Firstly, this paper introduces a novel multi-functional BIPV/T wall system in order to satisfy building's seasonal energy demand in China. This system can generate electricity during the whole year. In heating season, hot air is created to decrease heating load for the building. In non-heating season, hot water is generated to supply the household demand. Meanwhile temperature of PV panel is decreased by water cycle, therefore higher electrical performance is able to be achieved. Secondly, mathematical model is established and verified by the experimental results. Thirdly, annual performance of the system in three different typical cities are evaluated. The annual electrical generation in Beijing, Hefei and Xining are 247.7 kWh, 152.6 kWh and 268.4 kWh respectively. The solar fraction in Beijing, Hefei and Xining are 49.9%, 38.7% and 41.3% respectively. The system is able to satisfy 79.1%, 66.8% and 60.4% hot water energy demand in these cities respectively. The overall annual energy saving in Beijing, Hefei and Xining are 2661.8 kWh, 1908.4 kWh and 2412.3 kWh respectively. Fourthly, the impact of external/internal PV structures, Si/CdTe solar cells and aspect ratio of the system are investigated respectively. (C) 2020 Elsevier Ltd. All rights reserved.

PV/T systems are developed to obtain electrical & thermal energy simultaneously. Generally, in PV/T system where PV cells are laminated on absorbing plate (A-PV/T), the cells can be damaged due to high temperature, thermal stress, electrical insulation problem and absorbing plate deformation. Consequently, the reliability of PV cells limits the wide application of A-PV/T systems. Moreover, the electrical performance is affected by high cells' temperature. To overcome these problems, proposed a new structure of a PV/T system where cells are laminated on the back of glass cover (G-PV/T) instead. Experimental and numerical investigations are performed to explore the performance of two systems. The G-PV/T shows a lower temperature and better photovoltaic performance with the daily electrical efficiency of 11.66% (which of A-PV/T is 9.74%), thermal efficiency of 28.4%, and final water temperature of 45.6 degrees C. Two 3D dynamic thermal/electrical models are also proposed, which shows good agreement with experimental data. The influences of various structural parameters (PV coverage ratio, thickness of absorbing plate, thickness of air gap) on both PV/T systems have been predicted and compared. Furthermore, two mechanical models are proposed to explore the thermal stress distributions across the cells as well as provide an economic analysis of two systems. (C) 2019 Elsevier Ltd. All rights reserved.

Traditional BIPVT systems are faced with the seasonal use issues that they run efficiently only during certain parts of the year, and perform poorly or even out of service for the rest of the time. To overcome the problems, this paper performs several tasks as follows. (1) A hybrid photovoltaic-water/air solar wall (HPSW) system is presented, which combines the air cooling channel and water cooling channel together in one single BIPVT system. (2) The HPSW system can run three modes according to different seasonal needs of the building: (1) PV/Air mode in winter, (2) PV/Water mode in summer, (3) PV-water/air mixing mode in transition season, which means that the new system is able to satisfy annual demands of the buildings. (3) The HPSW system were experimentally tested in different seasons under different modes during a whole year. (4) The results showed that the all-day average electrical efficiency can reach 15.3% by PV/Air mode in winter, 7.8% in summer and 11.6% in transition season by PV/Water mode. The average daily power generation of the system in summer, transition season and winter was 973.0 kJ, 3226.4 kJ and 4460.5 kJ, respectively. As for thermal performance, the PV/Water mode performed well both summer and transition seasons, with the average thermal efficiency of 55.1% and 51.5% respectively. The temperature rise of experimental room reached 8.1 degrees C compared to the reference room in winter. The results proves that the HPSW system can operate efficiently as expected throughout the year and has great value in different seasons and different regions.

A built-middle PV Trombe wall (MPVTW) with solar PV panel installed in the middle of the air channel is proposed, designed, and manufactured in the present study. Comparative tests with the traditional built-external PV Trombe wall (EPVTW) were conducted in Hefei (117 degrees E, 32 degrees N), China to evaluate the performance of the MPVTW system. The average electrical and thermal efficiencies of the MPVTW system were measured as approximately 12.0% and 38.2%, respectively. The average value of the total efficiency of the MPVTW system was 10.83% higher than that of the EPVTW system. In addition, the effects of different parameters (i.e. channel height, the PV cells coverage ratio, and the PV cells position) on the energy performance of the MPVTW system were investigated by using the validated simulation model. The results show that the variations of these parameters have significant effects on thermal performance, but have little effect on electricity efficiency. The present study also found that when the distance (between the glass cover and PV module) was in the range of 12 mm -30 mm, the optimum values of total efficiency, thermal efficiency and electricity efficiency were 57.3%, 38.3% and 12.0%, respectively. (C) 2019 Elsevier B.V. All rights reserved.

This study proposed a new system with the photovoltaic (PV) panel installed in the middle of channel of the Trombe wall (TW) system, called as built-middle photovoltaic integrated Trombe wall (PVMTW), which can realize multiple functions of electricity generation, space heating and heat preservation. The experiment rig was built to study the temperature field of the PVMTW system in heating seasons, in Hefei. A mathematical model of the PVMTW system was developed and validated against experimental data. Using the validated model, the thermal performance of the PVMTW system was investigated by comparison with that of the classic Trombe wall. The results showed that in the daytime, the average thermal efficiency of the PVMTW system was 65.2% higher than that of the classic TW system. In terms of room air temperature and interior surface temperatures on the walls, the indoor thermal comfortable of the PVMTW system was almost the same as that of the classic TW system. The average predicted mean vote (PMV) for two rooms (room with the PVMTW system and room with the classic TW system) were 0.05 and -0.36, respectively. Additionally, the average electrical efficiency and average total efficiency achieved 0.120 and 0.585, respectively. (C) 2019 Published by Elsevier Ltd.

In order to satisfy seasonal energy demand and to decrease energy consumption of the building during the whole year, this paper presents a hybrid BIPV/T solar wall system. In winter, BIPV/Air mode is adopted to provide space heating and generate electricity for the building. During rest of the year, system is conducted in BIPV/Water mode to create hot water and electricity simultaneously. Firstly, the experiments are conducted under each mode respectively. Secondly, mathematical models are established and verified by the experimental results. Thirdly, parameter analyses are introduced to evaluate performance of the system under different situations. The main results are: (1) Daily experimental electrical output and efficiency are 0.12 kWh & 7.6% in summer and 0.65 kWh & 12.5% in winter. (2) Based on experimental results, water tank temperature is over 40 degrees C in summer, and the average temperature of the experimental room is 18.6 degrees Cin winter. (3) The optimal water flow velocity in summer is proved to be 0.04 L/s by parameter study. (4) The system is able to achieve passive space cooling in summer. (5) Based on simulation analysis, the system can provide space heating efficiently in winter. (C) 2019 Elsevier Ltd. All rights reserved.