Evaluating fuel cells
fuel cellDevice that produces a voltage continuously when supplied with a fuel and oxygen. 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 fuelMaterial that is used to produce heat, like coal, oil or gas. 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 cellA device that converts light energy into electrical energy.. These convert light into electricityThe flow of charge through a conductor., so the hydrogen and oxygen can be replaced by the electrolysisThe decomposition (breakdown) of a compound using an electric current. 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.
| Fuel cell | Petrol or diesel | |
| Strengths | Quiet in use; only waste product is water; fewer moving parts | Petrol and diesel are easier to store; thousands of filling stations |
| Weaknesses | Hydrogen is more difficult to store; few filling stations | Noisy in use; carbon dioxide is a waste product; many moving parts |
| Strengths | |
|---|---|
| Fuel cell | Quiet in use; only waste product is water; fewer moving parts |
| Petrol or diesel | Petrol and diesel are easier to store; thousands of filling stations |
| Weaknesses | |
|---|---|
| Fuel cell | Hydrogen is more difficult to store; few filling stations |
| Petrol or diesel | Noisy in use; carbon dioxide is a waste product; many moving parts |
Hydrogen, diesel and petrol are all highly flammableAble to ignite and burn. 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.
Question
Suggest a reason that explains why the quietness of fuel cell vehicles may be a weakness.
Pedestrians may not hear the vehicle coming, and so they may be more likely to be run over when crossing the road.
Fuel cells and pollution
Hydrogen-oxygen fuel cells do not contribute directly to the greenhouse effect as they do not produce carbon dioxide, like other fuels, when they are in use. However, they do still cause pollutionContaminating the air, water or ground with harmful substances.. For example, the fuel cells use catalysts to make them work faster. These catalysts are toxic, and have to be disposed of when the fuel cell reaches the end of its useful life.
In addition, the hydrogen used to power the fuel cell is currently manufactured using fossil fuelNatural, finite fuel formed from the remains of living organisms, eg oil, coal and natural gas., such as coal or natural gas, as one of the raw materials. A by-product of this method of production is carbon dioxide, which contributes to the greenhouse effect. Although hydrogen can also be produced by the electrolysis of water, using renewableEnergy sources that are replenished and not exhausted, eg solar power. energy resources, such as wind or water power, the electricity needed is mostly still generated using fossil fuels.
Fuel cells may not directly release carbon dioxide into the atmosphere 鈥 but they are not 100% free from carbon dioxide production through indirect methods.