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Energy

Alternatives to oil

Could we live without fossil fuels which currently provide 90% of the world’s energy? Click on the bar below to explore the options.
Nuclear Hydropower Hydrogen Wind Solar Others

Flowing water
Hydropower provides nearly 10% of the world's electricity
Hydropower

Hydropower harnesses the energy from flowing water.

Pros

  • Hydropower is non-polluting.
  • It is renewable - water flows are replenished by the hydrologic cycle which is powered by the Sun.

    Cons

  • Hydropower only makes sense for countries with suitable climates and topographies
  • Building dams can involve diverting rivers, flooding farmland and countryside and displacing local people
  • Wildlife habitats are disrupted and fish can die in the blades of the turbines
  • Forests are often cut down to build the accompanying infrastructure
  • Dams can trap silt which would otherwise enrich soils downstream
  • Flooding is a potential hazard if the dam bursts or the reservoir fills with silt
  • Damming cross-border rivers can result in disputes with neighbouring countries downstream

    How it works

    Water stored behind a dam is released downhill through a pipe, turning a turbine as it flows. Most water turbines look similar to ships' propellers, with several blades set at an angle which can be adjusted depending on the output power required. The rotating shaft drives a huge electric generator, which transforms the mechanical energy to electrical energy.

    If the volume of water flowing into a dam is not sufficient to generate power continually, a pumped storage system can be used. Water which has passed through the turbine is stored in a lower reservoir and pumped back up to the upper reservoir using cheap, off-peak electricity. This water can then be reused to generate power when demand is high.

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