C1aL15  Fuels of the Future

Key Words

Carbon dioxide - (CO₂)Waste product of burning fuels, a strong greenhouse gas.

Carbon monoxide - (CO)

Diesel - A fuel for cars with a diesel (compression ignition) engine.

Finite - Will last for a while, but no more.

Nitrogen oxides - compounds formed by the reaction between nitrogen and oxygen.  Cause pollution.

Petrol - a fuel used by petrol (spark ignition) engines in cars.

Pollution - waste material that fouls the atmosphere.

Unburned hydrocarbons  - fuel that has not been fully burned.

Water vapour - water in gaseous form.

Grade E

Cars and lorries are an important part of our lives and economy.  They are fuelled with hydrocarbon fuels, which consist of carbon and hydrogen.  There are two main kinds:

• Diesel, used by vehicles with compression ignition engines;
• Petrol, used by vehicles with spark ignition engines;

These engines cause pollution that makes the air unpleasant to breathe and other environmental problems.  The pollutants are:

• Carbon dioxide and water vapour (both greenhouse gases)
• Unburned hydrocarbons (fuel that has not been burned);
• Carbon monoxide (very poisonous);
• Nitrogen oxides.

Petrol and diesel are fossil fuels.  The supplies are finite, and will run out one day.

Grade C

Pollution can cause health problems as well as environmental damage, especially in cities.  Filthy air can bring on asthma attacks.

To reduce pollution, cars are now fitted with catalytic converters which change:

• carbon monoxide to carbon dioxide;
• unburned hydrocarbons to carbon dioxide and water;
• nitrogen oxides to nitrogen.

Catalytic converters only work when hot.   Some additives to petrol can coat the catalysts with material, stopping them from working.  This means an expensive repair, as the catalysts are rare metals.

Alcohols like methanol and ethanol are used as an additive to petrol.  However they release less energy per litre, so engines use more fuel.

Hydrogen is another fuel, usually used in fuel cells that make electricity.  However it has to be manufactured (by the electrolysis of water), which takes a lot of energy.  Also, hydrogen is highly flammable.  A pressurised cylinder could go off like a bomb in the case of an accident.

Grade A

Electric vehicles use a lot less fuel.  Far from being modern, electric vehicles have been around as long as petrol vehicles, about 120 years.  They cause no pollution.  However they need heavy batteries to power them and they tend to be rather slow.  Their range is limited to about 100 - 200 km, not very useful.

Nobody has yet cracked the problem of making a battery that weighs no more than a fuel tank.