Energy from the Sun (Cambridge International IGCSE Science)

The Sun

Extended Tier Only

• The Sun transfers energy to Earth by electromagnetic radiation

• Most of our energy resources on Earth come indirectly from the Sun:

  • The Sun heats up the atmosphere, creating wind and producing waves
  • Water evaporated by the Sun falls as rain, filling up reservoirs
  • Plants grown using sunlight form the basis for fuels – both biofuels and fossil fuels

• Some energy resources, however, do not come from the Sun

• These include:

  • Geothermal– this comes from heat produced in the Earth’s core
  • Nuclear– this comes from elements which make up a small proportion of the Earth’s crust
  • Tidal– this comes (mainly) from the gravitational attraction of the Moon

The Sun

Energy from the Sun is the source of the energy stored in many of Earth's energy resources

Solar cells

• The energy from the Sun that falls on the Earth is transferred by radiation

  • Mostly visible light and infrared radiation

• The amount of energy transferred from the Sun to the Earth each hour is equal to the energy use of the world for one year!

• Therefore, scientists are working hard to find methods of harnessing this energy

  • Solar energy has a low energy density, which means large collecting devices are required
  • Collecting solar energy has been expensive (due to the equipment required) and inefficient
  • Although improved technology has improved efficiency, greater demand has lowered costs

• Solar cells transfer energy from sunlight and produce a current, therefore generating electricity

  • Solar cells, sometimes called photovoltaic cells, are made of semiconducting materials
  • A number of cells connected together can supply electricity to homes, small-scale businesses, communication devices and satellites
  • Energy generated from solar cells can be stored in batteries for later use

Solar cells

Solar cells use energy from sunlight to produce electricity

Solar panels

• Useful energy may be obtained from infrared and other electromagnetic waves from the Sun using solar panels

• Solar panels transfer energy from sunlight to the thermal store of the solar panels which is used to heat water in the pipes

  • Solar panels can be used to warm domestic water supplies

    • This can reduce the cost of producing hot water since it is heated partially by the solar panels

  • Solar furnaces consist of large curved mirrors that focus the sun's rays on to a small area

    • These can be used to boil water, generating enough steam to turn turbines and generate electricity in a power station

Solar panel

Solar panels use energy from sunlight to heat water

• Water is stored in a water **tank **and pumped through small **pipes **running through the solar panel
• Infrared radiation from the Sun heats the water in the pipes as it flows through them
• The water returns to the tank at a** higher temperature**
• Water may still need to be heated further to reach the desired temperature (eg. for a shower)

Wind turbines

• Energy from the wind can be used to generate electricity

• The wind turns a turbine, which turns a generator, which generates electricity

• Energy from the kinetic store of the wind is transferred

  • mechanically to the kinetic store of the turbine
  • which is transferred mechanically to the kinetic store of the generator
  • which is transferred electrically to the National Grid

Wind turbines

Wind turbines use energy from the wind to generate electricity