Activity: Fuels
You might think of a flapjack or the wall socket as being your go-to source of energy, but ultimately all the energy stored in fuels originates from the Sun. Here you'll find out how to explain this and make use of Sankey diagrams to represent energy flow. Also in this activity, you will calculate the amount of energy release when different fuels are burnt and come to understand the principles of heat engines and generators.
Need to know
Fuels are chemicals that are burnt to produce heat energy which can be converted into mechanical energy by an engine or turbine which is used to turn a generator to produce electricity. The energy in most fuels originates from the Sun.
This can be represented on an energy flow diagram like the one below. Drag and drop the labels to their correct place.To convert heat into work requires some sort of engine. To understand the concept of a heat engine let us consider a hypothetical engine powered by a helium balloon.
- Where does the energy given to the car come from?
The car stops after a short while so to go further you would have to pull the balloon back down.
- Why is this engine pointless?
Now, imagine you used a hot air balloon instead of a helium balloon.
- How could you bring the balloon back down without doing any work?
- Where does the energy come from to power the car?
The balloon is heated by burning fuel > the balloon rises transferring energy to the car > the balloon cools and come down > the cycle repeats.
For the balloon engine to work heat must be lost, this is true for all heat engines (if you have done the engineering option you'll know this). This can also be represented on a Sankey diagram.
- Make a Sankey diagram for an engine using 10 kg of wood with an 80% efficient burner and a 60% efficient engine. Note the controls on the diagram are % heat loss not efficiency.
A power station produces electricity by burning fuel. The fuel could be coal oil or gas but the principle is the same.
Here is a video explaining the process: