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Chinese scientists have built photovoltaic blinds capable of regulating the thermal load, the penetration of natural light and the generation of energy in tall buildings with glass facades. Their creators claim that the blinds offer superior architectural aesthetics and notable energy-saving potential.Chinese researchers have developed a new dynamic vertical integrated photovoltaic building envelope (dvPVBE) system for high-rise buildings with glazed facades.
The novelty of the system lies in its flexibility, with slat angles and blind positions that respond to weather conditions. “Recently, very dynamic PVBE systems that are sensitive to weather conditions have been studied to improve the energy efficiency of buildings,” the researchers explain. “However, the relatively complex structures are not suitable for high-rise buildings due to their weak windbreak characteristics, which prevent their large-scale application in cities. “Consequently, the development of simple, flexible and intelligent photovoltaic shading devices continues to present significant challenges.”
To solve these problems, the scientists designed the proposed system as an airtight outer layer of the windows. In a prototype they made, the frame structure and slats of the blind were made of aluminum alloy, and the solar cells were integrated into the slats. The slats were controlled by a motor, hidden in an upper structure of the frame.
“Unlike traditional static exterior blinds, the dvPVBE slats can stop at any frame height and rotate between 0 and 90 degrees by precisely controlling the motor stroke,” they explain. “The blinds can be partially or fully deployed.”
The dvPVBE can be controlled manually by building occupants or automatically using three automatic control strategies, which the group called Power Generation Priority (PGP), Daylighting Priority (NDP), and Energy Saving Priority (ESP). In each of them, the angle of the slats and the position of the blind are controlled by a series of parameters, such as incident solar radiation, room occupancy, interior lighting and the consumption and generation of electrical energy in real time. The position of the blind refers to the distance between the upper frame and the lower slat.
The PGP and ESP control strategies were further investigated in a computer simulation. A 24-story office building in Beijing, China, was designed for the tasks, without additional high-rise buildings around it. In that building, a representative room of 5 × 5 × 3 m was simulated located on the south-facing façade, with a window-to-wall ratio of 70%. Heating, ventilation and air conditioning (HVAC) temperatures were set below 26°C in summer and above 18°C ??in winter.
Including a start-up period, during weekdays the system was operational from 7:00 a.m. to 6:00 p.m. The photovoltaic system of the slats was simulated with 26 monocrystalline silicon cells per slat and 24 slats per window. The cells were assumed to be from the Chinese manufacturer JinkoSolar, with an efficiency of 21.32%. The angles of the slats could vary in 5 degree increments. Four typical days around the spring equinox, summer solstice, autumn equinox and winter solstice were selected for analysis.
“For the dvPVBE control strategies, the PGP strategy was used during non-working hours and the ESP strategy during working hours,” explains the researcher. “To further demonstrate the feasibility of dvPVBE in improving the energy efficiency of buildings and to make a fair comparison with static photovoltaic blinds, the simulation mainly focused on evaluating the influence of adjustable slat angles on energy performance. ”.
The simulation showed that the dvPVBE system had a higher energy performance than static PVBE throughout the year. The dvPVBE covered 131% of the annual energy demand of the office room. Compared to the static system, the net energy production increased by at least 226%.
“During most of the day throughout the year in Beijing, slat angles of 45° to 60° are recommended to balance the use of natural light and solar energy,” the academic group emphasizes. “In the early morning, large slat angles are recommended to allow sufficient penetration of natural light and reduce the lighting load, especially in winter.”
The academics presented the novel concept in the study “ A New Dynamic and Vertical Photovoltaic Integrated Building Envelope for High-Rise Glaze-Facade Buildings ,” published in Engineering . The group consisted of scientists from Chinese Shenzhen University, Tsinghua University, Songshan Lake Materials Laboratory, Chinese Academy of Sciences, Hunan University, State Key Laboratory of Intelligent Geotechnics and Tunneling, and the Ministry of Education. . |
