SOLAR -- THE VIABLE KIND

This leaves virtually only the vast area of the oceans as solar collectors: They not only already collect solar energy, but they also store it during the night and on cloudy days (another major obstacle to large-scale, land-based solar energy conversion).

We have previously described the Ocean Thermal Energy Conversion (OTEC) idea, particularly the use of the temperature difference between the surface and deep water to run vapor turbines with ammonia as the working fluid (Dec.1973, Nov.1974). There have been many discussions on the point. (See Proceedings, 3rd OTEC Workshop, Houston, 1X. May 1975, publ. by Appl. Phys. Lab., Johns Hopkins U., Laurel, MD 20810.)

But there are now concrete, if preliminary, blueprints of practical systems. The two leaders are TRW Inc. and Lockheed, whose designs differ in several respects. Lockheed's plant, most of which is under water, swivels about its mooring cable, which gives it more stability in storms and ocean currents. It has four power modules of 40 MW output each; these modules may be individually separated from the platform (for maintenance) without interrupting the operation of the remainder of the power plant. Another novelty is a telescoping pipe consisting of five 200-ft sections, which brings up the cold water from depths of 1500 feet or more. The pipe (105 to 129 ft in diameter) is retracted for towing the main platform into position; the modules are towed separately, and then secured to the main body by hydraulic locking arms.

Lockheed's spokesmen are optimistic perhaps overly so. They believe that by building 25 or more of such 160 MW plants at a time, they can get the cost down to $1,250 per installed kW (compared to slightly more than $1,000 for a nuclear plant) and that, given the go-ahead (i.e., an ERDA contract), they can have a plant in commercial operation by 1986.

Neither promise is particularly enticing, but plans for OTEC plants are now approaching the point where they might become economically competitive.

Apart from the inexhaustible fuel, they have another advantage: They could be mass-produced in shipyards to standard specifications - a costcutting feature unattainable in custom designed land-based power plants.