2.12 producing electrical energy


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2.12 producing electrical energy

  1. 1. 2.12 Producing electrical energy – renewable sources 4 January 2011
  2. 2. Key terms <ul><li>Transformer – a device that changes the voltage of an alternating current without changing its frequency </li></ul>
  3. 5. Hydroelectric power <ul><li>Hydroelectric power stations are one example of the use of renewable energy sources </li></ul><ul><li>Water is stored behind a dam, often high up in the mountains </li></ul><ul><li>The height of the reservoir provides a source of potential energy </li></ul><ul><li>When the water is released and flows downhill, the PE is converted to kinetic energy and the energy turns the turbines </li></ul><ul><li>No burning of fuels so no pollution with nearly 90% efficiency </li></ul>
  4. 8. List the energy transformations that take place in a hydroelectric dam
  5. 11. Wind Power <ul><li>Wind turbines use the KE of the wind to turn the turbines to produce electricity </li></ul><ul><li>No pollution is produced but people worry that the wind turbines spoil the view of the countryside and the noise produced </li></ul><ul><li>Although wind is free, the turbines are expensive </li></ul><ul><li>No wind, no electricity </li></ul><ul><li>When they do operate the efficiency can be around 35-60% </li></ul>
  6. 16. Solar power <ul><li>Solar power can be harnessed using solar cells called photovoltaic cells . When the sun shines on these cells they emit electrons which form a current </li></ul><ul><li>The solar panels are expensive, but the energy source is free and no pollution is produced. </li></ul><ul><li>However, the amount of electricity generated depends on how bright the sunshine is </li></ul><ul><li>As with wind power, the efficiency of energy conversion varies, between 12-25 % </li></ul>
  7. 22. Compare the efficiencies of three renewable methods used to generate electricity and list their advantages and disadvantages
  8. 27. Getting electricity to our homes and factories <ul><li>The UK has a network grid of pylon towers linked by copper cables that transfer electrical energy to our homes </li></ul><ul><li>The voltage produced at the power station is about 25 000 V </li></ul><ul><li>Engineers than increase the voltage to 400 000 V using a step-up transformer </li></ul><ul><li>This reduces the energy losses during transfer, the higher the voltage the lower the current </li></ul><ul><li>A step-down transformer then reduces this to 230 V for your houses (or 11 000 V for some factories) </li></ul>
  9. 28. Assessment activity <ul><li>Explain why the voltage used in the home is different from that used to transmit electricity over the national grid </li></ul><ul><li>Which equipment is used to increase and decrease the voltage as electricity is transferred from the power station to our homes and factories </li></ul><ul><li>Which type of renewable energy power station would you recommend to be built near your community. </li></ul>