Most of the energy that we use in the home is in the form of electricity. This electricity comes from power stations like the one shown below.
|Power station cooling towers|
How does a power station work?
You need to know the main parts of a power station and the energy transfers involved. Power stations generate electricity by using a fuel to generate heat, which boils water and produces steam. The steam is then used to turn large turbines. The kinetic energy of the turbine is converted into electrical energy by a generator. This process is shown in the following diagram:
In the diagram shown above, the fuel used is coal. Coal is a fossil fuel and stores its energy as chemical energy.
Fossil fuels were formed from dead plants and animals kept under pressure for millions of years. Coal, oil and natural gas are all fossil fuels.
Alternatives to fossil fuels
Fossil fuels are finite energy sources, meaning that they are non-renewable and cannot be replaced. They also produce polluting gases such as carbon dioxide when they burn, which contributes to global warming.
Scientists are currently working on finding and developing alternative sources of energy including renewable fuels. The main alternatives to fossil fuels are as follows. You need to be able to recall how each type of power station works, as well as knowing their various advantages and disadvantages.
Wind Energy - This consists of a turbine attached to a generator which converts kinetic energy to electrical energy. It is the same method of generating electricity in a power station, except the kinetic energy comes directly from the wind blowing, rather than steam from burning a fuel to boil water. Wind turbines don't pollute the atmosphere but have a few disadvantages. They do create noise pollution, can only operate at specific wind speeds, and some people are of the opinion that they ruin the look of the landscape.
Solar Energy - Solar panels convert sunlight directly into electricity. The energy transfer is therefore light to electrical energy. They do rely on sunlight (it's not always sunny!) and have to be very large to generate a lot of electricity. They do, however, have the advantages of requiring no fuel to operate and producing no pollution.
Hydroelectricity - This is another power station that converts the kinetic energy of a turbine into electrical energy as it spins a generator. This time, it's water that spins the turbine. Hydroelectric power stations store water from rivers or dams at great heights (storing gravitational potential energy) and then the water is made to flow downhill to turn the turbines. This creates no pollution, and the energy output can be controlled easily, but they can damage the landscape and it is very expensive to set up.
Nuclear - This is very similar to a fossil fuel station, as water is boiled into steam, which is forced through turbines to turn a generator. The only difference is that the fuel in a nuclear power station is not burned. Instead, nuclear fuel is placed in a reactor, has neutrons fired at it, and a process called nuclear fission occurs, where the nuclei split. This releases huge amounts of thermal energy, which is able to boil the water. Nuclear power produces a lot of energy from a very small amount of fuel but also creates radioactive nuclear waste and can be dangerous if rigorous safety standards are not met. The danger of nuclear energy was clearly demonstrated by the Chernobyl nuclear disaster in 1986 and the Fukushima disaster in 2011. Nuclear energy will outlast the fossil fuels of coal, oil, and gas, but it is not considered to be renewable.
Let's now think about energy in a different context: the energy in your food.
Food stores its energy as chemical energy. Once you have consumed it, your body will use this energy to transfer it to other forms so that you can move, breathe, and so on.
You may have seen nutrition information on food packaging. This isn't just there for people to read if they happen to be interested - it is a legal requirement for food companies to put this information on their packaging. People should consume a specific amount of energy every day, so they must be aware of how much energy is in their food (as well as sugar, fat, and so on), so that they can decide how much to eat, and to work out what foods will provide a healthy, balanced diet.
Finally, let's think about paying for energy.
Every home in the country needs to pay their energy bills to keep their lights switched on and all their appliances working. Energy companies will charge people by the kilowatt-hour (kWh) and work out their energy bill based on how many kWh a household has used. The kilowatt-hour is the amount of energy transferred by 1,000 W of power in 1 hour. Energy companies use this unit instead of the Joule, because the amount of energy in Joules would be such an incredibly large number, it would not make much sense.