Page 166 - Science Coursebook

11.3 Renewables and non-renewables

About one-eighth of our energy comes from renewable
energy resources. These include wind and water power,
solar energy and biofuels.

A renewable energy resource is one which we cannot use up.
The energy we use today will be replaced naturally in the
future.

Wind power The three blades of the turbine are

The wind can turn a windmill. Nowadays, wind turbines turned by the wind. The generator is
are used to generate electricity. behind the turbine.

Water power
A river can turn a mill wheel. If the river is dammed, the
water can be used to turn turbines connected to generators –
this is hydroelectricity. Waves and tidal currents can also
be used to generate electricity.

Solar energy
The Sun’s rays can be used to heat water. They can also be
used to generate electricity using photovoltaic cells (solar cells). These are photovoltaic cells generating
electricity from sunlight.
Biofuels
Wood is a biofuel that many people around the world rely on.
Crops, such as maize and sugar cane, can be harvested and
fermented to produce liquid fuel for cars and trucks.

Questions
1 List the four ways of generating electricity mentioned above.
2 Draw energy arrow diagrams to show the energy changes that happen in a
solar cell and in a wind turbine.

Fossil fuels are described as non-renewable energy resources. This is because,
once they have been burnt, they are gone forever. Because they take millions of years
to form, we would have to wait a very long time for new fossil fuels to form to replace
the ones we use.

Solar energy is described as renewable. This is because, if we use the energy of
sunlight to heat water or to generate electricity today, there will be more
sunlight tomorrow.

Question

3 Explain why wind energy, used to turn a wind turbine, is a renewable
energy resource.

164 11 Energy

A+I A+E SE