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Development of low-cost focus control systems for vacuum-membrane solar dish facets
Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2024.
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| Format: | Thesis |
| Language: | English |
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University of Pretoria
2024
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| _version_ | 1867613694384406528 |
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| access_status_str | Open Access |
| author2 | Le Roux, Willem G. |
| author_browse | Le Roux, Willem G. |
| author_facet | Le Roux, Willem G. |
| collection | Thesis |
| dc_rights_str_mv | © 2023 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2024. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/97314 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:40:13.301Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2024 |
| publishDateRange | 2024 |
| publishDateSort | 2024 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/97314 Development of low-cost focus control systems for vacuum-membrane solar dish facets Le Roux, Willem G. duncan.mcgee@tuks.co.za McGee, Duncan Sean UCTD Sustainable Development Goals (SDGs) Concentrating solar power Multi-faceted concentrator Vacuum-membrane Focus control system Hall effect Engineering, built environment and information technology theses SDG-07 SDG-07: Affordable and clean energy Engineering, built environment and information technology theses SDG-09 SDG-09: Industry, innovation and infrastructure Engineering, built environment and information technology theses SDG-12 SDG-12: Responsible consumption and production Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2024. Concentrating solar power (CSP) is a growing method of harnessing energy from the sun for generating electricity and process heat, especially in South Africa which boasts one of the most plentiful solar resources globally. A small-scale CSP system, consisting of a multi-faceted concentrator that employs vacuum-membrane technology, is actively being developed at the University of Pretoria. The facets constituting this innovative design are constructed from a reflective polymer-based membrane adhered to the rims of readily available and cost-effective elliptical television antennas. A crucial step involves creating a vacuum within each facet, forming a near-parabolic membrane shape. Previous studies found that the membrane depth shifts slightly due to varying ambient conditions throughout an operational day. These slight depth shifts lead to major focal point shifts, reducing the CSP system’s overall efficiency and performance. The first goal of this research was to examine in more detail how static ambient conditions impact the displacement of membranes used on vacuum-membrane solar-dishes. A controlled-environment enclosure was employed to achieve this, allowing for the independent manipulation of a facet’s ambient pressure and temperature. The second goal was to investigate methods to mitigate membrane displacement. Various manufacturing techniques were investigated within the controlled-environment enclosure, which included alterations in pretension, changes in membrane thickness by removing the removable plastic layer on the EverBright mirror film, and adjustments to overall facet sizes. Results revealed that ambient temperature impacted the membrane displacement significantly more than ambient pressure. It was also determined that opting for a small facet with a thin membrane and high pretension will effectively minimise membrane displacement. This, however, would not suffice to mitigate membrane displacement. The outdoor test results of a facet without a focus control system indicated that solar radiation, specifically global horizontal irradiance (GHI), affected the internal temperature (depending on the wind velocity), and therefore also affected the membrane depth. Furthermore, to further reduce membrane displacement, low-cost focus control systems were investigated. A focus control system for USD 29.34 maintained a constant differential pressure for a vacuum-membrane facet within the required accuracy of ±2 mm membrane displacement. An attempt was made to further mitigate membrane displacement by incorporating the effects of temperature on membrane stiffness, which demonstrated slight improvements. A focus control system consisting of a low-cost Hall effect module actively monitoring membrane depth emerged as the most effective in eliminating membrane displacement, with an increase of about 0.09 mm and a decrease of approximately 0.02 mm from an initial depth of 10 mm. This level of stability will ensure that the facet maintains a consistent optical performance, ultimately advancing the reliability and efficiency of low-cost vacuum-membrane technology. Special thanks to the Renewable Energy Hub and Spokes Program of the Department of Science and Innovation (DSI) for financial support through the UP Solar Thermal Spoke. mi2025 Mechanical and Aeronautical Engineering MEng (Mechanical Engineering) Unrestricted Faculty of Engineering, Built Environment and Information Technology SDG-07: Affordable and clean energy SDG-09: Industry, innovation and infrastructure SDG-12: Responsible consumption and production 2024-07-30T07:35:27Z 2024-07-30T07:35:27Z 2024-09 2024-07-25 Dissertation * S2024 http://hdl.handle.net/2263/97314 DOI: https://doi.org/10.25403/UPresearchdata.26397742.v1 https://doi.org/10.25403/UPresearchdata.26397742 en © 2023 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | UCTD Sustainable Development Goals (SDGs) Concentrating solar power Multi-faceted concentrator Vacuum-membrane Focus control system Hall effect Engineering, built environment and information technology theses SDG-07 SDG-07: Affordable and clean energy Engineering, built environment and information technology theses SDG-09 SDG-09: Industry, innovation and infrastructure Engineering, built environment and information technology theses SDG-12 SDG-12: Responsible consumption and production Development of low-cost focus control systems for vacuum-membrane solar dish facets |
| title | Development of low-cost focus control systems for vacuum-membrane solar dish facets |
| title_full | Development of low-cost focus control systems for vacuum-membrane solar dish facets |
| title_fullStr | Development of low-cost focus control systems for vacuum-membrane solar dish facets |
| title_full_unstemmed | Development of low-cost focus control systems for vacuum-membrane solar dish facets |
| title_short | Development of low-cost focus control systems for vacuum-membrane solar dish facets |
| title_sort | development of low cost focus control systems for vacuum membrane solar dish facets |
| topic | UCTD Sustainable Development Goals (SDGs) Concentrating solar power Multi-faceted concentrator Vacuum-membrane Focus control system Hall effect Engineering, built environment and information technology theses SDG-07 SDG-07: Affordable and clean energy Engineering, built environment and information technology theses SDG-09 SDG-09: Industry, innovation and infrastructure Engineering, built environment and information technology theses SDG-12 SDG-12: Responsible consumption and production |
| url | http://hdl.handle.net/2263/97314 https://doi.org/10.25403/UPresearchdata.26397742 |