The thing about these types of speculative calculations is they do not account for improvements in design.
They merely take existing data and produce a figure we ought to be anxious over.
Even if the figures are somehow accurate and translate into 50 to 100 yrs of energy production, just factor in the innovation aspect which is exploding exponentially with our population increase and related factors.
What is going on these days is amazing.
Now if we could tweak commerce a bit to unleash the dynamo………..
what a world we would see.
