Energy

• Power: 


  the rate at which energy is transferred or rate at which work is done, per second in watts.
• Conservation of energy:


  Energy cannot be created or destroyed
• In all systems energy is dissipated, so that it is stored in less useful ways, known as 'wasted'
• Reducing energy waste:


  Lubrication

  • Oil in a motor
  • reduces friction
  • so less energy is lost (heat) through friction

  Thermal Insulation

  double glazing

  less useful thermal energy lost
• The higher the thermal conductivity of a material, heat is allowed to travel through the material more easily, so the higher the rate of energy transfer by conduction across the material.
• Thermal conductivity in a building:

  • rate of cooling is low if walls are thick and thermal conductivity of the walls are low
  • If the walls were thin metal sheets, heat would be lost very quickly
• the efficiency of a system can be increased by:

  • reducing waste output (lubrication, thermal insulation)
  • recycling waste output (absorbing thermal waste & recycling as input energy)
• non-renewable energy sources:

  • fossil fuels(coal, oil, gas)
  • nuclear fuel
• renewable energy sources:

  • biofuel
  • wind
  • hydro-electricity
  • geothermal
  • tidal
  • solar
  • water waves
• renewable energy is energy which can be replenished as it is used(wind will never stop), important due to the finite lifetime of fossil fuels.
• negatives of renewable energy: expensive to install and maintain, can be unreliable (solar doesn't work at night, wind is only intermittent)
• Non-renewable energy sources are used more for large-scale supplies, due to the large energy output per kilogram of fuel, but they are finite and will eventually run out.
• Main energy uses:

  • Transport
  • Electricity generation
  • Heating