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Fuel cells have different strengths and weaknesses, depending on the intended use. For example, fuel cells are used in spacecraft and vehicles.

Fuel cells in spacecraft

Hydrogen-oxygen fuel cells are used in spacecraft. Their strengths include:

• they have no moving parts to maintain
• they are small for the amount of electricity they produce
• the water they produce is useful as drinking water

Hydrogen-oxygen fuel cells must be supplied with hydrogen fuel and oxygen. This could be a problem once a spacecraft leaves the Earth. However, spacecraft in orbit (such as the International Space Station) have solar cells. These convert light into electricity, so the hydrogen and oxygen can be replaced by the electrolysis of water. Solar cells only work when they are in the light, so the fuel cells allow electricity to be produced even when the spacecraft is in the dark.

Fuel cells in vehicles

Some cars and buses contain hydrogen-oxygen fuel cells. These power an electric motor, which turns the wheels. Other vehicles use engines fuelled by petrol or diesel. The table shows some strengths and weaknesses of each type of vehicle.

Hydrogen, diesel and petrol are all highly flammable fuels, but hydrogen is more difficult to store because it is a gas and the other fuels are liquids. As there are far fewer hydrogen filling stations, it may be more difficult to travel long distances in a fuel cell vehicle. However, fuel cell vehicles have fewer moving parts than vehicles fuelled by petrol or diesel, so they may be more reliable or easier to maintain.