Energy resources

The main energy resources available for use on Earth include: fossil fuels (coal, oil and gas), nuclear fuel, bio-fuel, wind, hydro-electricity, geothermal, the tides, the Sun and water waves.

A renewable energy resource is one that is being, or can be, replenished as it is used.

The uses of energy resources include transport, electricity generation and heating.

You should be able to describe the main energy sources available, and distinguish between energy resources that are renewable and energy resources that are non-renewable. Descriptions of how energy resources are used to generate electricity are not required — so you do not need to explain the inside of a power station.

Nuclear fuel is non-renewable. It is not a fossil fuel and it releases no carbon dioxide when used, but the uranium is mined and is not replenished as it is used, so it fails the definition of renewable. That combination — non-renewable but not carbon-emitting — is why it is so often the subject of these questions.

Bio-fuel is renewable because the crops it is made from can be regrown as fast as they are burned.

You should be able to compare ways that different energy resources are used — the uses to include transport, electricity generation and heating — and to understand why some energy resources are more reliable than others.

Reliable means available whenever it is needed. Fossil fuels, nuclear fuel and bio-fuel are reliable because the fuel can be stored and burned on demand. Wind and solar are unreliable because they depend on the weather and, for solar, on the time of day. Tidal is unusual: it varies, but it varies predictably, so it can be planned for even though it cannot be switched on at will.

You should also be able to describe the environmental impact arising from the use of different energy resources, and explain patterns and trends in the use of energy resources.

The trend to be able to describe: use of fossil fuels is falling and use of renewables is rising. The reasons are that the environmental impact of fossil fuels is now well understood, governments have set targets to reduce carbon dioxide emissions, and renewable technology has become far cheaper. The reasons the change is slow are that renewables are less reliable, building new capacity is expensive, and much existing equipment — cars, boilers, power stations — was built for fossil fuels.

You should be able to consider the environmental issues that may arise from the use of different energy resources, and to show that science has the ability to identify environmental issues arising from the use of energy resources but not always the power to deal with the issues, because of political, social, ethical or economic considerations.

That distinction is the point of this part of the sub-topic, and it is examined directly. Science can measure how much carbon dioxide a power station releases, show what it does to the climate, and work out what the alternatives would cost. What science cannot do is decide whether a country should accept higher bills, whether a valley should be flooded for a reservoir, or who should bear the cost of change. Those are political, social, ethical and economic questions.