Geothermal air conditioning. It works 3-4 times better than average air conditioners.

It will have to be a combination. We need to look locally at what resources are most easily available. Wind would never work in my city, but solar is great. I believe we have tapped all the rivers we can, so traditional hydro methods can’t expand. We should encourage as many technologies as we can, they will only improve production and efficiency with practical application.

Combination, for sure, taking into account local differences such as wind and amount of sunlight. Wind and solar make a nice combination, as one is strong during the times the other is weak.

Geothermal is reliable but I wouldn’t want it in an earthquake area.

Conservation is the easiest and most promising of all.

I don’t look for a silver bullet, and think a diversity of solutions is our best option.

It will have to be a combination of different sources. You don’t have biofuels on there which could change everything once they figure out cellulaic alcohols. If they can improve energy storage it would also be a huge change.

Another technology which is mostly ignored is reducing the need for energy such as installing insulation and low usage appliances.

you cannot scale up hydro or geothermal.
there is a limit.
wind and solar are better, although solar is only good a few hours a day.
not sure what you mean by hydrogen, but since there isn’t any free hydrogen to burn, that’s obviously not going to work.

i think that Lawrence Livermore NIF is coming close to demonstrating a viable fusion reactor.
if you live anywhere near, i think they conduct weekly tours.
but they have to do a background check.
.