The diagram illustrates and compares the two processes of generating electricity from brown and black coal, highlighting the amount of energy lost at each stage of electricity generation.
Firstly, as shown in the diagram, the initial fuel energy input is 100 units, which is the same for both types of coal. However, at the power station stage, brown coal loses 70 units, leaving 30 units. In contrast, black coal loses 68 units and retains 32 units, making it more efficient than brown coal.
Then, both of them lose 3 units during the transportation and distribution phase.
Ultimately, we observe that consumers receive 27 units of energy (or electricity) from the initial 100 units of brown coal, compared to 29 units from black coal.
In summary, it is evident that black coal is more efficient at generating electricity, primarily because it loses fewer units than brown coal in the power station phase.