Energy resources

• Hydroelectric dams

  As water flows downhill (e.g. from mountains), a hydroelectric dam will trap the water in a man made lake, which is also known as a reservoir.

  Then whenever water is released through the dam, it spins turbines which are connected to generators, and so produce electricity.

  The water can then return to the river on the downstream side of the dam.
• Tidal barrages work in a similar way to hydroelectric dams. However, instead of damming water that's flowed down from upstream like a conventional dam, a tidal barrage allows water to flow into a bay or river during high tide, and then releases that water during low tide.
• Energy transfer in hydroelectric dams and tidal barrages

  In both cases the water on the higher side of the dam or barrage contains lots of gravitational potential energy. Once the dam or barrage is opened, this energy is transferred to kinetic energy as the water rushes down to the lower side.

  As the waters moves past turbines, some of its kinetic energy is transferred to the turbines, causing them to start spinning. Generators can then use this energy to generate electrical power.
• Which energy transfer takes place as water flows from the higher side of a hydroelectric dam (or tidal barrage) to the lower side?

  GPE -> KE
• What are the advantages of hydroelectric dams?


   Higher electricity demands can be met by increasing water flow 

  They are a source of renewable energy 
• What are the disadvantages of tidal barrages and hydroelectric dams?


  Upfront costs can be high and they can flood land upstream
• Wave power

  The water in the sea rises and falls because of waves on the surface. Wave machines use the kinetic energy in this movement to drive electricity generators.
• Advantages of wave power

  1.  It is a renewable energy resource and there are no fuel costs
  2. No harmful polluting gases are produced
• Disadvantages of wave power

  1. It is difficult to scale up the designs for wave machines to produce large amounts of electricity
  2. Having many wave machines can negatively affect wildlife 
• Biofuels:

  Biofuels are mostly made from recently living organisms, such as plants and algae. But they can also be formed from animal waste.

  This is in contrast to fossil fuels, which are made from organisms which died millions of years ago. 

  In both cases though, plants and algae can trap the suns energy as part of photosynthesis, and this energy is released when we combust the fuel. 
• What are the advantages of biofuels?


  they are renewable, easy to transport, and can be used in cars
• What are the disadvantages of biofuels?


  they require a large area to grow and require a lot of energy to harvest and produce
• In order to grow the biofuels, we often have to clear land by cutting down trees. This means the trees can no longer photosynthesise and absorb CO2 themselves, and will also release large amounts of CO2 if burned. 

  In addition, it usually requires a lot of energy to harvest, process, and transport the biofuels, which itself will produce a lot of CO2.
• Geothermal energy is the thermal energy generated and stored in the Earth. The geothermal energy of the Earth's crust originates from the original formation of the planet and the radioactive decay of materials like uranium deep in the Earth.
• Geothermal power stations provide a reliable source of electricity 
• 1. In regions with lots of volcanic activity, the ground is naturally very hot.
  2. So when we pump cold water down into the ground it will be heated by the hot rocks.
  3. If we pump this hot water back up to the surface we can use it to heat our homes.
  4. Alternatively, we let it heat up so much that it evaporates into steam.
  5. The steam can then be used to turn a turbine, which in turn can drive a generator to produce electricity. 
• Disadvantages of geothermal energy


  They can only be built in certain areas of the world  and can be expensive
• Advantages of geothermal


  Running them doesn't produce any pollutants and Installing them only does a small amount of damage to the environment 
• Wind power is generated by wind turbines which have blades that spin due to the wind. This spinning action turns a generator which produces electricit