Energy from the Sun (CIE IGCSE Physics)

EXTENDED

• 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

 

• 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 is expensive (due to the equipment required) and inefficient

• 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

Solar cells use energy from sunlight to produce electricity

Advantages

• Solar energy is a renewable resource
• In many places on Earth sunlight is a reliable energy resource (this means that the sun shines most of the time)
• Solar farms produce no greenhouse gases or pollution
• Solar energy can be generated in remote places where they don't have electricity
  • For example to power solar street signs in rural areas

    

Disadvantages

• Solar farms need to be large scale to produce large amounts of electricity
  • This is expensive to set up
  • 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 (there are not enough sunshine-hours to justify the set-up costs)

• 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 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)

Advantages

• Solar energy is a renewable resource
• In many places on Earth sunlight is a reliable energy resource (this means that the sun shines most of the time)
• Solar panels produce no greenhouse gases or pollution once they are operating
• Solar panels can cut the cost of energy bills for households

   

Disadvantages

• Solar furnaces need to be large scale to produce high temperatures
• Energy is still needed to heat water to a higher temperature in domestic households
• In many places on Earth sunlight is not a reliable energy resource (the sun doesn't shine regularly enough to justify the set-up costs)