• Investigated multifaceted vacuum-membrane solar dish concentrator.

• Focused on mitigating membrane displacement caused by varying ambient conditions.

• Conducted experiments in a controlled indoor environment to manipulate pressure and temperature independently.

• Tested manufacturing techniques: pretension, membrane thickness, and facet sizes.

• Performed outdoor tests to assess solar radiation and wind effects on membrane displacement.

• Found smaller facets reduced membrane displacement.

• Identified Hall effect-based focus control system as most effective for stable membrane depth control.

• Improved overall optical performance and efficiency of the technology.

D. S. McGee and W. G. Le Roux, “Techniques to mitigate membrane displacement for vacuum-membrane solar-dish facets” Applied Thermal Engineering, vol. 258, Part B, pp. 124593, 2024, DOI: https://doi.org/10.1016/j.applthermaleng.2024.124593.

• Developed a novel Hall effect focus control system for sensing and maintaining membrane displacement in vacuum-membrane solar dish facets.

• Applied in small-scale concentrating solar power (CSP) systems.

• Achieved membrane displacement accuracy of 0.036 mm/°C.

• Ensured focal length stability of facets.

• Enhanced CSP system efficiency under varying environmental conditions.

Presented at the 30th SolarPACES Conference held in Rome, Italy, 8-11 October 2024

• Investigated small-scale vacuum-membrane facets for multi-faceted concentrated solar power (CSP) systems.

• Polymer-based reflective membranes adhered to elliptical television antennas to create adjustable focal lengths.

• Identified ambient temperature as the primary factor causing membrane movement.

• Developed a low-cost focus control system using diaphragm air pumps and barometric sensors.

• Reduced membrane movement to within ±2 mm limit.

• Noted the need for periodic adjustments for long-term stability.

D. S. McGee and W. G. Le Roux, “Controlled Static Environment Tests on Vacuum-Mem-brane Solar-Dish Facets for a Low-Cost Vacuum Control System,” in Proceedings of the ISES Solar World Congress (SWC23) 30 October - 4 November 2023, New Delhi, 2024, DOI: https://doi.org/10.18086/swc.2023.03.08.

• Developed small-scale solar-gas hybrid system (ST-CHP) in Pretoria, South Africa.

• Integrated vacuum-membrane faceted parabolic dish, micro gas turbine, thermal energy storage, and balance-of-plant.

• Generated electrical power and process heat.

• Achieved steady-state electrical output of 0.145 kWe and intermittent peaks up to 0.4 kWe.

• Plant performance influenced by:

  • • Dish reflector optical efficiency

    • Process piping insulation

    • Pressure losses

    • Turbine operating conditions

• Subsequent tests (without solar components) achieved 1.05 kWe output.

J. K. Swanepoel, W. G. Le Roux, C. Roosendaal, S. H. Madani, G. De Wet, T. Nikolaidis, W. Roosendaal, A. Sciacovelli, C. Onorati, Y. Liu, T. S. Mokobodi, D. S. McGee and K. J. Craig, “Initial experimental testing of a hybrid solar-dish Brayton cycle for combined heat and power (ST-CHP),” Applied Thermal Engineering, vol. 249, pp. 123275, 2024, DOI: https://doi.org/10.1016/j.applthermaleng.2024.123275.

• Investigated impact of environmental conditions on membrane depth of vacuum-membrane solar-dish facets.

• Membrane depth changes affected focal point of solar array.

• Experiments showed ambient temperature changes altered membrane depth.

• Solutions tested:

  • • Reducing air volume in vacuum cavity

    • Using alternative gases (R-134a, helium)

    • Both showed minimal improvement.

• Initial tests with non-pre-tensioned membrane showed better performance.

• Recommended further research on membrane pre-tensioning effects.

D. S. McGee, W. Roosendaal, & W. G. Le Roux, “Environmental Investigation of Vacuum-Membrane Solar-Dish Facets” in Proceedings of the 27th SolarPACES Conference 2021 (online), 27 September - 1 October, 2023, DOI: https://doi.org/10.1063/5.0149745.