Energy from the Sun (Cambridge O Level Physics)

• Most of our energy resources on the Earth come 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 forms of energy, 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

Solar Radiation

• The energy from the Sun that falls on the Earth is transferred by radiation 
  • This is 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 in 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 is expensive (due to the equipment required) and inefficient

Solar Cells

• Solar cells transfer energy from sunlight electrically producing a current, and 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

Field of Solar Cells

Solar cells use energy from sunlight to produce electricity

Solar Panels

• Solar panels transfer energy from sunlight to the thermal store of the solar panels
  • This can be used to heat water in pipes for domestic water supplies 
  • This can reduce the cost of producing hot water since it is heated partially by the solar panel

Function of a Solar Panel

Solar panels use energy from sunlight to heat water

Solar Furnaces

• Solar furnaces consist of large curved mirrors that focus the Sun's rays onto a small area
• These can be used to heat water to generate steam which can turn turbines and generate electricity in a power station
  • 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 (e.g. for a shower)

Advantages of Solar Energy

• Solar energy is a renewable resource
• In many places on Earth, sunlight is a reliable energy resource (i.e. places where the Sun shines most of the time)
• Solar farms produce no greenhouse gases or pollution
• Solar energy can be generated in remote places and in individual homes
• Solar panels are cheaper to produce and maintain than other energy sources

Disadvantages of Solar Energy

• Solar farms need to be large scale to produce large amounts of electricity and this requires vast areas of land
• People often don't like the appearance of large solar farms, this is known as visual pollution
• In many places on Earth, sunlight is not a reliable energy resource (i.e. places where there is a lot of cloud cover)