Browsing by Author "Blomstedt, Bettina"

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    Optimisation of knitted fabrics as visually concealing covers for textile-integrated photovoltaics
    (ELSEVIER SCIENCE B.V., 2023-04) Elsehrawy, Farid; Blomstedt, Bettina; Ilén, Elina; Palovuori, Elina; Halme, Janne; Department of Applied Physics; Fashion/Textile Futures; Department of Design; New Energy Technologies
    Integrating solar cells in textiles offers a promising path toward energy-autonomous wearable electronics, but their design requires careful optimisation between energy efficiency and visual aesthetics. For this purpose, we present a systematic study of the optical properties of knitted textiles as visually concealing covers for textile-integrated solar cells. The study investigates microscopic and macroscopic factors that influence the optical performance of knitted textiles. A set of 175 samples was knitted, including 20 knit structures, 6 yarn materials, and 20 yarn colours. The knitted samples were studied using optical characterisation methods such as spectroscopy, microscopy, and photography. We developed metrics characterising solar cell performance and visual appearance, which can be used to optimise textiles based on desired performance characteristics. The strong correlation between the performance metrics demonstrates a design compromise between solar cell performance and concealment. By applying aproposed set of optimisation criteria to the knitted samples, 23 out of the 175 samples qualified as the best in solar cell performance and concealment. The developed metrics are also applicable to other textile configurations and light-sensing applications.
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    Solar knit – concealment through structure and colour
    (2020) Blomstedt, Bettina; Leppisaari, Anna-Mari; Ilén, Elina; art; Taiteiden ja suunnittelun korkeakoulu; School of Arts, Design and Architecture; Salolainen, Maarit
    Solar cells have been integrated into textiles for many years within the field of electronic textiles. Most commonly solar cells are attached on top of a textile surface, in order to harvest as much energy as possible. However, by attaching the solar cell on the surface of the textile, the aesthetics of a textile product become highly dependent on the aesthetics of the solar cell. These aesthetic limitations need to be removed in order for the technology to appeal to a larger audience and to fit into a wider range of applications. This thesis is part of a multidisciplinary research project called Sun-powered textiles. The project aim is to integrate solar cell technology into textiles in an invisible manner, and to increase the reliability of workwear safety applications by providing energy-autonomous operation through solar energy harvesting. This study aims to conceal the solar cell behind a knitted textile, whilst still letting enough light through to the solar cell. The study investigates how the different variables; material, colour and structure affect the transmittance of light of a knitted textile. In order to understand the effect of the variables on light transmittance, a library of 139 samples was knitted. The samples were measured and analysed. The physical properties of six different fibres were studied, along with the most common chemical and mechanical treatments of each fibre. The findings from the sample library were utilised in guiding the design part of the thesis; aiming to find the optimal combination of colour and structure, to create a balance between light transmittance and visual concealment. It was found that light transmittance is affected by all variables in the study. The biggest impact in transmittance is due to yarn count, yarn properties and thickness of knit. However, these factors also contribute to the visual concealment. When similar structures are compared, colour has an effect on the transmittance. The balance between visual concealment and light transmittance was most successfully achieved in structures designed to distract the eye through a colour shifting effect. This study shows that it is possible for a solar cell to harvest energy when concealed by a knitted textile. It also demonstrates that it is possible to affect the level of transmittance of the textile through material and colour choices, and the design of the knitted structure. Furthermore, the study identifies the significance of finishing treatments and their impact on the transmittance of light