Simulation and experimental investigation on optimum applications of the shading-type BIPV and BIPVT systems on vertical building facades

Abstract

Among the various types of renewable technology, solar photovoltaic has the potential for large scale applications in the future due to its clean nature and decreasing cost in recent years. Building Integrated Photovoltaic (BIPV) and Building Integrated Photovoltaic Thermal (BIPVT) are both common applications of photovoltaic technology. In recent years, BIPV and BIPVT technology applications have been developed rapidly because of its unique characteristic, i.e. to combine clean power production with other functional features on building facade and hot water production. Although a number of reports have been published for the BIPV and BIPVT applications, there are still problems to be solved, especially for their application in high-rise buildings. In Hong Kong, most of the buildings are high-rise buildings. Most people live in small to medium flats. There is not enough roof area for locating photovoltaic (PV) modules for solar energy application on the roofs of the buildings. If the PV module can be used on vertical facades of such high-rise buildings, the less roof are problem can be solved for solar energy applications. This thesis aims to investigate how to use solar photovoltaic effectively on vertical facades of high-rise buildings. Firstly, the energy performance of the shading-type BIPV claddings on vertical buildings’ facade is analyzed by using a dynamic heat transfer method. A 2D numerical model was developed to explore the impacts of building orientations, inclinations and wall utilization fractions on the energy performance of the shading-type BIPV claddings in terms of annual power output of PV modules and cooling load reduction of windows and concrete walls. When the area of PV modules is considered, the maximum electricity saving of the shading-type BIPV claddings could be 239.5kWh/m², which is twice of the maximum electricity generation of the PV modules alone. It is indicated that the shading-type BIPV claddings can significantly increase the total energy benefits relative to PV modules. It is thus a good choice to apply the shading-type BIPV system in buildings like in Hong Kong. Secondly, in order to further improve the energy performance of the BIPV system, a quasi 3D dynamic simulation model was developed to evaluate the energy performance of the BIPVT hot water system under natural circulation. A test rig was set up and calibrated for this study. An experimental study was carried out in the solar simulation lab of the Department of the Building Services Engineering and the predicted results were then compared with experimental data to evaluate the numerical simulation accuracy. The experimental measurements taken in the full scale indoor test facility are in good agreement with the predicted results. In addition, the influence of the configuration parameters of the BIPVT module has been analyzed. The simulation results show that the configuration parameters of the BIPVT module should be optimized to maximize its energy performance. The fact is that a little change of the configuration parameters of the BIPVT module can significantly increase the energy performance of the PV module, especially the thermal efficiency of the BIPVT module. At last, a building-integrated photovoltaic-thermal (BIPVT) energy system designed for a flat of two residents is proposed for generating electricity and producing hot water from vertical facade of high-rise residential buildings in Hong Kong. The annual hourly energy performance simulation of the system was conducted on the basis of dynamic heat transfer analysis and the typical meteorological year (TMY) weather data of Hong Kong. The simulation results obtained from a case study indicate that the proposed BIPVT hot water system can effectively increase the total energy benefits compared with a photovoltaic (PV) system integrated on vertical building facades. When the BIPVT modules are connected in series, the electrical energy efficiency, thermal energy efficiency and combined energy efficiency of the BIPVT system are, respectively, 10.0%, 34.9% and 44.9%. Such a system can offer 82.3% of the annual hot water supply to the flat in a year. The proposed system is found to be suitable for vertical facade of high-rise residential buildings in Hong Kong so that the problem of limited roof area in a high-rise building can be solved for solar energy application in a density urban area like Hong Kong.