How Electricity is made: PART ONE- COAL

Modern life is unimaginable without electricity. Electrical energy powers our homes, buildings and streets. For a source of energy to end up as electricity it may undergo many transformations. You may have herd the simple term

“Energy cannot be created or destroyed; it can only be changed from one form to another”

Energy exists in many different forms. Examples of these are: light energy, heat energy, mechanical energy, gravitational energy, electrical energy, sound energy, chemical energy, nuclear or atomic energy and so on. These forms of energy can be transferred and transformed between one another.

OLYMPUS DIGITAL CAMERAWe get electricity, from the conversion of other sources of energy, like coal, nuclear power, natural gas, Solar Power, Wind Power and Hydro-electricity. Most electrical energy is created in a Power Station (Steam Power Plant) before it can power our homes and streets. A power station contains large machines called turbines, which are turned very quickly. Power stations need large amounts of energy to turn the turbines.

PART ONE: COAL

Coal is a fuel that is found in the ground. Over millions of years, accumulated plant and animal matter is covered by sediment and stored within the earth’s crust, gradually being transformed into hard black solids by the sheer weight of the earth’s surface, producing coal. The energy in the coal came from the suns energy that was stored in the plants. When the coal is burned, it gives up that energy as heat. The coal’s heat energy can then be turned into electrical energy. This process is described below.

  1. First the coal is mined to a fine powder and transported to a Power Station.
  2. Then the coal is burned in a boiler which causes the water in the boiler pipes to become steam.
  3. The steam spins the turbine blades.
  4. The spinning blades turn a shaft connected to a generator.
  5. When it nears the point of consumption, such as our homes, the electricity is transformed down to the safer 100-250 voltage systems used in the domestic market.
  6. Steam  Power Plant: The high pressure steam is passed into a turbine.
  7. In the generator, big magnets spin close to coils of wire.
  8. When this happens, electrical current is produced in the wires.
  9. The electricity generated is transformed into the higher voltages (up to 400,000 volts) used for      economic, efficient transmission via power line grids.

Coal and the environment:

Coal, like other fossil fuel supplies, takes millions of years to create, but releases its stored energy within only a few moments when burned to generate electricity. Because coal is a finite resource, and cannot be replenished once it is extracted and burned, it cannot be considered a renewable resource.

The burning of coal is the most polluting method for producing electricity. The popularity of coal is largely due to its low cost. However the environmental impacts are considerable. Besides the production of greenhouse gases by burning coal, there are also many other harmful compounds released during this process. The extraction, transportation, storage and disposal of coal all create additional environmental issues.

Environmental Impact:

  • Acid Rain: Emissions of Sulfur dioxide and nitrogen oxide spawn acid rain in many countries.
  • Smog: Coal emissions also cause urban smog, which has been linked to respiratory ailments, and coal-fired power plants also contribute to global climate change.

image-13 Increase CO2 Greenhouse effect: Coal plants emit tons of carbon dioxide into the atmosphere from electricity generators.

This is an interesting Artical to read: Aust power stations among world’s worst CO2 polluters……CLICK HERE TO FOLLOW LINK  

By releasing the energy stored in coal, large quantities of carbon dioxide that have been stored in the coal for millions of years are released back into the atmosphere, increasing the threat of global warming. Coal plants are also a major source of airborne emissions of mercury, a toxic heavy metal.

 

Coal MiningMining and Transportation: The mining, processing, and transporting of coal also insults the environment. Coal is removed from the earth through strip mining, which can contaminate soils with heavy metals and destroy near-surface aquifers. Sometimes Coal is mined by removing entire mountain tops to more easily extract the subsurface mineral reserves.

  • Waste: Coal combustion also results in huge quantities of solid wastes. The waste created from the burning process is also very harmful to the environment. The sludge from smoke stack scrubbers is toxic, containing a number of heavy metals that can potentially contaminate the environment. As much of this waste is stored on site at the power plant, it can easily enter the water supply of the surrounding area. The water used to cool the coal burning equipment is often sourced from a local water body and then simply pumped back after it has been used. This hot water, often containing chlorine or other chemicals, can then cause algal blooms and other environmental problems.

Coal and energy efficiency

Factors which affect the efficiency of power stations include fuel type (brown coal, black coal, gas) the load factor (full load, part load) and the technology employed. Coal-fired power stations are not very efficient. Most of them don’t reach more than 40% efficient. A few can reach 45%. There is a theoretical limit to the percentage of energy that can be converted from heat to mechanical energy in any heat engine, which is the first part of what a coal-fired power station does. This limit depends on the difference in temperature between the heat source (burning coal) and the heat sink (the steam coming out the end of the turbine). The higher the difference in temperature, the more efficient. If you use a higher or lower grade of coal, or burn it in a more or less efficient coal-fired power plant, it might take as little as 0.4 kilograms per kilowatt hour. Or it might take as much as 0.7 kilograms. A Wikipedia article suggests a figure of  438 kilograms of coal for 876 kilowatt hours, which is 0.43 kilograms per kilowatt hour.

KONICA MINOLTA DIGITAL CAMERAAuthor Rachel McCann

Photovoltaic Lighting Group

 

By understanding the different processes of creating electricity we are able to use the most sustainable methods for everyday use such as lighting our streets and Parks. At PLG we specialise in being able to custom design standalone solar lighting system for our customers’ requirements.

LIGHTING THE WAY OF THE FUTURE

 

Categories: Sustainability

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