2017-11-01
1131
Geothermal Energy has been around for as long as the Earth has existed. The centre of the Earth is around 6000 degrees Celsius – hot enough to melt rock. Even a few kilometers down, the temperature can be over 250 degrees Celsius. In general, the temperature rises one degree Celsius for every 36 meters you go down. In volcanic areas, molten rock can be very close to the surface. Geothermal energy has been used for thousands of years in some countries for cooking and heating. The name "geothermal" comes from two Greek words: "geo" means "Earth" and "thermal" means "heat".
Today, people use the geothermal 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 a green house. 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 which are heated this way. Hot water or steam from below ground can also be used to make electricity in a geothermal power plant. 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. Geothermal energy does not produce any pollution, and does not contribute to the greenhouse effect. But the big problem is that there are not many places where you can build a geothermal power station and you need hot rocks of a suitable type, at a depth where we can drill down to them. The type of rock above is also important, it must be of a type that we can easily drill through.
The first geothermal power station was built at Landrello, in Italy, and the second was at Wairekei in New Zealand. Others are in Iceland, Japan, the Philippines and the United States.
Text 8. HYDRO POWER
When it rains in hills and mountains, the water becomes streams and rivers that run down to the ocean. The moving or falling water can be used to do work. Energy is the ability to do work. So moving water can be used to make electricity. Hydro means water. Hydro-electric means making electricity from water power.
For hundreds of years, moving water was used to turn wooden wheels that were attached to grinding wheels to grind (or mill) flour or corn. These were called grist mills or water mills. The first use of water to generate electricity was in 1882 on the Fox river, in the USA, which produced enough power to light two paper mills and a house.
Today, moving water can also be used to make electricity. Hydroelectric power uses the kinetic energy of moving water to make electricity. Dams can be built to stop the flow of a river. Water behind a dam often forms a reservoir. Dams are also built across larger rivers but no reservoir is made. The river is simply sent through a hydroelectric power plant.
The water behind the dam flows through the intake and into a pipe called a penstock. The water pushes against blades in a turbine, causing them to turn. The turbine spins a generator to produce electricity. The electricity can then travel over long distance electric lines to your home, to your school, to factories and businesses.
Nowadays there are many hydro-electric power stations, providing around 20% of the world's electricity. Hydro is one of the largest producers of electricity in the United States. Water power supplies about 10 percent of the entire electricity that we use. In states with high mountains and lots of rivers, even more electricity is made by hydro power. In California, for example, about 15 percent of all the electricity comes from hydroelectric. The state of Washington leads the nation in hydroelectricity. About 87 percent of the electricity made in Washington state is produced by hydroelectric facilities. Some of that electricity is exported from the state and used in other states.
Text 9. SOLAR ENERGY
We have always used the energy of the sun as far back as humans have existed on this planet. As far back as 5,000 years ago, people "worshipped" the sun. Ra, the sun-god, who was considered the first king of Egypt. In Mesopotamia, the sun-god Shamash was a major deity and was equated with justice. In Greece there were two sun deities, Apollo and Helios. The influence of the sun also appears in other religions - Roman religion, the Druids of England, the Aztecs of Mexico, the Incas of Peru and many Native American tribes.
We know today, that the sun is simply our nearest star. Without it, life would not exist on our planet. We use the sun's energy every day in many different ways. When we hang laundry outside to dry in the sun, we are using the sun's heat to do work - drying our clothes. Plants use the sun's light to make food. Animals eat plants for food. Decaying plants hundreds of millions of years ago produced the coal, oil and natural gas that we use today. So, fossil fuels is actually sunlight stored millions and millions of years ago.
Indirectly, the sun or other stars are responsible for all our energy. Even nuclear energy comes from a star because the uranium atoms used in nuclear energy were created in the fury of a nova - a star exploding. Solar energy can also be used to make electricity. Solar cells convert sunlight directly into electricity. They are made of semiconducting materials similar to those used in computer chips. When sunlight is absorbed by these materials, the solar energy knocks electrons loose from their atoms, allowing the electrons to flow through the material to produce electricity. This process of converting light (photons) to electricity (voltage) is called the photovoltaic effect. In a sunny climate, you can get enough power to run a 100W light bulb from just one square meter of solar panel.
Solar cells provide the energy to run satellites that orbit the Earth. These give us satellite TV, telephones, navigation, weather forecasting, the Internet and all manner of other facilities.
three feet away - на расстоянии трех футов
