From the sun .... solar water splitting. Think of it this way .... how much energy does it take to power all the vehicles in the world compared to how much energy it takes to warm and sustain a sphere 25,000 miles in diameter 93 million miles away? The answer cannot be expressed in 'quads' if it is to be meaningful. The answer is 'a hell of a lot'. We have the sun ... we have the water (70% of the earth) ... we have only to learn how to take advantage of the obvious.
The eight year estimate for solar panels producing the energy required to produce them is a little optimistic. Most estimates I've seen is ten to fifteen years. Solar panels, for the first decade they're used, are not so much an energy source but rather a way to pay for ten years of electricity up front. They are simply not efficient enough or cheap enough to be a viable means for efficient hydrogen production from electrolysis.
how much energy does it take to power all the vehicles in the world compared to how much energy it takes to warm and sustain a sphere 25,000 miles in diameter 93 million miles away?
But that's not the point. Yes, a lot of energy come to the earth from the sun every day. But how is that energy going to be collected, stored and transported? The real issues with energy use are always issues of collection, storage, and transportation. Why do you think we use fossil oil and coal? Because the energy in the fossil fuels has already been collected by plants over billions of years and stored by them in an easy to transport form that we can go out and dig out of the ground.
we have only to learn how to take advantage of the obvious.
But the "obvious" comes with a plethora of not so obvious pitfalls and technical hurdles for us to overcome. If a solar powered hydrogen economy were really so obvious and simple, we'd be running one right now.