Photovoltaic solar cells can serve as a reliable source of electric power for electronic instrumentation in temporarily or permanently submerged marine systems in the form of bottom installations, buoys, or remotely controlled unmanned vehicles. The power output of submerged solar cells is a function of solar insolation intensity on the water surface, depth of submersion, optical properties of water, temperature, and the orientation of the cell surface with respect to the sun. Experimental data was generated by submerging solar cell panels in different bodies of water with 2.5 to 95 feet (0.75 to 29 meters) visibility range, as defined by the observation of a submerged standard 12-inch Secchi disc, and measuring their performance under load. The power output of horizontally oriented, upward facing, photovoltaic cells submerged to the visual contrast limit/depth was found to be a constant, equal to approximately five to ten percent of the power generated by upward facing horizontally oriented cells in atmospheric environment. At lesser depths, the power output of the cells increased, until in the splash zone the output was essentially the same as in atmospheric environment. Based on these findings it can be concluded that high efficiency silicon solar cells can serve as a practical electrical power supply in electronic devices for marine applications, providing that their depth of submersion is less than the visual contrast limit at the dive location.

ABSTRACT--Only glasses, ceramic and carbon fiber reinforced plastic can provide the necessary weight to strength ratio to make the external pressure housings for undersea vehicles positively buoyant at the abyssal design depth. This group of materials poses unique challenges to the designer and fabricator of pressure housings. This paper summarizes the findings of the R & D program aimed at developing the technology for the design, fabrication, and testing of ceramic housings culminating in the application of ceramic housings to the WHOI ROV/AUV diving system with 36,000 ft (11,000 m) capability (Figure 1).

Spherical flotation units of 99.9% Al 2 O 3 ceramic have been successfully produced by Deepsea Power & Light for application to 11 km ROV/AUV systems. The 3.6-inch (91.45 mm) OD seamless hollow spheres with 0.34 weight/displacement ratio have routinely withstood proof testing to 30,000 psi (207 MPa), 1000 hour sustained pressurization to 25,000 psi, and 10,000 pressure cycles to 20,000 psi (138 MPa). Each of the spheres provides 0.6 lb (272 gr) of lift. When encased in a 0.2-inch thick buoyant elastomeric boot, they withstood impact on concrete from a 6 ft elevation. Together with syntactic foam, they will provide most of the required lift for the WHOI HROV system with 36,000 ft (11 km) depth capability. An extensive QA procedure has been developed for each sphere, which requires not only adherence to tight dimensional and thickness specifications but also acoustic emission criteria during pressure testing.Deepsea Power & Light is also in the process of developing a roto-molding process for casting of alumina ceramic spheres with larger diameter for the whole range of ocean depths from 10,000 ft (3000 m) to 36,000 ft (11,000 m). Spheres with 5-inch (127 mm) and 8-inch (203.2 mm) outside diameter have already been successfully cast. The casting of even larger spheres will proceed upon acquisition of a larger furnace.

Fl~t disc acrylic plastic windows have been designed, fabricated, evaluated and delivered to EDU for replacement of glass windows used to date. The large (D = 6.950 inches; t -1.650 inches) and the small (D o -4.450 inches, t -1.040 inches) windows have been found on the basis of an extensive evaluation program to be more than adequate for man-rated service under 450 psi maximum operational pressure in steel flanges with D (diameter of opening in flange) of 5.000 and 3.000 inches. All windows were prooftested to 675 Fsi pressure at 120OF ambient temperature prior to delivery.

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