Created by the AI Vin
Tech Level: Stringtech 3
Cost: Public Domain for the design, Moderate for implementation
Tech Level: Stringtech 4
Tech Level: Stringtech 5
I remember reading about this sort of stuff in Popular Science back in the late 70's, early 80's. Anyway, this strikes me as the sort of thing that might come up in the background or the be the reason for an Inspector visit.
Edited for Wikipedia Link on OTEC.