Band 8 model answer

It is frequently claimed that renewable sources will entirely supplant fossil fuels within the span of a single generation. While I am firmly convinced that renewables will come to dominate the global energy mix, I do not accept that so total a replacement is realistic within roughly thirty years.

There are powerful grounds for expecting renewables to surge. The cost of solar and wind generation has plummeted to the point where it now undercuts coal and gas across many markets, and mounting public alarm over climate change is prompting governments to subsidise clean power and to commit to ambitious decarbonisation targets. As battery storage and smart grids mature, the long-standing obstacle of intermittency, the awkward fact that the sun does not always shine nor the wind always blow, is being steadily overcome. In all probability, renewables will furnish the majority of the world's electricity well before the middle of the century.

Nevertheless, to speak of "completely" replacing fossil fuels within a generation overstates the case substantially. Several sectors, among them aviation, shipping, steel and cement, remain stubbornly difficult to electrify and will lean on hydrocarbons for decades yet. Much of the developing world, meanwhile, is still expanding its coal and gas capacity to satisfy soaring demand, and the sheer scale of the existing fossil-fuel infrastructure cannot conceivably be dismantled overnight. A transformation of this magnitude is the work of fifty years or more, not twenty.

In conclusion, although renewable energy is advancing at a remarkable pace and will undoubtedly become the dominant source of power, the assertion that it will wholly eliminate fossil fuels within a single generation strikes me as decidedly too optimistic.