistance of a wire, the warmer it gets. So, some of the electrical energy is lost because it is changed into heat energy. High voltage transmission lines carry electricity long distances to a substation.

The power lines go into substations near businesses, factories and homes. Here transformers change the very high voltage electricity back into lower voltage electricity.

From these substations (like in the photo to the right), electricity in different power levels is used to run factories, streetcars and mass transit, light street lights and stop lights, and is sent to your neighborhood.

In your neighborhood, another small transformer mounted on pole (see picture) or in a utility box converts the power to even lower levels to be used in your house. The voltage is eventually reduced to 220 volts for larger appliances, like stoves and clothes dryers, and 110 volts for lights, TVs and other smaller appliances.

Rather than over-head lines, some new distribution lines are underground. The power lines are protected from the weather, which can cause line to break. Have you ever seen what happens after an ice storm?

The picture on the right shows high voltage towers that crumpled from the weight of ice during a 1998 ice storm that hit Canada and parts of the United States. More than 1,000 high voltage towers and 30,000 wooden utility poles were destroyed in Canada by the storm.

Close to 1.4 million people in Quebec and 230,000 in Ontario were without electricity. In many places, power not fully restored for up to a week. Weather people called it the most destructive storm in Canadian history.

When electricity enters your home, it must pass through a meter. A utility company worker reads the meter so the company will know how much electricity you used and can bill you for the cost.

After being metered, the electricity goes through a fuse box into your home. The fuse box protects the house in case of problems. When a fuse (or a circuit breaker) "blows" or "trips" something is wrong with an appliance or something was short- circuited.

 Energy Safety Note!

Never play around a transformer. If a ball or toy lands in or near a transformer, go and tell your parents to call the electric company. The electricity from a transformer could kill you.

Never fly a kite around electrical lines. The kite string could link across the wires, completing a circuit. The electricity could be transferred back to you holding the string.

Never let a balloon - especially a mylar foil balloon - escape into the sky. When the helium of the balloon escapes, the balloon can come down a long way aways. The wire or the mylar surface could stretch across high voltage electrical wires causing problems or even a fire.

You should never touch wires inside or outside your house. You should only let an electrician who knows electricity safety work on the wires.

In the next chapter read about Fossil Fuels - Coal, Oil and Natural Gas

Chapter 6:Generators, Turbines and Power Plants

Chapter 6: Turbines, Generators and Power Plants

As we learned in Chapter 2, electricity flows through wires to light our lamps, run TVs, computers and all other electrical appliances. But where does the electricity come from?

In this chapter, we'll learn how electricity is generated in a power plant. In the next few chapters, we'll learn about the various resources that are used to make the heat to produce electricity. InChapter 7, we'll learn how the electricity gets from the power plant to homes, school and businesses.

Thermal power plants have big boilers that burn a fuel to make heat. A boiler is like a teapot on a stove. When the water boils, the steam comes through a tiny hole on the top of the spout. The moving steam makes a whistle that tells you the water has boiled. In a power plant, the water is brought to a boil inside the boiler, and the steam is then piped to the turbine through very thick pipes.

In most boilers, wood, coal, oil or natural gas is burned in a firebox to make heat. Running through the fire box and above that hot fire are a series of pipes with water running through them. The heat energy is conducted into the metal pipes, heating the water in the pipes until it boils into steam. Water boils into steam at 212 degrees Fahrenheit or 100 degrees Celsius.

The top picture on the right is of a small power plant located at Michigan State University. The black area to the left of the power plant is coal, the energy source that is burned to heat the water in the boilers of this plant.

In the second picture to the left, you'll see the turbine and generator at MSU's power plant. The big pipe on the left side is the steam inlet. On the right side of the turbine is where the steam comes out. The steam is fed under high pressure to the turbine. The turbine spins and its shaft is connected to a turbogenerator that changes the mechanical spinning energy into electricity.

The third picture on the right is of the turbine fan before it is placed inside the turbine housing. You can see a close-up of the turbine blades on the fourth picture. The turbine has many hundreds of blades that are turned at an angle like the blades of a fan. When the steam hits the blades they spin the turbine's shaft that is attached to the bottom of the blades.

After the steam goes through the turbine, it usually goes to a cooling tower outside the where the steam cools off. It cools off and becomes water again. When the hot pipes come into contact with cool air, some water vapor in the air is heated and steam is given off above the cooling towers. That's why you see huge white clouds sometimes being given off by the cooling towers. It's not smoke, but is water vapor or steam. This is not the same steam that is used inside the turbine.

The cooled water then goes back into the boiler where it is heated again and the process repeats over and over.

Most power plants in California use cleaner-burning natural gas to produce electricity. Others use oil or coal to heat the water. Nuclear power plants use nuclear energy to heat water to make electricity. Still others, called geothermal power plants, use steam or hot water found naturally below the earth's surface without burning a fuel. We'll learn about those energy sources in the next few chapters.

 How the Generator Works

The turbine is attached by a shaft to the turbogenerator. The generator has a long, coiled wire on its shaft surrounded by a giant magnet. You can see the inside of the generator coil with all its wires in the picture on the right.

The shaft that comes out of the turbine is connected to the generator. When the turbine turns, the shaft and rotor is turned. As the shaft inside the generator turns, an electric current is produced in the wire. The electric generator is converting mechanical, moving energy into electrical energy.

The generator is based on the principle of "electromagnetic induction" discovered in 1831 by Michael Faraday, a British scientist. Faraday discovered that if an electric conductor, like a copper wire, is moved through a magnetic field, electric current will flow (or "be induced") in the conductor. So the mechanical energy of the moving wire is converted into the electric energy of the current that flows in the wire.

The electricity produced by the generator then flows through huge transmission wires that link the power plants to our homes, school and businesses. If you want to learn about transmission lines, go to Chapter 7.

All power plants have turbines and generators. Some turbines are turned by wind, some by water, some by steam.

In next chapter you can learn about Electricity Transmission System.