Innovative Solutions For Microsatellites Photovoltaic Power Generation

Paper number

IAC-07-C3.2.03

Author

Ms. Daniela Cipollone, Scuola di Ingegneria Aerospaziale, Italy

Coauthor

Ms. Lucrezia Murrali, Scuola di Ingegneria Aerospaziale, Italy

Coauthor

Prof. Fabio Santoni, University of Rome "La Sapienza", Italy

Coauthor

Dr. Fabrizio Piergentili, University of Bologna, Italy

Year

2007

Abstract

UNISAT program is an educational project with the aim to involve students in designing, manufacturing and operating in orbit microsatellites, established in late nineties at the School of Aerospace Engineering, University of Rome “La Sapienza”. The Unisat whole technological process  has been developed on the basis of the terrestrial technology,  modified to make the system withstand the launch  and space environment loads. In this perspective the attention of our group is now turned to terrestrial concentrator systems in order to evaluate their reliability for low-cost microsatellite EPS (Electrical Power Subystem). In a  concentrator system, high efficiency solar  cells enable greater power generation  capacity for a given concentrator size, thus  reducing the cost per watt of all system  components. A concentrator makes use of inexpensive materials such as plastic lenses to capture solar energy shining on a fairly large area and focus that energy onto a smaller area, where the solar cell is. In order to reduce the costs, most of the UNISAT satellites components are based on commercial off the shelf components which are supposed to be durable  in space environment, such as solar cells. In this project we would test terrestrial high efficiency triple-junction cells. Fabricated using space solar cell device structures,  they were modified for optimum performance under terrestrial spectrum. The principal difference were a  thicker doped  emitter  to  reduce  distributed  sheet  resistance  losses at high  concentration, and  a thicker   GaInP2 top cell to achieve current matching under an  AM1.5 spectrum. There are also built-in manufacturing changes relating to different radiation exposure but many researches confirm that terrestrial cells can be adopted without any modification for space  missions which radiation environment  is not severe, such  as short term, low earth orbit. The development of a collector module requires a lens of large aperture and short focal length without the weight and volume of material which would be required in conventional lens design: Fresnel lens. It reduces the amount of material required compared to a conventional lens by breaking the lens into a set of concentric annular sections in which the overall thickness of the lens is decreased, chopping the surface into a set of surfaces of the same curvature. 
In order to keep low UNISAT program cost carrying out new technological challenges, we would  exploite this new technology with the aim to use something innovative and more efficient in low cost microsatellite power system.  

Abstract document

IAC-07-C3.2.03.pdf

Manuscript document

IAC-07-C3.2.03.pdf (🔒 authorized access only).

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