1 Renewable and non-renewable energy

1.1 Renewable energy

Renewable energy is energy from natural resources or energy that can be replenished as quickly as it is used. When we think of renewable energy we usually think of solar panels on house roofs or wind turbines marching across the hills. Both make use of naturally occurring forms of energy, namely the energy in sunlight and the energy in the wind. The latter can be thought of as an indirect form of solar energy, as the differential heating of the Earth’s surface. Similarly, the wind passing over the sea creates waves and harnessing these provides another form of renewable energy, again an indirect result of sunlight.

We consider hydro-electric schemes to be renewable as well. Rain on high ground is collected in reservoirs and can be tapped to turn water turbines at a lower level to generate electricity. The climate system is generated by the sun, so again hydro power is an indirect form of solar energy. Tidal energy, by contrast, is the result of the gravitational pull of the moon and, to a lesser extent, the sun on the seas.

The other key renewable is often referred to as biomass. By this we mean plants that can be burnt to create heat but which can be replenished at the same rate as they are consumed. Sunlight, of course, provides the energy input to the plants to enable them to grow. Biomass plants are thus stored solar energy. In certain parts of the world we make use of geothermal energy, the heat within the Earth.