The report describes the philosophy which is being followed in approaching the problem of the transmission of bulk electric power at very high voltages by means of long distance submarine cables laid in exceptionally deep waters up to 5000/6000 ft.
After a careful survey of the present state of the art for all possible candidate cables, it is planned to focus attention on the most promising ones with reference to some representative sites of future OTEC plants. It is intended that the chosen cables will undergo full technical design, economic evaluation and reliability analysis.
If candidate cables, according to the state of the art, are not sufficiently developed for one or more representative sites, then suitable research and development work will be proposed. Attention is also paid to cable accessories and laying operations, with special emphasis on the importance of reducing the number of joints, on the exceptional performance required for the laying equipment and on the embedment problem.
After covering the main problems of the bottom cables connecting the substations on the shore end to the proximity of the OTEC power plants, some hints are provided on the interface with the riser cables connecting the standing bottom cables to the floating power plants.
A number of plants for Ocean Thermal Energy Conversion (OTEC) are contemplated for production of 250 MW to 500 MW plant output, taking advantage of the temperature differences between surface and deep waters in suitably chosen sites. Plant sites ranging from a few nautical miles to some hundred nautical miles off-shore with water depths up to 5000/6000 ft (1500-1800 m) requires careful consideration of design, manufacture, installation, maintenance and repair on the submarine power cable system transmitting the electric power from plant to shore before complete plant requirements can be specified.
The electric power transmission system for the OTEC floating plants is contemplated to consist of two phases:
Phase I, selection of the most promising cable systems from among possible alternatives for various plant sites plus suggestion of research and development work necessary to define suitable cable solutions when the present state of the art is insufficient.
Phase II, detailed design of the selected cable systems for various plant sites including fabrication and test of experimental cables and accessories when required, leading to final specifications for use with OTEC plants.
These phases are further divided into two segments, covering:
the bottom cable, going from the shore to the connector of the riser cable;
the riser cable, connecting the bottom cable to the floating plant.
The study of the riser cable also includes the submarine connection to the bottom cable at one end and the integral cable suspension system at the other end.
The two segments are developed separately but not independently, and must be mutually compatible in design and operation.