Well first of all, we're really talking about ambient energy since nuclear is just as renewable as anything powered by the Sun. The Uranium and Thorium our planet inherited from supernovas during its formation is only going to disappear through radioactive decay. And that won't be for many billions of years.
Second of all, nuclear power became profitable within a decade of its invention. Meanwhile, it's been more than 140 years since photovoltaics have been invented, and more than four decades since NASA has been funding their R&D, and what do we have? Bupkis. What does that tell you?
People seem to think that engineering can do anything, achieve anything. That it's just a question of waving your magic fairy wand and pouring enough money into it. Well it's not. And it's really very, very simple why it isn't. It goes like this:
- solar power is a DIFFUSE form of power
- this means that you need a MACHINE to concentrate solar power
- in our physical universe, a machine must be made of MATTER
- matter COSTS MONEY
Add it all up and what do you get? Solar power will always be more expensive than nuclear power. Always. Now and for all time.
The only reason hydro doesn't suffer the same fate is because we can use pre-existing mountains and ravines as the collectors. Once dam-builders have to pay for mountains, and this will happen when we start dismantling the Earth for a Dyson sphere, then hydro power will no longer be profitable.
Ambient forms of energy are inherently inferior and no amount of chanting by arch-druids and channeling the power of Gaia is going to change physics.