Gaudino, Eliana (2024) Performance Analysis of High Vacuum Flat Plate Collectors, methods and results. [Tesi di dottorato]

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Abstract

Solar energy is a clean and abundant power source that can address the urgent global challenge of climate change and meet the increasing energy needs of the population. Solar heating systems offer energy independence and resilience, particularly in areas with limited access to conventional energy sources. To cater to industrial processes requiring heat, solar thermal energy systems are categorized based on their operating temperatures. Traditional flat plate collectors have limitations due to thermal losses caused by conduction, convection, and radiation. A novel solution, High Vacuum Flat Plate Collectors (HVFPCs), has emerged to overcome these limitations. HVFPCs utilize flat collectors with unconcentrated plate absorbers operating under vacuum insulation, significantly reducing thermal losses. Recent advancements have led to the development of optimized Selective Solar Absorbers (SSAs) with low emissivity, enhancing HVFPC performance. However, there is a need for energy forecasting models and performance evaluation tools specific to HVFPCs with optimized absorbers. This research focuses on analyzing and improving the performance of HVFPCs, with an emphasis on energy forecasting and technological advancements. Optimization strategies include the deposition of thin silver films on commercial SSA substrates and the development of low-emissive substrates. An efficiency model is proposed that incorporates radiative heat exchange and separates losses dependent on the absorber's optical properties from other thermal losses. Furthermore, a temperature frequency function is derived to account for the high thermal efficiency and maximum temperature achievable by HVFPCs. Experimental setups and dynamic simulation models are employed to evaluate the temperature frequency function and forecast energy production. The research also includes practical work at a solar energy company, involving performance measurements, dynamic simulations, and regulation of a HVFPCs solar field test facility. This work contributes to the optimization and evaluation of HVFPCs, providing insights into their performance and potential for industrial applications.

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