We take a lot of high concentration energy in fossil fuels and exploit it to give it a value, the exploitation of energy is traded using a fiat currency, the value is increased again when workers and consumers are added into the chain, this is done by printing money as more of it is created. Something that starts off as the release of energy ends up becoming trade of goods and services, each link in the chain adding more and more value and distributing wealth through the population. Capitalism isn't perfect but it works and is the best way to run a society that we know of so far.
The problem is Capitalism is brittle. If fossil fuels run out then money will die. We have to replace fossil fuels with natural energy like solar panels and wind. If consumers are replaced by robots then there are no consumers so we can't sell goods and services properly. I think that capitalism as we know it now won't work in a world were machines do all the jobs because machines don't spend money and they don't want anything.
Natural energy is hard to control because it comes in spurts, sometimes we get too much of it, other times there isn't enough. We need a way to spread the load so the supply is smooth a steady, I wonder how?
