Past exam of the short options paper shared by Prelims and Parts A and B of the physics course of the University of Oxford / 2016 / S4 / 3 / e / Solution

At fixed electrical output, improving efficiency from ${\eta }_0$ to ${\eta }_1$ reduces fuel and associated combustion emissions by $1-{\eta }_0/{\eta }_1$. A change from 0.33 to 0.45 saves about 27%. If an illustrative large coal fleet emits 3.6 Gt annually, that is nearly 1 Gt, exceeding a hypothetical 0.5 Gt national total and far exceeding a 0.1 Gt electricity-sector total. Thus the comparison can be true on reasonable scale assumptions. It is not established by the words “state of the art”: fleet sizes, existing efficiencies, feasible retrofit fractions and whether UK electricity or all UK energy is meant must be specified. Continued growth and rebound can offset technical savings, and the options are not mutually exclusive.