I talk to many engineers. One of the most ideas I've ever heard is this: instead of producing electricity with solar energy, produce heat. The engineer told me that a bunch of relectors around a tank of hot water would be more efficient than solar cells. The hot water could be used to generate energy to pump itself to a nearby city, such us Las Vegas. Once primed, the system could also run pumps to pull the water into the system.

In any serious, large scale renewable energy system, the real cost is maintenance and construction. If there is enough energy to be generated, efficiency is not important.

For coastal areas, another system uses pipes that run underground into the ocean. They capture tidal action in a balloon or flywheel.