- Energy is transferred from cells and other sources.
- Power is the rate of energy transfer.
- Power is usually measured in watts (W), or kilowatts (kW). 1kW = 1000W.
- Energy transferred(J) = Power(W) X Time(S)
- Cost = number of kWh X cost per kWh
- Power(W) = voltage(V) X current(A)
- More efficent machines waste less energy.
- Efficency = energy usefully transferred/ total energy supplied X 100%
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Saving energy and energy sources
- Installing loft-insulation, double glazing and draugh-proofing reduces the heat los through gaps in walls, ceilings, windows, and around doors in our homes.
- The methods that save the most money each year are considered the most effective, but cost effective depends on timescale
- The government can encourage people to save energy by offering grants for better home insulations and improving public transport.
- Electricity is a secondry energy sourse because it is produced using other energy sources, e.g, coal, nuclear, fuel, wind power, these are primary energy sources.
- Non-renewable sources; Fossil fuels and Nuclear fuels. These will run out and do all the damage to the environment.
- Renewable sources; Wind, Waves, Tides, Hydroeletric, Biofuels, Geothermal, Solar. These will never run out and do less damage to the environmemt.
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- Most of the electricity we ue is generated by using primary energy sources to heat water in power stations. These are called thermal power stations.
- Energy is released from the fuel, usually by burning in a boiler, and used to generate steam. The steam turns a turbine. A generator converts the movement of the turbine, (kinetic) into electricity.
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- Nuclear power stations release energy by splitting atoms.
- In nuclear fission, atoms in the nuclear fuel are split in two, releasing lots of heat energy. Water is used as a coolant to take away the heat produced by the fission. This produces steam which drives a turbine.
- Advantages of nuclear energy; It releases a lot more energy than burning. It doesn't produce carbon dioxide. It is relatively cheap.
- Disadvantages; Produces radioactive waste that is difficult and dangerous to dispose of as it imits ionising radiation. Radioactive waste can put people at risk this is because of irradiation (exposure outside your body) and contamination (if it enters your body). It also needs extra safety precautions to be disposed of.
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Wind and solar energy
- Wind power involves putting lots of wind turbines up in a exposed place.
- Each wind turbine has its own generator inside it so the electricity is generated from the wind turning the blades.
- There is no pollution.
- They can be noisy and spoil the view.
- There is also no power when the wind stops, and it's impossible to increase the supply.
- The inital costs are quite high, but there is no fuel costs and minimal running costs.
- Solar cells generate energy directly from sunlight.
- There is no pollution, although they use quite a lot of energy to manufacture.
- Initial costs are high but after that the energy is free and there is a low running cost.
- Usually used to generate energy on a small scale (individual homes)
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Wave and tidal energy
- Lots of small wave-powered turbines located around the coast.
- As waves come into shore the up and down motion directly drives the turbine, and there is no pollution.
- They are fairly unreliable, since waves tend to die when the wind drops.
- Initial costs are high, but there are no fuel cost and minimal running costs.
- Tidal barrages are big dams built across river estuaries with turbines in them.
- As the tide comes in it fills up the estuary to a height of several metres, it also drives the turbines. This water can then be allowed through the turbine at a controlled speed.
- The source of energy is the gravity of the Sun and the Moon.
- There's no pollution. Tides are pretty reliable. However the height of the tide is variable so lower tides will provide significantly less energy than bigger tides.
- Initial costs are moderately high, but there is no fuel costs and minimal running costs.
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Biofuels, geothermal and hydroelectricity
- Biofuels are made from renewable energy sources (plants and waste).
- They are burnt to heat up water just like in thermal power stations.
- Relatively quick and 'natural' source of energy. They are carbon neutral.
- Geothermal is heat from underground and is only possible where hot rocks lie quite near to the surface. Water is pumped down pipes and returned as steam.
- However the cost of drilling down several km is quite high. And there is very few places this seems to be an economic option.
- Hydroelectricity usually requires flooding a valley by building a big dam. Rainwater is caught and allowed through turbines, driving them directly .
- There is no pollution but flooding the valley has a big impact of the environment.
- Initial costs are high but there is minimal running costs.
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Comparison of energy resources
- The UK uses a lot of electricity and the demand is increasing.
- Renewable sources struggle to produce the same sort of energy output as convential power stations.
- All our fossil fuels will probably run out in 50 years.
- Environmental impact needs to be considered as well as cost.
- Economics to consider; Running cost and setup cost.
- Environmental impacts; Waste and air pollution, noise pollution, carbon dioxide, visual pollution, resources, disturbing habitats, explosions.
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Generators and the National grid
- Moving a magnet in a coil of wire induces a voltage. This is electromagnetic induction.
- As you move the magnet, the magnetic field through the coil changes, this change in the magnetic field induces a voltage, and a current flows in the wire
- Generators use this to turn kinetic energy from turbines in powerstations into mains electricity.
- Magnet moving faster = Bigger voltage
- The bigger the voltage and current the more fuel we use up.
- The National grid is the network of pylons and cables that distributes electricity to the whole of Britain.
- It takes electrical energy from power stations to homes and industries.
- It's much cheaper and more efficent to distribute at a really high voltage, this keeps the current very low and reduces energy loss.
- The voltage is then reduced before it gets to our homes so it reaches us at 230 V, this is the mains supply voltage.
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