Author: Zhang, Weilong
Title: Study on the overall energy performance of building window integrated photovoltaics systems
Advisors: Lu, Lin (BSE)
Degree: Ph.D.
Year: 2018
Subject: Hong Kong Polytechnic University -- Dissertations
Buildings -- Energy conservation
Department: Department of Building Services Engineering
Pages: xxiii, 173 pages : color illustrations
Language: English
Abstract: The increasing demand for energy and the simultaneously threat of global climate change have brought up the necessity to implement sustainable energy technologies. Buildings have been consuming more than one-third total final energy, resulting in an equally source of carbon dioxide emissions. Therefore, there has been an increasing awareness of promoting sustainable buildings by both improving the building energy efficiency and utilizing renewable energy technologies. In recent years, building-integrated photovoltaics (BIPV) system has become more and more popular. Due to the limited roof area in high-rise buildings, vertical facade has become the most promising area for photovoltaic (PV) integration. Windows play a vital role in building energy demand, especially when glazed facades are widely adopted in modern architectures. Therefore, how to reduce the building energy use via windows becomes an important issue. Previous studies of building window integrated photovoltaics (WIPV) systems mainly focuses on their power and thermal performances in a specific region. Limited studies were conducted on the suitability and effectiveness of different WIPV systems in different climate conditions. In addition, the daylighting performance, especially the daylight quality of the room equipped with WIPV systems is an important concern. Therefore, this thesis aims to investigate the overall energy performance of WIPV systems in different climate conditions. Both experimental and numerical studies were conducted to evaluate the power, thermal and daylighting performances of various WIPV systems, including a single-glazed semi-transparent PV (STPV) window, a semi-transparent PV insulated glass unit (PV-IGU), a semi-transparent double skin facade (PV-DSF) and a solar PV shading. Comprehensive simulation models were developed and validated with the experimental results, and then parametric studies were conducted to determine the optimum solar PV window in different climate conditions. Specifically, daylighting analysis in terms of three daylighting metrics - Daylight Autonomy (DA), Useful Daylight Illuminance (UDI) and Daylight Glare Probability (DGP) - was also carried out to evaluate the daylight quality and visual environment of the room equipped with solar PV windows.
Firstly, comparative study between single-glazed STPV window and common energy efficient windows was conducted. The results indicated that the overall energy performance of single-glazed STPV window was better than common energy efficient windows in cooling-dominated areas like Hong Kong. But the thermal insulation performance of single-glazed STPV window was quite poor, which restricted its application in cold climate regions. Then subsequent studies on the overall energy performance of PV-IGU and PV-DSF in five climate zones in China were conducted. The results showed that the PV-IGU outperformed conventional IGU in all the five climate zones. The largest energy savings were observed in Kunming where the heating and cooling energy demands are low but the solar radiation is abundant. In cold climate regions, it is better to adopted PV-IGU with higher transparency and low-E glass. Although the lighting energy consumption of PV-IGU was larger than conventional IGU, their lighting quality was better due to the higher useful daylight illuminance and lower daylight glare probability. The shallow room is more suitable for STPV window installation since the daylight autonomy reduced significantly with the depth of the room. Compared to conventional IGU, the use of conventional PV-DSFs might not be energy-efficient in cold climate regions. However, by adopting better inner glazing and appropriate ventilation modes, the PV-DSFs can outperform PV-IGU in most climate regions. Lastly, the energy saving potential of solar PV shadings with various tilt angles and orientations in Hong Kong was evaluated. The results indicate that the optimum installation position for solar PV shadings is south facade with 30° tilt angle in order to maximize the electricity generation. However, considering the electricity savings from air-conditioning system and the increased electricity consumption for artificial lighting, it is recommended that solar PV shadings should be installed on a south facade with 20° tilt angle. Furthermore, the annual overall electricity benefits of solar PV shadings were compared with the widely used interior blinds. The results showed that the well-designed solar PV shadings can achieve much more annual overall electricity benefits than the conventional interior blinds.
Rights: All rights reserved
Access: open access

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