| Author: | Yu, Ying |
| Title: | Study on flat-plate solar photovoltaic thermal systems for application on disaster-relief temporary shelters in Sichuan Basin |
| Advisors: | Yang, Hongxing (BSE) |
| Degree: | Ph.D. |
| Year: | 2020 |
| Subject: | Solar energy Disaster relief Photovoltaic power systems Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Building Services Engineering |
| Pages: | xxv, 216 pages : color illustrations |
| Language: | English |
| Abstract: | As natural disasters, conflicts and wars happened more frequently, the amount of victims and refugees was continuously increased, which led to a great rise in humanitarian and temporary shelters, and various forms of temporary shelters will exist for a long time. Field investigation revealed that poor thermal environment and bad living conditions in temporary shelters resulted from their poor structures and low-cost lightweight envelops. Different from employing passive technical measures for such shelters previously, this study adopted an active technique to use solar energy on site. The advances in cost-competitive solar energy utilization technologies have made it possible to be applied in post-disaster temporary shelters. Sustainability is one of the minimum standards of Sphere Handbooks, which are now applied as the de facto standards in humanitarian response. This thesis firstly discussed the energy demands for temporary shelters and reference standards for living conditions such as sanitary hot water, and then selected typical temporary shelter ---a prefab house as research target. A compact solar photovoltaic thermal (PVT) system was developed for the prefab house prototype, which can provide sustainable electricity, hot water and other services. Then its performance and applicability to the prefab house model were studied through theoretical, experimental and simulation methods. The novel roll-bond thermal absorbers with harp-channel (PVT 1) and grid-channel (PVT 2) were adopted as the key component of the two PVT experimental modules. The modified lamination process was used to combine the PV laminate with the absorber, which can reduce the heat transfer resistance between the photovoltaic panel and the absorber plate. Based on Florschuetz's PVT theory, the analytical solution of the temperature distribution of the PVT collector with roll-bond absorber was deduced, and the expression of the collector efficiency factor F' was corrected. Furthermore, the heat transfer characteristics of the PVT roof were theoretically analysed. The heat transfer control equations of the PVT collector, the roof, and the air gap formed by the PVT and roofing were established, respectively. The influence of the air gap on the heat transfer of the shelter envelop was evaluated. During one-year experiments, it was found that the two proposed PVT modules had good thermal performance and stable power generation performance, especially for the PVT 2 with grid-channel absorber. In addition, other properties of the two PVT collectors were tested and compared, including the pressure drop of the absorbers, operating modes of water circulation, the relationship between photovoltaic efficiency and shading, and the critical solar radiation levels under different operating conditions as well as stagnation temperature. According to the modified PVT theory, the numerical models of the relevant PVT in TRNSYS were modified to make them applicable to the roll-bond PVT collector without thermal resistance of its tube-to-absorber connection. The simulated values had good agreement with the experimental data, which demonstrated that the numerical models were verified by experimental data. In addition, the improved simulation method with TRNSYS can be extended to any flat-plate PVT collectors, regardless of the channel configuration in the absorber plate. Finally, for a compact PVT system integrated with the prefab house model, the annual performance and applicability were assessed, and the passive improvement effects of the PVT -roof on the indoor environment were evaluated. The results demonstrate that the system can meet the annual lighting, mobile phones and part electricity consumption of a TV or a refrigerator, at the same time, the fan and the pump power can be directly supplied by photovoltaic power. The solar fraction of the PVT system reaches 25% ~ 40% in accordance with different system locations. This application is intended to provide humanitarian care for shelter residents and make the post-disaster reconstruction sustainable. This research is solar energy application-oriented. The thesis systematically studies the adaptability of a solar photovoltaic thermal system to temporary shelters, improving the PVT structure and validating the theoretical model, and paying attention to system performance in accordance with the dynamic loads of demands. It has accumulated the experience in the operation and control of the system applied in Sichuan Basin, and made efforts to promote the practical application of the PVT system, which has great theoretical significance and engineering application value. |
| Rights: | All rights reserved |
| Access: | open access |
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