Session
Technical Session I: Advanced Component Developments
Abstract
Recent advancements in photovoltaic solar cells made from Gallium Arsenide (GaAs) have shown that with concentration ratios greater than one solar constant, overall efficiencies up to 23% can be achieved. A second issue applicable to solar power systems for spacecraft is the cost driver, which requires that the efficiency/weight ratio be improved so that solar panels with high output, weighing less, will reduce payload weights, which, in turn, reduces launch costs. This has resulted in a "Figure of Merit" being introduced to grade the characteristics of solar panels for spacecraft. This Figure of Merit defines a ratio of watts/kilogram for a solar panel. Typical flat plate panels on current spacecraft, fabricated with silicon solar cells without concentration, provide Figures of Merit of 25 to 30 watts/Kg. This paper describes a new design of a 1.9/1 solar concentrator in which conservative calculations show improvements on this Figure of Merit by a major factor (3 to 4). An alternate 2.88/1 concentrator configuration using larger GaAs cells, thereby greatly reducing the number of cells per panel, and thereby reducing the complexity of the solar panel assembly, is also presented and has been analyzed to show an equivalent Figure of Merit. The proposed flat solar panel is a mosaic arrangement of modular 5 mm. x 5 mm. GaAs cells in a rectangular "honeycomb" type grid, which performs the triple function of: 1. Optical Concentrator. 2. Basic structure for the Solar Panel, having a thickness of 1/5 of current solar panels. 3. Current carriers for the solar power generated by the cells. The cells are optically immersed in a "Cassegrainian-type" fused silica concentrator which, through the use of total internal reflection, produces no obscuration and achieves a wide field of view to ease the tracking requirements for the solar panel. (Patent Pending). The computed Figure of Merit for this design has been computed to be >126 watts/Kg., or over four times the current capabilities of the best flat plate solar panels. A second design is also presented which uses a stamped pyramidal reflective concentrator on an immersed solar cell, allowing larger cells and fewer cells per panel. This design has a computed "Figure of Merit" of 158 watts/Kg. The panel in either design is designed for an automated assembly process necessary in order to reduce the cost. The paper describes this proposed automated fabrication assembly process, based upon current "Pick and Place" PC board assembly technology. The Van Allen radiation survivability of this design is also addressed in the paper.
Description of an Immersed Photovoltaic Concentrating Solar Power System
Recent advancements in photovoltaic solar cells made from Gallium Arsenide (GaAs) have shown that with concentration ratios greater than one solar constant, overall efficiencies up to 23% can be achieved. A second issue applicable to solar power systems for spacecraft is the cost driver, which requires that the efficiency/weight ratio be improved so that solar panels with high output, weighing less, will reduce payload weights, which, in turn, reduces launch costs. This has resulted in a "Figure of Merit" being introduced to grade the characteristics of solar panels for spacecraft. This Figure of Merit defines a ratio of watts/kilogram for a solar panel. Typical flat plate panels on current spacecraft, fabricated with silicon solar cells without concentration, provide Figures of Merit of 25 to 30 watts/Kg. This paper describes a new design of a 1.9/1 solar concentrator in which conservative calculations show improvements on this Figure of Merit by a major factor (3 to 4). An alternate 2.88/1 concentrator configuration using larger GaAs cells, thereby greatly reducing the number of cells per panel, and thereby reducing the complexity of the solar panel assembly, is also presented and has been analyzed to show an equivalent Figure of Merit. The proposed flat solar panel is a mosaic arrangement of modular 5 mm. x 5 mm. GaAs cells in a rectangular "honeycomb" type grid, which performs the triple function of: 1. Optical Concentrator. 2. Basic structure for the Solar Panel, having a thickness of 1/5 of current solar panels. 3. Current carriers for the solar power generated by the cells. The cells are optically immersed in a "Cassegrainian-type" fused silica concentrator which, through the use of total internal reflection, produces no obscuration and achieves a wide field of view to ease the tracking requirements for the solar panel. (Patent Pending). The computed Figure of Merit for this design has been computed to be >126 watts/Kg., or over four times the current capabilities of the best flat plate solar panels. A second design is also presented which uses a stamped pyramidal reflective concentrator on an immersed solar cell, allowing larger cells and fewer cells per panel. This design has a computed "Figure of Merit" of 158 watts/Kg. The panel in either design is designed for an automated assembly process necessary in order to reduce the cost. The paper describes this proposed automated fabrication assembly process, based upon current "Pick and Place" PC board assembly technology. The Van Allen radiation survivability of this design is also addressed in the paper.
