Chapter 11:Geothermal Energy

Chapter 11: Geothermal Energy

Geothermal Energy has been around for as long as the Earth has existed. "Geo" means earth, and "thermal" means heat. So, geothermal means earth-heat.

Have you ever cut a boiled egg in half? The egg is similar to how the earth looks like inside. The yellow yolk of the egg is like the core of the earth. The white part is the mantle of the earth. And the thin shell of the egg, that would have surrounded the boiled egg if you didn't peel it off, is like the earth's crust.

Below the crust of the earth, the top layer of the mantle is a hot liquid rock called magma. The crust of the earth floats on this liquid magma mantle. When magma breaks through the surface of the earth in a volcano, it is called lava.

For every 100 meters you go below ground, the temperature of the rock increases about 3 degrees Celsius. Or for every 328 feet below ground, the temperature increases 5.4 degrees Fahrenheit. So, if you went about 10,000 feet below ground, the temperature of the rock would be hot enough to boil water.

Deep under the surface, water sometimes makes its way close to the hot rock and turns into boiling hot water or into steam. The hot water can reach temperatures of more than 300 degrees Fahrenheit (148 degrees Celsius). This is hotter than boiling water (212 degrees F / 100 degrees C). It doesn't turn into steam because it is not in contact with the air.

When this hot water comes up through a crack in the earth, we call it a hot spring, like Emerald Pool at Yellowstone National Park pictured on the left. Or, it sometimes explodes into the air as a geyser, like Old Faithful Geyser pictured on the right.

About 10,000 years ago, Paleo-Indians used hot springs in North American for cooking. Areas around hot springs were neutral zones. Warriors of fighting tribes would bathe together in peace. Every major hot spring in the United States can be associated with Native American tribes. California hot springs, like at the Geysers in the Napa area, were important and sacred areas to tribes from that area.

In other places around the world, people used hot springs for rest and relaxation. The ancient Romans built elaborate buildings to enjoy hot baths, and the Japanese have enjoyed natural hot springs for centuries.

 Geothermal Today

Today, people use the geothermally heated hot water in swimming pools and in health spas. Or, the hot water from below the ground can warm buildings for growing plants, like in the green house on the right.

In San Bernardino, in Southern California, hot water from below ground is used to heat buildings during the winter. The hot water runs through miles of insulated pipes to dozens of public buildings. The City Hall, animal shelters, retirement homes, state agencies, a hotel and convention center are some of the buildings which are heated this way.

In the Country of Iceland, many of the buildings and even swimming pools in the capital of Reykjavik (RECK-yah-vick) and elsewhere are heated with geothermal hot water. The country has at least 25 active volcanoes and many hot springs and geysers.

 Geothermal Electricity

Hot water or steam from below ground can also be used to make electricity in a geothermal power plant.

In California, there are 14 areas where we use geothermal energy to make electricity. The red areas on the map show where there are known geothermal areas. Some are not used yet because the resource is too small, too isolated or the water temperatures are not hot enough to make electricity.

The main spots are:

• The Geysers area north of San Francisco
• In the northwest corner of the state near Lassen Volcanic National Park
• In the Mammoth Lakes area - the site of a huge ancient volcano
• In the Coso Hot Springs area in Inyo County
• In the Imperial Valley in Southern California.

Some of the areas have so much steam and hot water that it can be used to generate electricity. Holes are drilled into the ground and pipes lowered into the hot water, like a drinking straw in a soda. The hot steam or water comes up through these pipes from below ground.

You can see the pipes running in front of the geothermal power plant in the picture. This power plant is Geysers Unit # 18 located in the Geysers Geothermal area of California.

A geothermal power plant is like in a regular power plant except that no fuel is burned to heat water into steam. The steam or hot water in a geothermal power plant is heated by the earth. It goes into a special turbine. The turbine blades spin and the shaft from the turbine is connected to a generator to make electricity. The steam then gets cooled off in a cooling tower.

The white "smoke" rising from the plants in the photograph above is not smoke. It is steam given off in the cooling process. The cooled water can then be pumped back below ground to be reheated by the earth.

Here's a cut-away showing the inside of the power plant. The hot water flows into turbine and out of the turbine. The turn turns the generator, and the electricity goes out to the transformer and then to the huge transmission wires that link the power plants to our homes, school and businesses. We learned about transmission lines in Chapter 7.

California's geothermal power plants produce about one-half of the world's geothermally generated electricity. The geothermal power plants produce enough electricity for about two million homes.

 Geothermal / Ground Source Heat Pumps

Though it gets much hotter as we go deep below ground, the upper layer of the earth close to the surface is not very hot.

Almost everywhere across the entire planet, the upper 10 feet below ground level stays the same temperature, between 50 and 60 degrees Fahrenheit (10 and 16 degrees C). If you've ever been in a basement of a building or in a cavern below ground, the temperature of the area is almost always cool.

A geothermal or ground source heat pump system can use that constant temperature to heat or cool a building. Pipes are buried in the ground near the building. Inside these pipes a fluid, like the antifreeze in a car radiator, is circulated.

In winter, heat from the warmer ground goes through the heat exchanger of a heat pump, which sends warm air into the home or business. During hot weather, the process is reversed. Hot air from inside the building goes through the heat exchanger and the heat is passed into the relatively cooler ground. Heat removed during the summer can also be used to heat water.

For another FLASH "movie" about how ground source heat pumps work, go to the GeoExchange website at:http://www.ghpc.org/about/movie.htm.

Learn about Hydro Power in the next chapter.

Chapter 10:Biomass Energy

 Chapter 10: Biomass Energy

Biomass is matter usually thought of as garbage. Some of it is just stuff lying around -- dead trees, tree branches, yard clippings, left-over crops, wood chips (like in the picture to the right), and bark and sawdust from lumber mills. It can even include used tires and livestock manure.

Your trash, paper products that can't be recycled into other paper products, and other household waste are normally sent to the dump. Your trash contains some types of biomass that can be reused. Recycling biomass for fuel and other uses cuts down on the need for "landfills" to hold garbage.

This stuff nobody seems to want can be used to produce electricity, heat, compost material or fuels. Composting material is decayed plant or food products mixed together in a compost pile and spread to help plants grow.

California produces more than 60 million bone dry tons of biomass each year. Of this total, five million bone dry tons is now burned to make electricity. This is biomass from lumber mill wastes, urban wood waste, forest and agricultural residues and other feed stocks.

If all of it was used, the 60 million tons of biomass in California could make close to 2,000 megawatts of electricity for California's growing population and economy. That's enough energy to make electricity for about two million homes!

How biomass works is very simple. The waste wood, tree branches and other scraps are gathered together in big trucks. The trucks bring the waste from factories and from farms to a biomass power plant. Here the biomass is dumped into huge hoppers. This is then fed into a furnace where it is burned. The heat is used to boil water in the boiler, and the energy in the steam is used to turn turbines and generators (see Chapter 8).

Biomass can also be tapped right at the landfill with burning waster products. When garbage decomposes, it gives off methane gas. You'll remember in chapters 8 and 9 that natural gas is made up of methane. Pipelines are put into the landfills and the methane gas can be collected. It is then used in power plants to make electricity. This type of biomass is called landfill gas.

A similar thing can be done at animal feed lots. In places where lots of animals are raised, the animals - like cattle, cows and even chickens - produce manure. When manure decomposes, it also gives off methane gas similar to garbage. This gas can be burned right at the farm to make energy to run the farm.

Using biomass can help reduce global warming compared to a fossil fuel-powered plant. Plants use and store carbon dioxide (CO2) when they grow. CO2 stored in the plant is released when the plant material is burned or decays. By replanting the crops, the new plants can use the CO2 produced by the burned plants. So using biomass and replanting helps close the carbon dioxide cycle. However, if the crops are not replanted, then biomass can emit carbon dioxide that will contribute toward global warming.

So, the use of biomass can be environmentally friendly because the biomass is reduced, recycled and then reused. It is also a renewable resource because plants to make biomass can be grown over and over.

Today, new ways of using biomass are still being discovered. One way is to produce ethanol, a liquid alcohol fuel. Ethanol can be used in special types of cars that are made for using alcohol fuel instead of gasoline. The alcohol can also be combined with gasoline. This reduces our dependence on oil – a non-renewable fossil fuel.

Next chapter is about Geothermal Energy.

Chapter 9:Natural Gas Distribution System

Chapter 9: Natural Gas Distribution System

We learned in Chapter 8 that natural gas is a fossil fuel. It is a gaseous molecule that's made up of two atoms – one carbon atom combined with four hydrogen atom. It's chemical formula is CH4. The picture on the right is a model of what the molecule could look like.

Don't confuse natural gas with "gasoline," which we call "gas" for short. Like oil, natural gas is found under ground and under the ocean floor. Wells are drilled to tap into natural gas reservoirs just like drilling for oil. Once a drill has hit an area that contains natural gas, it can be brought to the surface through pipes.

The natural gas has to get from the wells to us. To do that, there is a huge network of pipelines that brings natural gas from the gas fields to us. Some of these pipes are two feet wide.

Natural gas is sent in larger pipelines to power plants to make electricity or to factories because they use lots of gas. Bakeries use natural gas to heat ovens to bake bread, pies, pastries and cookies. Other businesses use natural gas for heating their buildings or heating water.

From larger pipelines, the gas goes through smaller and smaller pipes to your neighborhood.

In businesses and in your home, the natural gas must first pass through a meter, which measures the amount of fuel going into the building. A gas company worker reads the meter and the company will charge you for the amount of natural gas you used.

Energy can be found in a number of different forms. It can be chemical energy, electrical energy, heat (thermal energy), light (radiant energy), mechanical energy, and nuclear energy.

In some homes, natural gas is used for cooking, heating water and heating the house in a furnace.

In rural areas, where there are no natural gas pipelines, propane (another form of gas that's often made when oil is refined) or bottled gas is used instead of natural gas. Propane is also called LPG, or liquefied petroleum gas, is made up of methane and a mixture with other gases like butane.

Propane turns to a liquid when it is placed under slight pressure. For regular natural gas to turn into a liquid, it has to be made very, very cold.

Cars and trucks can also use natural gas as a transportation fuel, but they must carry special cylinder-like tanks to hold the fuel.

When natural gas is burned to make heat or burned in a car's engine, it burns very cleanly. When you combine natural gas with oxygen (the process of combustion), you produce carbon dioxide and water vapor; plus the energy that's released in heat and light.

Some impurities are contained in all natural gas. These include sulphur and butane and other chemicals. When burned, those impurities can create air pollution. The amount of pollution from natural gas is less than burning a more "complex" fuel like gasoline. Natural gas-powered cars are more than 90 percent cleaner than a gasoline-powered car.

That's why many people feel natural gas would be a good fuel for cars because it burns cleanly.

Next chapter is about Biomass Energy.

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.

BACK TO TOP

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.

BACK TO TOP

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.

BACK TO TOP

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.

BACK TO TOP

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.

BACK TO TOP

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.