Generating Electricity

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  • Created by: Hope
  • Created on: 11-06-13 20:07

Fossil Fuels

The fossil fuels are coal, oil and natural gas. They were formed from the remains of living organisms millions of years ago and they release heat energy when they are burned. They are non-renewable. This chart shows an energy transfer diagram for the generation of electricity from a fossil fuel such as coal.

  • Coal - Store of chemical energy
  • Energy transferred as heat 
  • Water and Steam- Store of heat energy 
  • Energy transferred as movement 
  • Turbine 
  • Energy transferred as movement 
  • Generator
  • Energy transferred as electricity 

Disadvantages- Their supply is limited and they will eventually run out. Coal and oil release sulfur dioxide gas when they burn, which causes breathing problems for living creatures and contributes to acid rain. Release carbon dioxide when they burn, adding to greenhouse effect and global warming

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Fossil Fuels 2

Carbon Capture 

Carbo capture and storage is a way to prevent cabron dioxide building up in the atmosphere. It is a rapidly evolving technology that involves seperating carbon dioxide from the waste gases. The carbon dioxide is then stored undeerground, for example in old oil feilds such as those found under the north sea.

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Nuclear Fuels

The main nuclear fuels are uranium and plutomium. These are radioactive metals. Nuclear fuels are not burn to relase energy. Instead, nuclear fission reactions (where the nuclei in atoms are split_ in the fuels release heat energy.

The rest of the process of generating electricity is then identical to the process using fossil fuels. The heat energy is used to boil water. The kinetic energy in the expanding steam spins turbines. which then drive generators to produce electricity.

Advantages 

Unlike fossil fuels, nuclear fuels do not produce carbon dioxide or sulfur dioxide 

Disadvantages 

Fossil fuels, nuclear fuels are non-renewable energy resources. If there is an accident, large amount of radioactive material could be released into the environment. In addition, nuclear waste remains radioactive and is hazardous to health for thousands of years. 

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Wind Energy

The wind is produced as a result of giant convection currents in the earths atomosphere, which are driven by heat energy from the sun. This means that the kinetic energy in wind is a renewable energy resource: as long as the sun exists, the wind will too.

Wind Turbines 

Wind turbines use the wind to drive turbines directly. The have huge blades mounted on a tall tower. The blades are connected to a 'nacelle' or housing, which contains gears linked to a generator. As the wind blows, it transfers some of its kinetic energy to the blades which turn and drive the generator.

Advantages 

Wind is a renewable energy resource and there are no fuel costs. No harmful polluting gases are produced.

Disadvantages 

Wind farms are noisy and may spoil the veiw for people living near them. The amount of electricity generated depends on the strength of the wind. If there is no wind, no electricity 

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Water Energy

Like the wind, water is used to drive turbines directly. There are several ways that water can be used, including waves, tides and falling water in hydroelectric power schemes.

Wave 

The water in the sea rises and falls because of the waves on the surface. Wave machines used the kinetic energy in this movement to drive electricity generators.

Tides 

Huge amounts of water move in and out of river mouths each day because of the tides. A tidal barrage is a barrier built over a river estuary to make use of the kinetic energy in the moving water. The barrage contains electricity generators which are driven by the water rushing through tubesin the barrage 

Hydroelectic power

Like tidal barrages, hydroelectic power (HEP) stations use the kinetic energy in moving water. But the water comes from behind a dam build across a river valley. The water high up behind the dam contains gravitational potential energy. This is transferred to kinetic energy as the water rushes down through the tubes inside the dam. The water drives electrical generators

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Wave Energy 2

Advantages 

Water power in its various forms is a renewable energy resource and there are no fuel costs. No harmful polluting gases are produced. Tidal barrages and hydroelectric power stations are very reliable and can be easily switched one

Disadvantages

It has been difficult to scale up the deigns for wave machines to produce large amounts of electricity. Tidal barrages destory the habitat of esturary species, including wading birds, hydroelectricity  dam flood farmland and push people from their homes. The rotting vegetation underwater releases methane, which is a greenhouse gas

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Geothermal Energy

Hot water and steam from deep underground can be used to drive turbines. This is geothermal energy

Volcanic Areas

  • Several types of rock contain radioactive substances such as uranium.
  • Radioactive decay of these substances releases heat energy, which warms up the rocks.
  • In volcanic areas the rocks may heat water so that it rises to the surface naturally as hot water and steam 
  • Here the steam can be used to drive turbines and electricity generators

Hot Rocks

In some places, where the rocks are hot, but no hot water or steam rises to the surface. In this situation deep wells can be drilled down to the hot rocks and cold water pumped down. The water runs through fractures in the rocks and is heated up/ It returns to the sruface as hot water and steam, where its energy can be used to drive turbines and elecricty generators 

Renerwable energy resource, no fuel costs// Most parts of the world fo no have suitable areas where geothermal energy can be exploited 

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Solar Energy

Solar cells are devices that convert light energy directly into eletrical energy. Do not confuse solar cells with solar panels, which use heat energy from the sun to heat up water.

Large arrays of solar cels are used in power road signs in remote areas and even larger arrays are used to power satellites in orbit around the earth 

Advantages 

Solar energy is renewable energy resource and there are no fuel costs. No harmful polluting gases are produced. Solar cells provide electricity in remote locations, such as roadside signs.

Disadvantages

Solar cells are expensive and inefficent, so the cost of their electricity is high. So;ar cells do not work at night.

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Generating Electricity

Power stations

Power stations fuelled by fossil fuels or nuclear fuels are reliable sources of energy, meaning they can provide power whenever it is needed. However, their start-up times vary according to the type of fuel used.

  • Nuclear power stations and coal-fired power stations usually provide 'base load' electricity - they are run all the time because they take the longest time to start up. 
  • Oil-fired and gas-fired power stations are often used to provide extra electricity at peak times, because they take the least time to start up.

Renewable Resources 

Do not cost anything, but the equipment used to generate the power may be expensive to build. Certain resources are reliable, including tidal barrages and hydroelectiv power. Others are less reliable including wind and solar energy 

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The National Grid

Transformers

  • Electricity is transferred from power stations to consumers through the wires and cables of the national grid 
  • When a current flows through a wire some energy is lost as heat
  • The higher the current the more heat is lost 
  • To reduce these losses the national grid transmits electricity at a low current, this needs a high voltage 
  • Transformers are used in the nationla grid. A transformer is an electical devise that changes the voltage of an alternating current (ac) supply, such as the mains elecrtical supply a transformer that:
  • Increases the voltage is called a step-up transformer 
  • Decreases the voltage is a step-down transformer 
  • Step up trnasformers change the voltage to the very values needed to tranmit electricity through the National Grid power lines. 
  • Step down transformers are used locally to reduce the voltage to safe levels. 
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National Grid 2

(http://www.bbc.co.uk/schools/gcsebitesize/science/images/aqa_phy_national_grid.jpg)

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