by
Robert Cohen
Mega Marine Structures, Inc.
U.S.A.
An innovative, low-cost, fiber-reinforced-polymer honeycomb (FRPH) sandwich composite is being introduced for marine applications (cf. Sea Technology, April 1993). Corrosion-resistant FRPH structural elements are applicable to many components of land-based and floating OTEC plants, with OTEC cold water pipes (CWPs) being a likely early application. Prototype 2.5-meter diameter cylindrical underground FRPH fuel-storage tanks - which resemble OTEC CWPs - have been tested by Underwriters Laboratories. At CWP diameters of about one meter or greater, relatively low-density FRPH CWPs appear to be economically attractive compared to CWPs made of solid FRP. FRPH CWPs could be built having diameters of 30 meters or greater. A 10-meter diameter FRPH CWP, for example, would employ outer and inner skins about one centimeter thick. The outer skin would be filament-wound. To adjust the FRPH CWP's buoyancy, the nested-wave core, about 15cm thick, would be partially flooded with sea water via pressure-equalizing vents in the top of the pipeline. Pipe-section lengths ranging from about 20 to 35 meters would probably be employed, although it would be possible to construct a continuous pipeline without joints by forming it in a "spiral-wrap" operation (much as cardboard tubes are manufactured).