Tidal and Wave Motion
Your current ideas of capturing energy from tidal and wave motion don't have to be technical marvels. Think paddle wheel on a pier with waves, which will create energy in both directions [waves coming and going] tied to a generator that can power dozens of neighborhoods, not full cities.
Think simple and decentralize the idea of utilities. The same goes for wind and geothermal. Think of utilities for groups of homes in a cluster. You won't have a grid failure if there is no grid. This is the way of the future, and you'll be more inclined to have it sooner than later if you do this, and it won't cost as much.
~ KRYON, through Lee Carroll, the Original Kryon Channel (via firstname.lastname@example.org)