Living for the Future

Solar Energy
1. Photocells
  1. Robust, little maintainance
  2. Solar fuel, no long cables
  3. No pollituon
  4. P-N silicon junction
    1. P-type has absence of free electrons
    2. N-type has excess free electrons
    3. Photons excite electrons
      1. Electric current produced
  5. (-) No energy when dark/cloudy
  6. Output:
    1. Light intensity
    2. Surface area
    3. Distance from light source
  7. DRAW OUT
2. Passive heating
  1. Glass lets in shorter IR radiation
    1. IR absorbed by walls and floor, heat up
      1. IR re-emitted at longer wavelength
        Glass reflects longer wavelength IR inside
3. Wind energy
  1. Windspeed dependent
    1. Will not work in too little/too much wind
  2. No CO2
  3. Noisy. take space, "NIMBY"
Generating Electricity
1. The Dynamo effect
  1. Wire coil in a magnetic field = Current
    1. Induced current
  2. Increasing the effect:
    1. Faster moving magnet
    2. More wire coils
    3. Stronger magnet
  3. To reverse current:
    1. Rotate magnet in opp. direction
    2. Reverse magnet polarity
  4. Either the coil OR the magnets can move
  5. Always AC
  6. DRAW OUT
2. Power Stations
  1. Water boils to steam
    1. High-pressure steam drives turbine
      1. Turbine drives Generator
3. Energy Efficiency
  1. Energy lost at each stage
  2. Efficiency = Useful output / Total input
Global Warming
1. Most electromagnetic waves pass through atmosphere
  1. IR absorbed at short wavelengths by Earth
    1. Re-emitted at long wavelengths
      1. Long wavelengths trapped
        CO2
        Volcanic eruptions
        Forest fires
        Organic decay
        Oceans emit it
        Respiration
2. Greenhouse Gases
  1. Methane
    1. Decay lacking oxygen
    2. Wetlands, oceans
  2. CO2
  3. Water vapour = Most potent
    1. Occurs naturally
3. Dust : Two effects
  1. Factory smoke traps IR
    1. Temp. Increases
  2. Volcanic ash reflects IR
    1. Temp. falls
Fuels for Power
1. Measuring power
  1. Appliances use a certain amount of power per second
  2. Power = Voltage x Current
    1. Watts
  3. Energy supplied = Power x Time
    1. Kilowatt Hours (kWh)
2. Cost of Energy
  1. Cost = Energy used x Cost per kWh
  2. Often lower rates at night (off-peak)
3. Choices of Sources
  1. Availability
  2. Ease of extraction
  3. Environmental effect
  4. Risks associated
4. The National Grid
  1. Transformers step up VOLTAGE to 400,000v
    1. Transport electricity in powerlines
      1. Transformers step down energy for consumer
  2. High current heats up wires
    1. Heat = Energy loss
      1. Transformers allow higher [Voltage] and lower [Ampage]
        Lowers energy lost
        Keeps cost down
        "When a transformer increases voltage, the ampage is reduced - Wires don't heat up, and therefore less energy is lost to the environment (sink)."
5. PRACTICE EQUATIONS

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Living for the Future

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	Criado por Oliver Wood quase 11 anos atrás