Earth s Energy Resources: GeothermaL Geothermal energy comes from heat deep under the ground. This energy is produced in the core of the Earth. The heat from the core can melt rock into magma. The magma heats rocks and water closer to the surface. At about 10,000 feet down, the rocks are hot enough to boil water! Geothermal energy can be captured as steam or hot water. These can be found at hot springs, geysers, and volcanoes. Most geothermal sites are found near hot spots. These are places where magma from deep within the earth comes closer to the surface. In the United States, Hawaii and states in the west have the most geothermal sites. Geothermal energy has been used since ancient Fmes. Ancient NaFve Americans used hot springs for bathing and cooking. The Romans are famous for their bathing palaces. Today, people use water heated by geothermal sources to warm buildings. The hot water is piped in directly. Then, it is carried through the building using insulated pipes. In Reykjavik, Iceland, 95% of the buildings are heated this way. Geothermal energy can also be used to make electricity. The steam turns the turbines on giant generators. The generators produce electricity. California has the most power plants that use geothermal energy. The Geysers in Northern California has been producing electricity this way since 1960. Using geothermal energy to produce electricity is a very clean process. No fuels are burned, so these power plants give off very lirle harmful material. Geothermal power plants release less than 1% of the carbon dioxide given off by power plants that burn fossil fuels. However, geothermal energy is typically available only at its source and cannot be easily stored and transported for use in another place. Also, geothermal plants cost a lot of money to build. ATer use, the water is injected back into the Earth. That makes geothermal energy a renewable
Earth s Energy Resources: Hydroelectricity Hydroelectric energy comes from moving water. SwiTly flowing rivers or falling water can carry large amounts of energy. This energy can be used by machines or for generafng electricity. Many hydropower sources in the US can be found in mountain states in the west and near the Great Lakes. For hundreds of years, water wheels have been used to grind grain and run machinery. The water fills buckets or pushes on paddles to turn the wheel. In some mills, the water falls onto the paddles to push them. In others, the wheel was placed in the water so the current can push the blades. Today, a similar process is used to produce electricity. Water pushes against the blades of a turbine to spin a generator that makes electricity. The first hydroelectric power plant opened in 1882 in Wisconsin. Dams can be built to capture the energy from a river. They can stop the flow of the river and create reservoirs to store the water. The water is released when it is needed. The Grand Coulee Dam in Washington has our nafon s largest hydroelectric facility. The Hoover Dam in Arizona created Lake Meade, the largest man- made lake in the United States. It provides water to desert cifes in Arizona, Nevada, and California. Its power plant supplies electricity to Los Angeles, a city 270 miles away! Hydropower facilifes can change the water temperature and river s flow. This can harm aquafc wildlife. Also, the dams can change where the river flows, and the reservoirs can flood the surrounding land. However, making electricity this way does not release pollufon into the air or produce chemical runoff or toxic waste. Water is returned to the rivers, and the water cycle makes this a renewable
Earth s Energy Resources: Biofuels Biofuels come from living materials. Plants capture energy from the Sun. This energy is transferred to animals when they eat the plants. The most common sources of biofuels are trees, crops, manure, and garbage. People have used biomass for thousands of years to heat their homes and cook their food. One way to release the energy captured in biomass is by burning. UnFl the middle of the 1800 s, people throughout the world burned wood in their homes and factories. Today, wood makes up only a small part of our energy needs in the United States. However, it is sfll used in many countries. All sorts of waste materials can be burned to create steam and electricity. Some sources include corncobs, manure, and household garbage. In waste- to- energy plants, these materials are burned just like coal to make steam. The steam turns the turbines that produce electricity. However, these power plants cost more than convenfonal ones that burn fossil fuels. The energy trapped in garbage can be converted in other ways, too. When dead plants and animals decay, they produce methane. This is a colorless, odorless gas. Wells drilled into some landfills tap into the methane produced there. On farms, manure is put into digesters that separate out the methane gas. It can then be used to produce heat or electricity. Biomass materials can also be changed into transportafon fuels. Biodiesel can be made from vegetable oils and animal fats. In fact, Texas has more biodiesel capacity than any other state in the nafon!* In many US cifes, ethanol made from corn is mixed with gasoline. This gasohol makes a cleaner burning fuel for automobiles. Burning biomass can pollute the air but not as much as fossil fuels do. On the other hand, it reduces the amount of garbage stored in landfills. There will always be plenty of garbage. Plants can be grown over again. This makes biofuels a renewable
Earth s Energy Resources: Wind Wind energy comes from moving air. It is created when the sun heats the Earth. The air over land heats up faster than air above water. The warm air rises and cooler air rushes in to take its place. Wind amounts vary from place to place and season to season. The windiest places are the tops of hills, open plains or shorelines, and gaps between mountains. In Southern California, wind blows more in the summer due to the extreme heafng of the desert during the day. At night, cooler air from the Pacific Ocean rushes in. However, in Montana, the wind blows more in the winter. Texas has the largest wind market in the nafon, responsible for 7.8% of electricity generafon in 2010.* People have harnessed the wind since ancient Fmes. For centuries, sailors have captured the wind in sails to move boats on rivers and oceans. Our early colonists used windmills to grind corn and run sawmills. Farmers and ranchers have used them to pump water from wells. Today, we use windmills to generate electricity. Like old- fashioned windmills, modern machines use blades to collect the wind s energy. Wind pushing on the blades, making them turn. These turbines are connected to generators that produce electricity. Modern wind machines can be as tall as a 20- story building. Each blade can span 200 feet across. At wind farms, dozens of windmills cover a large area. The world s largest wind farm is in Texas and has 421 wind machines! Wind machines can only run when the wind blows about 14 mph or more. At most wind farms, the wind is only right for producing electricity about two- thirds of the Fme. However, windmills are a clean energy source. No fuels are burned, so no pollufon is created. On the other hand, as long as the sun shines, there will be wind. That makes wind energy a renewable
Earth s Energy Resources: Solar Solar energy comes from the sun. Every day the sun sends out enormous amounts of energy. Life on Earth depends on the sun s energy. Directly or indirectly, the sun is the source of all the types of energy we use. Energy from the sun drives the water cycle and causes weather. That gives us water and wind energy. Through photosynthesis, plants capture and store energy from the sun. That energy is passed to organisms that eat the plants. Those living sources give us the biomass for biofuels. Even fossil fuels came from the remains of ancient plants and animals. We can use the Sun s energy to warm spaces or heat water. A closed car on a sunny day traps the Sun s thermal energy. Some homes are specially designed to collect the Sun s light and warmth, with large windows facing south. Others have special collectors, made of dark metal plates covered with glass. The boxes are mounted on the roof, and air or water flows through them. Then the warmed air or water is piped through the house. Solar water heaters work in a similar way. Sunlight heats water in tanks. Solar energy can also be used to produce electricity. At solar thermal power plants, curved mirrors reflect sunlight onto a pipe that contains a special liquid. When the liquid is heated, it is used to produce steam for generators that make electricity. The largest solar power plants in the world are located in California s Mojave Desert. Texas, however, is also a leader in the amount of electricity it can produce from solar energy. West Texas alone has 75% more exposure to direct sunlight than East Texas, making it a good place for projects supporfng energy producfon from sunlight.* Another way to produce electricity from sunlight is through photovoltaic cells, which are made with silicon. Electricity is generated when sunlight hits these special cells. The energy can be used directly or stored in bareries. The first photovoltaic cells were made for space satellites in the 1950 s. Solar energy is clean, since no fuels are burned. The amount of solar energy available depends on the Fme of day, season, weather condifons, and our locafon on Earth, and there s no sunlight available at night! However, the sun will confnue to shine for billions of years, making this a renewable