This report describes progress made by the Low-Cost Solar Array Project during the period April through August 1979. It includes reports on project analysis and integration; technology development in silicon material, large-area sheet silicon, and encapsulation; production process and equipment development; engineering and operations, and a discussion of the steps taken to integrate these efforts. It includes a report on, and copies of viewgraphs presented at the Project Integration Meeting held August 22-23, 1979.

An analytical method has been developed for determining the minimum thickness for simply supported, rectangular glass plates subjected to uniform normal pressure environmental loads such as wind, earthquake, snow, and deadweight. The method consists of comparing an analytical prediction of the stress in the glass panel to a glass breakage stress determined from fracture mechanics considerations. Based on extensive analysis using the nonlinear finite element structural analysis program ARGUS, design curves for the structural analysis of simply supported rectangular plates have been developed. These curves yield the center deflection, center stress and corner stress as a function of a dimensionless parameter describing the load intensity. Results are included for plates having length-to-width ratios of 1, 1.5, 2, 3, and 4. The load range considered extends to 1000 times the load at which the behavior of the plate becomes significantly nonlinear. Over the load range analyzed, the analysis shows that the ratio of center deflection to plate thickness for a plate of length-to-width ratio of 4 is less than 70 to 1, whereas linear theory would predict a center deflection about 1200 times the plate thickness. The stress is also markedly lower than would be predicted by linear theory. These analytical …

Silane pyrolysis in a continuous flow pyrolyzer is a simple process that is currently being developed for producing solar cell grade silicon. The process involves complex phenomena, however, including thermal decomposition of silane, nucleation and growth of silicon particles, and mass and heat transfer. Modeling the effects of transport phenomena on silane pyrolysis in a continuous flow pyrolyzer is discussed. One- and two-dimensional models are developed to predict velocity, temperature, and concentration profiles in the reactor. The one-dimensional model has been implemented as a computer code.

The retention of particulate contamination on the surface of flat-plate photovoltaic devices is adversely affecting electrical performance of outdoor-exposed modules. The results of an experimental study being performed by the Jet Propulsion Laboratory's Low-Cost Solar Array Project to characterize and understand the effects of outdoor contaminants on sensitive optical surfaces of flat-plate photovoltaic modules and cover materials are described. Comparative electrical and optical performance data from photovoltaic modules and materials subjected to outdoor exposure at field test sites throughout the United States have been collected and examined. The results show significant time- and site-dependence. During periods when natural removal processes do not dominate, the rate of particulate contamination accumulation appears to be largely material-independent. The effectiveness of natural removal processes, especially rain, is strongly material-dependent. Glass and acrylic top-cover materials retain fewer particles than silicone rubber does. Side-by-side outdoor exposure testing for long duration is presently the most effective means of evaluating soiling differences between materials. Changes in spectral transmission as a function of time and location and limited scattering data are presented.

Progress made by the Low-Cost Solar Array Project during the period April to September 1980, is reported in detail. Progress on project analysis and integration; technology development in silicon material, large-area silicon sheet and encapsulation; production process and equipment development; engineering, and operations is described. A report on, and copies of visual presentations made at, the Project Integration Meeting held September 24 and 25, 1980 are included.