Given that one of the key factors in the climate change race is the speed that our global society will have to transform, existing infrastructure presents a potentially useful opportunity - potentially saving on cost and the time to deployment.
Existing infrastructure might be reusable in the following ways…
Extraction - could old empty fossil fuel reservoirs be used to store new “green” fuels? In the case old deep mines, they can be used to store energy using the pumped hydro-electric process.
Processing - this might be reusable to an extent, and depends on the chemistry.
Storage - potentially useful to address the need for seasonal storage of green energy/fuel (e.g. supplying energy when the sun doesn’t shine much in winter, and the wind doesn’t blow).
Transport of fossil fuels - potentially useful for shifting energy (fuel) around the to where (and when) it’s needed.
This is dependent on the clean fuels used (e.g. hydrogen, methane).
Some context for this can be seen in the Global Renewable Energy Network diagram.
PS: The barriers would become clearer during the challenge.