And now for something completely different
How about an extremely low tech answer. Pipe sea water from the Gulfs of Mexico and Cortez and the Pacific into the SW US desert.
In the desert you have vast arrays of solar panels powering a system for removing the pure H2 from the water via electrolysis. The byproducts would be pure oxygen and salt. Large settling ponds would be needed to recover the salt from the resulting concentrated brine.
Electrical power needs for homes, vehicles, and business would be provided, not from large central power grids and hydrocarbons, but from individual fuel cells on site. The H2 for the fuel cells would be the pure H2 from the SW desert operation resulting in a much more effecient reaction with little degredation in the membranes of the fuel cell. The byproduct of the reaction would be water.
People living in coastal or waterfront areas could have closed systems complete from the solar panel to the fuel cells providing enough H2 to also power their automobiles.
BWTFDIK
BT