This could be totally green (Score 1)

I wonder if you could design this in a way that didn't use any energy (post construction)... using ocean water (which is ostensibly cooler than the sand) and using the force of the waves, or tidal pressure to move it through the pipes.

Perhaps most simply, couldn't you fill an underground tank during high tide, and then during low tide just let the cool water leak slowly through the pipes, and then out into the ocean?

Patent!!