Dye-sensitized solar cells are subject to intensive research nowadays. Their open-circuit voltage, short-circuit current, and efficiency depend on several parameters which can be optimized. Here, examinations are limited to non-toxic substances due to planned future application on textile fabrics, i.e., to TiO2, graphite, and natural dyes. During experiments on the TiO2 layer, the reproducibility of the experiment turned out to be a crucial factor, limiting the significance of the experimental findings. Thus, the main goal of this paper is the description of possibilities to standardize the production under laboratory conditions by eliminating distorting factors. Specifically, the pressure by which the glass plates with conductive coatings, serving as electrodes, are pushed together to close the solar cell was found to significantly influence the results. Different possibilities were hence tested to normalize this pressure, including different clamps and magnets. In the optimal setup, the deviations between nominally identical cells could be reduced by one order of magnitude.

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Putting renewable energy to good use is necessary to deal with one of the greatest challenges of our time, namely, climate change. One problem, however, is that the technology we are using today turns into toxic waste at the end of its useful life, which in particular concerns the blades of wind turbines. We investigated how the ideas of a circular economy can be applied to address this issue. To this end, we built a small wind turbine almost entirely from used mAterials. The social purpose of this is to raise public awareness about renewable energy technology that is part of a circular economy. Therefore, we chose a reliable and easy-to-build concept for a small wind turbine, which can be reproduced in a "Do It Yourself" (DIY) approach. The core challenges we had to face consisted of how to acquire appropriate used mAterials and how to improve the efficiency of the system to obtain adequate electrical power. With a financial investment of less than €100, we built a Savonius wind turbine for use in, for example, a private garden to charge a power bank or other USB-chargeable devices.

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In a world with growing demand for resources and a worsening climate crisis, it is imperative to research and put into practice more sustainable and regenerative products and processes. Especially in the energy sector, more sustainable systems that are recyclable, repairable and remanufacturable are needed. One promising technology is dye-sensitized solar cells (DSSCs). They can be manufactured with low energy input and can be made from non-toxic components. More than 70% of the environmental impact of a product is already determined in the design phase of a product, which is why it is essential to implement repair, remanufacturing and recycling concepts into the product design. In this publication, we explore appropriate design principles and business models that can be applied to DSSC technology. To realize this, we applied the concept of Circo Track, a method developed by the Technical University of Delft, to DSSCs and investigated which design concepts and business models are applicable. This method enables companies to transform a product that is disposed of after its useful life into one that can be used for longer and circulates in material cycles. The most important result is the description of a performance-based business model in which DSSCs are integrated into the customer’s building and green energy is provided as a service. During the operational phase, data is collected for product improvement and maintenance, and repair is executed when necessary. When the contract expires, it can be renewed, otherwise the modules are dismantled, reused, remanufactured or recycled.