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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

Photovoltaic panels (DOE/NREL - Robb Williamson)
Solar energy is free, renewable and silent
Solar power

Solar power is often used to power calculators and other electronic accessories. Solar panels – made up of photovoltaic cells – are also sometimes used on roofs to provide electricity to households

Pros

  • Solar energy is free and renewable, generates no emissions and is silent
  • The cost of photovoltaic cells has dropped significantly in the past few years and is predicted to fall further as mass production increases
  • Photovoltaics are one of the few renewable technologies that can be integrated into the urban landscape
  • They are useful in remote areas far from a source of conventional electricity
  • Unused electricity can be fed back into a country’s national grid.

    Cons

  • Solar energy is of limited use in cloudy places and also in some cities where roof space is tight
  • PV cells are not very efficient, absorbing only about 15% of the sunlight’s energy
  • There are extra costs, such as systems to store the energy for when the sun is not shining
  • Some of the huge batteries used contain heavy metals, so pose an environmental risk if not properly disposed of
  • Toxic chemicals are also used in the production of semiconductors.

    How it works

    The properties of materials called semiconductors mean they can be arranged in a way which causes an electrical current to flow when light is shone on them.

    In a photovoltaic cell, two different types of semiconductor are layered together. Typically, the atoms on one side (n-type) have a single electron in the outer shell. The atoms on the other (p-type) are one electron short of a full outer shell. When the two layers are placed together, electrons move from the n-type side to fill the “holes” on the p-type side. This creates an electrical field at the junction between the two layers.

    Once set up, this electrical field effectively creates a barrier to more electrons trying to move from the p-type side to the n-type side. When light shines on the whole cell, it knocks electrons free from their atoms. But the charge at the junction causes all the free electrons to build up in the n-type layer.

    If an external electrical circuit then bypasses the junction, the electrons flow through it as a current.

    Engineers are now working on ways to develop large-scale solar plants to produce hundreds of megawatts at a time.

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