Foldable Solar Arrays for Small Satellites: A Technology Study on Scalable Manufacturing and Space Qualification

Kurzfassung

The growing number of spacecrafts and the strategic ambition to reduce dependence on non-European, export-controlled components have renewed interest in ITAR-free photovoltaic solutions for space applications. This thesis investigates how emerging European photovoltaic technologies can be integrated into space-relevant solar string architectures and focuses in particular on the role of electrical interconnection as an enabling technology. First, a structured analysis of the European photovoltaic manufacturer landscape is carried out, identifying promising actors in high-efficiency silicon, tandem perovskite–silicon, and flexible devices. While these technologies offer attractive specific power and design flexibility, most of them have not yet undergone comprehensive space qualification, and industrial production capacities remain limited. This highlights the need for integration concepts that are both technology-agnostic and compatible with fragile or still maturing cell concepts. On this basis, a conceptual framework for product integration is developed, defining a common reference string architecture and a set of key performance indicators at string level. The framework covers electrical metrics (maximum power point, efficiency, temperature coefficients), mass and area efficiency (areal power density, specific power), and interconnection-related indicators (contact resistance, mechanical robustness, process repeatability). It serves as a generic template for comparing different cell technologies under comparable boundary conditions. Due to practical constraints in solar cell availability, the experimental work shifts from comparing cell technologies to comparing interconnection methods for solar strings. Parallel gap resistance welding is investigated through a process parameter study, revealing a narrow and sensitive process window in which small deviations in welding current, pulse duration, electrode force, or active overlap area lead to pronounced changes in weld quality and contact resistance. Electrically conductive adhesives - including anisotropic conductive adhesive systems and copper-based busbar tapes - are then evaluated as a lower-temperature, mechanically more sensitive alternative. The tested adhesive joints achieve contact resistances of similar order with relatively low scatter and are easier to process manually, but their long-term stability under space-relevant environmental loads remains to be demonstrated. The results underline that interconnection is a critical design variable in the development of future European space photovoltaic systems. Robust metallurgical joints such as resistance welds and more forgiving adhesive-based approaches each occupy distinct niches in the design space, especially when interfacing advanced or fragile cell technologies. The framework and findings presented in this thesis provide a basis for future qualification campaigns and technology demonstrations aimed at transferring advanced terrestrial photovoltaic developments into reliable, ITAR-free power systems for the space sector.