>>you can’t just assume that we’ll never improve efficiency or access to energy after today.
Look at how you completely make up a strawmen position that does not represent what I said. I did not say that.
>> more efficient extraction of hydrogen from water
Do you understand that ANY “extraction” (the correct term is electrolysis, or other term, depening on method) of H2 from H20 involves a net LOSS of energy from the energy you put into the process? This is an example of the first law of thermodynamics, sometimes also called the law of conservation of energy. Do you understand it?
And here is some food for thought on solar: Current best-of-breed commercial solar technology has a conversion efficiency of 20%. Do you understand that it is physically impossible to have > 100% efficiency? Let me translate for you: We cannot improve more than 5x from where we currently are.
Not only is there no exponential improvement, there will soon be not accelerating improvement, but *decellerating* improvement in solar technology. That does not make it useless, far from it, but there is no silver bullet there. The limit of 100% efficiency is what I meant when I said “fundamental limitations” above.
Solar in space? With microwave links beaming cheap energy down to earth? People have been talking about that since 1950s if not earlier. You are dreaming, both cost-wise and efficiency-wise. Get real.
The first law of thermodynamics still holds in the 21st century. It is perhaps the most fundamental physical law there is. It will NEVER go away.
