Abstract
In recent years, the German Aerospace Center (DLR) developed Gossamer deployment systems in different projects. As power requirements of spacecraft are getting more and more demanding, DLR recently focused on the development of new deployable photovoltaic (PV) technologies that are suitable for generating 10’s of kW per array. Possible space applications that may also require high power supply are missions using electric propulsion such as interplanetary missions, placing of geostationary (GEO) satellites in their orbit or even more future oriented as space tugs or lightweight power generation on extra-terrestrial infrastructures. The paper gives an overview about a feasibility study for flexible solar arrays based on new thin-film photovoltaics. It is expected that the combination of new thin-film PV technologies, e.g., copper indium gallium selenide (CIGS) cells or gallium–arsenide (GaAs) cells, together with Gossamer deployment technologies, could significantly increase the power availability for spacecraft. Based on a requirement, analysis system concepts were evaluated. A focus is on the potential of CIGS PV combined with a two-dimensional deployment of the array and DLR’s coilable carbon fibre-reinforced plastic (CFRP) booms. Therefore, a concept based on crossed booms with a foldable PV membrane is considered as baseline for further developments. The array consists of rectangular PV generators that are interconnected by flexible printed circuit board (PCB) harness. By a double-folding technique, these generators are laid on top of each other in such that the membrane can be extracted from its stowing box during the deployment in a controlled manner. Considering constantly increasing efficiencies of the CIGS PV combined with Gossamer structures, there is clear potential of reaching a very high specific power value exceeding that of conventional PV systems. Furthermore, the CIGS PV appears to be more radiation resistant and has already reached more than 21% efficiency in laboratories. Such efficiencies are expected to be achieved in the near future in a standard manufacturing process. However, flexible, thin-film GaAs cells are also subject of consideration within GoSolAr. With this prospect, DLR’s research has the goal to develop a Gossamer Solar Array (GoSolAr) to exploit the described potential.
Highlights
The goal of the Gossamer Solar Array (GoSolAr) activity is to develop a technology for large PV arrays based on a two-dimensional deployment combined with flexible PV and to demonstrate the functionality in-orbit
Membrane and deployable booms shall be robust against a higher number of deployments
One additional combined deployment test using a membrane with the flex printed circuit board (PCB) hinge Type D has already been performed and showed an advantageous behaviour compared to the one described hereafter
Summary
In view of technology demonstration, a single PV generator strategy is followed, where each PV generator is connected to the GoSolAr power conditioning and characterisation electronics individually This enables maximum flexibility regarding accommodation of PV generators of different technology in different locations on the blanket as well as maximum flexibility for characterisation measurements. With each PV generator having its own power tracks as well as electrical measurement tracks, arbitrary electrical string connections can be defined with correspondingly different output voltages by suitable multiplexing units within GoSolAr’s electronics. This maximizes the design independence from the satellite bus battery charging concept in terms of end of charge voltage. It is understood and accepted that by this single PV generator approach, unnecessarily long electrical connections with corresponding losses are introduced
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