phinds said:
Uh ... why would it be top secret?
Are you from another planet?
1. Anything remotely defense related, or connected to national security actually might have justifiable reasons for secrecy.
2. We have a bunch of paranoid nuts that don't require justifiable reasons to demand secrecy.
The most common reason for secrecy is that anything that large and powerful built for ordinary domestic utility purposes would also make a very fine space weapon.
Obviously, I have no idea what secrets are being kept ... if I did, I am honest enough that I would not even be posting conjecture. But to ask why governments would keep something secret ... the Pentagon would classify what they had for lunch.
I'm not sure that the topic of space solar was raised as anything important, and has thoroughly derailed the original post. The idea that in the future, we will be able to collect energy in space, and then get it to Earth is one that continues to inspire and continues to be impossible. I'm not sure why this dead horse is getting beat.
The thread topic is a bit ambiguous. I think best is a vague sort of criteria: cleanest? cheapest capital costs? cheapest operating costs? safest? lowest environmental impact? lowest greenhouse gas? I would say we should mostly stick with the toolkit of available technically feasible options, rather than hypothetical ones that are still unknown.
I agree with the comment that the situation matters. I put geothermal up in the ranking, but that has to be in the right situation. I was recently in Costa Rica, and they have several volcanoes, but they are all declared as national parks areas. So geothermal is both a practical answer for them ... the heat is right there, and impractical ... the heat is in valuable preserves. People constantly look at Yellowstone and think about the free heat. But the one-of-a-kind free heat is also a one-of-a-kind environmental wonder.
Environmental impact is one of my highest priorities. Cost would be next. Robustness of the grid would be 3rd (I do hate micro-outages).