Tuesday 24 November 2015

how power coal fired plant work


A power station is really a machine that extracts energy from a fuel. Some power stations burn fossil fuels such as coal, oil, or gas.Nuclear power stations produce energy by splitting apart atoms of heavy materials such as uranium and plutonium. The heatproduced is used to convert water into steam at high pressure. This steam turns a windmill-like device called a turbine connected to an electricity generator. Extracting heat from a fuel takes place over a number of stages and some energy is wasted at each stage. That means power plants are not very efficient: in a typical plant running on coal, oil, or gas, only about 30–40 percent of the energy locked inside the fuel is converted to electricity and the rest is wasted.
Left: Power plant transformers. Right: Power plant pylon transmission lines
Power station transformers                                    Transmission line
  1. Fuel: The energy that finds its way into your TV,computer, or toaster starts off as fuel loaded into a power plant. Some power plants run on coal, while others use oil, natural gas, or methane gas from decomposing rubbish.
  2. Furnace: The fuel is burned in a giant furnace to release heat energy.
  3. Boiler: In the boiler, heat from the furnace flows around pipes full of cold water. The heat boils the water and turns it into steam.
  4. Turbine: The steam flows at high-pressure around a wheel that's a bit like a windmill made of tightly packed metal blades. The blades start turning as the steam flows past. Known as a steam turbine, this device is designed to convert the steam's energy into kinetic energy (the energy of something moving). For the turbine to work efficiently, heat must enter it at a really high temperature and pressure and leave at as low a temperature and pressure as possible.
  5. Cooling tower: The giant, jug-shaped cooling towers you see at old power plants make the turbine more efficient. Boiling hot water from the steam turbine is cooled in a heat exchanger called a condenser. Then it's sprayed into the giant cooling towers and pumped back for reuse. Most of the water condenses on the walls of the towers and drips back down again. Only a small amount of the water used escapes as steam from the towers themselves, but huge amounts of heat and energy are lost.
  6. Generator: The turbine is linked by an axle to a generator, so the generator spins around with the turbine blades. As it spins, the generator uses the kinetic energy from the turbine to make electricity.
  7. Electricity cables: The electricity travels out of the generator to a transformer nearby.
  8. Step-up transformer: Electricity loses some of its energy as it travels down wire cables, but high-voltage electricity loses less energy than low-voltage electricity. So the electricity generated in the plant is stepped-up (boosted) to a very high voltage as it leaves the power plant.
  9. Pylons: Hugh metal towers carry electricity at extremely high voltages, along overhead cables, to wherever it is needed.
  10. Step-down transformer: Once the electricity reaches its destination, another transformer converts the electricity back to a lower voltage safe for homes to use.
  11. Homes: Electricity flows into homes through underground cables.
  12. Appliances: Electricity flows all round your home to outlets on the wall. When you plug in a television or other appliance, it could be making a very indirect connection to a piece of coal hundreds of miles away!

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