Following up on the discussion of underground high-voltage power transmission lines, it's worth noting a project which was under consideration in Hawaii.
Most of the state's population lives on Oahu while there are abundant geothermal resources on the big island of Hawaii. The problem is getting energy from where it is to where it is needed:
Interisland Cable -----------------
From 1982 through early 1990, a large-scale 500 megawatt geothermal/interisland submarine cable project was under consideration. About $26 million (Federal and State funding) was expended in studies, design, engineering, fabrication, and testing for the Hawaii Deep Water Cable Project.
The design criteria stated that the cable(s) would have to be able to withstand the stresses of at-sea deployment (including strong currents, large waves, and stong winds), the undersea environment (including corrosion and abrasion), and be able to reliably conduct electricity for thirty years.
Since the Alenuihaha Channel is nearly 2,000 meters deep, both deployment (laying of the cables) and operating environment posed unique engineering challenges. Over 251 different cable designs were considered. Tests included laboratory and at-sea cable deployment tests. The cable, while shown to be technically feasible through the research project, did not prove to be economical. Cost proposals for commercial installation of the cable demonstrated that the project could not be supported without significant government subsidies, which were not possible at the time.
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Like so many things, the technology is possible but just too expensive. And, unfortunately, overhead transmission lines are not an option. ;)
Regards, Will