How electric energy is generated - Referat
How electric energy is generated
One of the laws of nature is that energy can neither be created nor destroyed but ist form can be changed. We have managed to change the form of energy in such a way that it can do work for us. Energy lights our houses and cities. Energy powers our cars, trains, and planes. It warms our homes, cooks our food and it enables us to listen to the radio and to watch television. Energy powers the machinery in our factories.
Energy is defined as “the ability to do work.”
Although most of our vehicles (cars, trucks, planes, ships) are powered by energy that is based on oil, the majority of the devices we use in our households and the machinery that produces the goods in our factories are powered by electric energy.
Electric energy is generated in power plants. There are different kinds of power plants, but the biggest an most common ones are big boilers that burn fuel to produce heat energy. This kind of power plant is called a thermal power station. Even nuclear power plants belong to this kind. The heat is used to boil water into steam which then is led to a turbine to make the turbine spin. The turbine’s shaft is connected to a generator that changes the mechanical spinning energy into electricity.
Let us look at the cross section of a power plant (picture): In most boilers coal, oil, or natural gas are used to produce heat. Above a hot fire there is a series of pipes with water running through them. The heat energy is conducted into metal pipes, heating the water until it boils into steam. The steam (red line) then goes to the turbines under high pressure. The turbine has many blades that look like the blades of a fan. When the steam hits the blades they spin a shaft that is attached to the bottom of the blades.
The turbine’s shaft is attached to the generator which is also made to spin in this way. The generator has a gigant magnet inside a stationary ring which is wrapped with a long wire. When the magnet inside the generator turns, an electric voltage is produced in the wire. This process, which is called induction, always takes place when a wire or any electrically conductive material moves across magnetic field.
After having left the turbine, the steam goes to a condenser where is cools off and so becomes water again. Pumps make it go back to the boiler (blue line) where it is heated again and the process repeats itself over and over. To condense the steam back into water, millions of litres of cooling water are needed every hour. That is the reason why power plants are usually located at rivers or lakes. Big cooling towers are needed to cool off the cooling water. When the hot pipes in the cooling towers come into contact with cool air, vapour in the air is heated and steam is given off above the cooling towers. However, this is not the same steam that is used inside the turbine.
Nuclear power plants work similarly. The difference is that they use uranium as “fuel” to boil water into steam. Inside the reactor of an atomic power plant, uranium atoms are split in a controlled chain reaction. This process is called nuclear fission.
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