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Energy transfer and storage

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Renewable resources

Renewable energy resources can be replaced, and will not run out. Be careful - it is not true to say that they can be re-used.

Biomass

Biomass fuels come from living things. Wood is a biomass fuel. As long as we continue to plant new trees to replace those cut down, we will always have wood to burn. Just as with the fossil fuels, the energy stored in biomass fuels came originally from the Sun.

Wind power

A wind turbine - the nacelle turns the blades using a generator. The nacelle and the blades are held up by the tower, and the tower is supported by foundations

Wind is caused by huge convection currents in the Earth's atmosphere, driven by heat energy from the Sun. The moving air has huge amounts of kinetic energy, and this can be transferred into electrical energy using wind turbines. Wind turbines cannot work if there is no wind, or if the wind speed is so high it would damage them.

Water power

Moving water has kinetic energy. This can be transferred into useful energy in different ways. For example:

  • wave machines use the up and down movement of waves to turn electricity generators

  • tidal barrages are built across the mouths of rivers. As water moves in or out of the river mouth when the tide turns, the kinetic energy in the water is used to turn electricity generators.

  • Hydroelectric power (HEP) schemes store water high up in dams. The water has gravitational potential energy which is released when it falls. As the water rushes down through pipes, this stored energy is transferred to kinetic energy, which turns electricity generators.

An energy transfer diagram for an HEP scheme:

Water behind a dam (store of gravitational potential energy). Energy is transferred as kinetic energy to water flowing in pipes. Energy is transferred as kinetic energy to a generator. Energy is transferred as electrical energy to power lines.

Geothermal

In some places the rocks underground are hot. Deep wells can be drilled and cold water pumped down. The water runs through fractures in the rocks and is heated up. It returns to the surface as hot water and steam, where its energy can be used to drive turbines and electricity generators

Solar cells

Solar cells are devices that convert light energy directly into electrical energy. You may have seen small solar cells on calculators. Larger arrays of solar cells are used to power road signs, and even larger arrays are used to power satellites in orbit around Earth.

Solar panels

Solar panels are different to solar cells. Solar panels do not generate electricity. Instead they heat up water directly. A pump pushes cold water from a storage tank through pipes in the solar panel. The water is heated by heat energy from the Sun and returns to the tank. They are often located on the roofs of buildings where they can receive the most sunlight.

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