THE ELECTRICAL POWER SUBSYSTEM

The power subsystem is shown schematically in the accompanying illustration. Of the two fundamentally different types of electrical energy generating systems, open and closed cycle, only the closed cycle system in the one megawatt size is available for immediate implementation. Ideally the system will receive deep ocean water at a temperature of from 4 -6 Degrees C. and will discharge it at a temperature of 7 - 8 Degrees C. The closed cycle system is a well known thermal system. It was first demonstrated as producing net power from Ocean Thermal Energy Conversion in a facility at the Natural Energy Laboratory of Hawaii. The plant was designated as Mini-OTEC. As of this writing four such demonstration plants have been produced.

A key to the entire system is the deep ocean water pipe. Nine such pipes have been installed at the NELH. It is now clear that pipes as large as 24 inches in diameter can be installed by local fishermen and other public works technicians found in island and coastal communities. Few, if any difficulties are found in the deep ocean installation since the pipe material is buoyant and hangs in an inverse catenary which is anchored to the ocean floor in the deep and shallow waters at the pipe extremities. Survival problems can be encountered in the transition zone from sea to land. Recent successful experiments with slant drilling suggest that this technique will provide a low cost method for crossing the coastal zone.

Although the demonstration plants produced net power economic feasibility was not demonstrated until the Aluminum Company of Canada and the General Electric Company of Great Britain (now Alupower) collaborated on the development of low cost long lived heat exchangers. This was done using the conventional roll bond process employed with aluminum heat exchangers for conventional refrigerators. Extensive testing of these components and materials at the NELH permitted the design of a low cost heat exchanger module and the construction of test bed for a one megawatt system at Lynnemouth England The success o this development is maturing in a demonstration plant (200 kilowatts) for NELH which will serve as a demonstrator in a total system development as previously described.

In most small village applications there will not be an extensive or complete power grid. In such instances the best use of the OTEC electricity will be in the generation of transportable fuels. The system illustration suggests that methanol, ammonia and hydrogen are all candidates. Avery of the Johns Hopkins Applied Physics Laboratory has analyzed processes for the generation of methanol utilizing some readily available carbon source such as charcoal. He has also examined elementary processes for the manufacture of ammonia. Unfortunately neither of these processes has yet been developed for use in any system of immediate application. On the other hand the University of Kiel has developed efficient electrolytic processes which benefit from the use of cold water of high salinity. Although costly in terms of initial capital investment this process does not seem economical in the usual western financial computation. However the cost is all in the initial capitalization with a lifetime of fifty years easily achieved. Thus a capital intensive 'gift' from a development agency would relieve the donor of any further responsibility for the donee community for many years. Thus the manufacture of hydrogen will be included in the list of components which are immediately available and economically practicable. Hydrogen is certainly environmentally sustainable.
The most recent development is the receipt of the heat exchangers for the "1 megawatt closed cycle demonstration plant". The cold water effluent from this plant will be employed in the coldwater agriculture garden of the Common Heritage Corp. and may be employed for the landscaping of the power plant facility.
The other applications for the cold water effluent are discussed in the next section on the Cold Utilization Subsystem