Energy from Fuels

Fuels store chemical energy. When a fuel burns (combusts), this energy is released as heat. We use this heat to cook food, power vehicles, and generate electrical energy in power stations.

Types of Fuels

• Fossil fuels: coal, oil, natural gas. Formed over millions of years from dead plants and animals. They are non-renewable.
• Biofuels: fuels made from recent plant or animal material (e.g. wood, biogas, ethanol). They are renewable if new plants are grown to replace what is used.

From Fuel to Electricity

Many power stations using fuels follow this chain:

• Boiler: burning fuel heats water to make high-pressure steam.
• Turbine: fast steam spins turbine blades (kinetic energy).
• Generator: the spinning turbine turns a generator to produce electrical energy.

Energy transfers: chemical → thermal (steam) → kinetic (turbine) → electrical (generator). Some energy is always lost to the surroundings as heat and sound.

Why Fuels Are Useful

• High energy density: a small mass of fuel releases a lot of energy, which is helpful for transport and large-scale power.
• Reliable: fuel can be stored and burned when needed, giving steady electricity.

Advantages and Disadvantages

Fossil fuels

• Pros: very available today; high, steady power; easy to transport and store.
• Cons: non-renewable; releases carbon dioxide (greenhouse gas) and air pollutants; mining and spills damage environments.

Biofuels

• Pros: renewable if plants regrow; can be used in engines and power stations; can reduce waste (e.g. biogas from rubbish or manure).
• Cons: lower energy density than fossil fuels; large land use may affect food supply and habitats; not carbon-neutral if forests are cleared or farming uses lots of energy.

Efficiency of Energy from Fuels

Efficiency tells us how much of the input becomes useful output. $\text{Efficiency} = \frac{\text{useful energy (or power) output}}{\text{total energy (or power) input}} \times 100\%$.

Common Misconceptions

• Biofuels are not automatically “zero carbon”; the overall effect depends on how they are grown and processed.
• Hydrogen can be a fuel, but it must be produced using another energy source.