Exploring our energy options - the Sun is the origin for most of our energy sources. Humans have relied on fossil fuels in the past, but what will fuel our energy needs in the future?

This resource provides explanations of the key concepts encountered when exploring the future of fuels – the ‘basics’ that every student should understand.

Lifecycle analysis

A lifecycle analysis measures the environmental impacts of a product or process from ‘cradle to grave’. That is from the beginning when the raw materials are produced through manufacturing and processing to product and waste.

Energy from the Sun

With the exception of nuclear energy, the Sun is the source of all other energy on Earth. The water cycle and winds are driven by the Sun. Biofuels and fossil fuels are dependent on photosynthesis where plants harness the Sun’s energy to make sugars.

Conservation of energy

The law of conservation states that energy cannot be made or destroyed. This means that the amount of energy in a system is constant. It can be transformed from one form into another (for example, electrical energy to heat energy) but will never be destroyed.

Energy efficiency

When energy changes form (through transformation or transfer), there will always be some energy that is lost to the environment (such as heat). How well we are able to use energy is described as the efficiency. The more energy lost to the environment, the less efficient the energy transfer.

Renewable and non-renewable energy sources

Renewable energy comes from a source that we can either reuse (such as water) or replace (such as trees). Conversely, non-renewable energy comes from a source that cannot be reused or replaced (or not for millions of years). Uranium used in nuclear power and fossil fuels such as oil are both examples of non-renewable energy sources.

Fossil fuel

Fossil fuels (peat, coal, oil and natural gas) were formed from animals and plants that lived hundred of millions of years ago. When an animal or plant died, under the right conditions, its body was compressed to form fossil fuels. The energy present in the fossil was trapped, and humans now use this energy when they burn fossil fuels. Fossil fuels are non-renewable because it takes millions of years for the process to occur. We will one day run out of coal, oil and natural gas.


Bioenergy refers to heat, electricity or fuels produced through the conversion of biomass. Biomass is a natural replaceable resource. It refers to any organic materials that have been recently derived from plants (for example, wood, wood waste, manure, straw and other byproducts of agricultural processes). Bioenergy is an important form of renewable energy.


Carbon dioxide (CO2) is a gas that plays an important part in the carbon cycle. It makes up just 0.004% of the atmosphere, yet with the more abundant water vapour, it soaks up infrared radiation (heat) from the Earth’s surface and stops it from escaping into space.

CO2 emission

CO2 emission is the amount of carbon dioxide (CO2) released into the atmosphere.

Carbon cycle

Carbon is a chemical element vital to all living things and is also present in many non-living things. Carbon circulates around the planet in what is called the carbon cycle. It moves through the carbon cycle in stops and starts. An individual atom might pass through plants, animals and the atmosphere in a matter of days, yet stay trapped in rocks for millions of years.

Useful link

More about the solar energy budget.

    Published 10 June 2008