[kragen]

nuclear energy is very exciting and absolutely crucial for space exploration, but not economically competitive with solar in the foreseeable future on earth's surface

there are also solar panels still producing power after 50 years; they do degrade a little, especially in the first ten years, but the 20–30 year panel lifetimes you see published are more of a warranty and accounting issue than anything else. (of course some panels crack or yellow within a year or two)

it's true that solar farms take up a lot of space, but even in high-density countries like japan there is room for them. singapore might have a problem tho

[wait_a_minute]

What would surface area needs be like for over-provisioning needs in the US? What if we want to scale energy production by 2x or 10x or 100x for advanced industrial and commercial usage needs in the future? I think then the solar panel approach becomes limited on earth.

You’re right that the panels don’t degrade a ton. I read online that after 20-30 years they might drop 15% efficiency. For residential usage that might be okay, but it does mean needing upkeep and worrying about baseline potential dropping, which in some climates could be bad.

I do think a combination of the technologies is best, since scaling up energy production will be simpler and easier and more resource-friendly with nuclear than with more solar. Moving up the Kardashev scale will require capturing all the energy that can be captured from all sources so why let any go to waste. :)

[imtringued]

If you want to scale to 100x power you're going to have to rely on solar power even more than we already do. You seem to be awfully attached to the idea that the reactor must be located on earth. Solar power is fusion power with the reactor being located in space. It is very unlikely that humanity can build a bigger reactor.

[kragen]

humanity, defined loosely, can definitely build a bigger reactor than the sun. the milky way is a trillion times bigger than the sun, and mostly made up of stars (as opposed to large black holes, which are probably effectively inaccessible), so there's plenty of material available

already-existing natural blue hypergiants can reach energy outputs several million times that of the sun, in large part because they're on the order of 100 times bigger, usually limited only by the eddington mass limit. bat99-98 is estimated at 226 solar masses. so designed artificial stars can clearly reach that size, and conceivably, with a better understanding of plasma dynamics, they could be stabilized. in fact, we already know† how to build an even larger star: if you build a star of very low metallicity (similar to natural population-iii stars, of which possibly none survive today), its eddington mass limit is much higher, around 1000 solar masses

more likely, though, the humans will instead build a larger number of smaller, safer reactors. microscopic black holes can convert mass into hawking radiation at manageable photon energies and useful power levels. the necessary experimentation poses no risk of creating a large black hole (the density of matter necessary to grow small black holes to macroscopic proportion doesn't exist outside of the cores of stars, and the necessary quantity of matter at those densities is also literally astronomical) but will surely involve many explosions as starving black holes explode in a final tantrum of high-energy gamma rays, and of course must be carried out in free fall to prevent your nascent black hole from simply falling between the atoms of your laboratory floor before exploding deep inside your chosen planet

constructing larger reactors, by contrast, does pose a risk of producing phenomena such as disappointing white dwarfs, neutron stars, and black holes, or worse, supernovae, rather than a useful power source

if we believe dyson's calculations, though, a much more worthwhile thing to do is to figure out how to slow down our entropy production enough to preserve life into the cold, dark post-stellar era

______

† i mean we know in scientific terms what the structure of such an artificial star would be, where to find the materials, and what would be required to bring them together in the right way. it's fairly simple, actually. the only difficult part is getting a large enough budget to build the necessary fleet of spacecraft to harvest 10³³ kg of hydrogen and helium, about a billionth of the milky way, and bring it together over a distance of several light years; plausibly you need on the order of 10³⁵ spacecraft, about 120 doublings of a von neumann probe

[kragen]

yes, as you approach kardashev type 1 you will definitely want to start harvesting sunlight from von neumann probes on solar orbit

including transportation, natural gas, etc., but not including foods like corn and canola, the usa uses 100 quads per year, or 3.3 terawatts in si units. its average utility-scale solar power capacity factor is 21%, so you'd need 15.7 terawatts peak of solar farms to supply that, before scaling up by 2× or 10× or 100×. 15.7 terawatts of 24% efficient solar panels would require 65 terawatts of sunlight, which is to say, 65 billion square meters or 65536 square kilometers (to pick a round number). this is of course 256², so, like the entire spectrum of mainstream political opinion in the usa, it would all fit between houston and austin. you could drive around it in a day

well, not quite; that's 29° latitude, so you need to space your panels apart by a factor of 1/cos 29°, about 14%, so they don't shade each other. also in texas, unlike any other phenomenon known to humanity, it would be a bit smaller, because texas has a 25% capacity factor; the reason the usa has an overall lower solar capacity factor of 21% is that some solar farms are in suboptimal places like maine (10%) so the power doesn't require long-distance transmission

so right now it's really tough for nuclear to compete with solar on earth