Quote Originally Posted by Thomar_of_Uointer View Post
These can actually be solved together. As you've probably already figured out, geothermal energy is really easy to work with at the bottom of ocean trenches. It can also be directly harnessed to heat habitats, keeping everyone warm. You may also have major temperature variations across a settlement, with places near the power pipes unbearably hot and the less-inhabited outskirts almost freezing cold. Also note that because of the pressure ice will form at much lower temperatures. Ice may be unheard of.
Wouldn't building in a deep ocean trench create huge problems with making your dome hold up to the pressure compared to building in shallower water?

I'd go with nuclear fission or fusion. You can extract the fuel for either one from ocean water, and you don't have to be in a trench to do it.