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Chinese scientists have outlined a new system architecture for vacuum-integrated photovoltaic (VPV) curtain walls. They claim the new design can reduce buildings energy consumption and produce more surplus electricity.
A group of Chinese researchers have developed a new vacuum-integrated photovoltaic (VPV) curtain wall design that they claim can effectively combine photovoltaic power generation and building thermal insulation.
“For the first time, a multifunctional design method for photovoltaic curtain walls has been proposed, which aims to reconcile the demand for different functions of photovoltaic curtain walls, such as natural light, views and power generation,” he explains to pv magazine Jinqing Peng, lead author of the research. “We are now optimizing the height and PV coverage rate of each section, and after this study, we will cooperate with companies to produce the partitioned PV curtain wall.”
The researchers explained that photovoltaic curtain walls with high photovoltaic coverage can be beneficial for a building, as they can prevent large amounts of solar radiation from entering the building, thus avoiding overheating problems. On the contrary. VPV curtain walls with low PV coverage may have overheating problems, but can help the building require less energy for lighting and heating.
“Thus, the single-purpose optimal design of VPV curtain walls is unable to balance their restrictive and even contradictory functions,” they stated. “The main objective of this study is to balance the trade-offs between the different functions of the VPV curtain wall and improve its energy saving potential, while ensuring occupant comfort.”
The system consists of a photovoltaic laminated glass based on cadmium telluride (CdTe) solar cells, an air cavity and a vacuum glazing sheet. The scientists etched the solar cells into strips using lasers.
The system is also divided into daylight, view and spandrel sections according to different functions, and the PV coverage of each section needs to be determined separately. The daylight and view sections are designed to provide natural light and a visual connection to the outside, while the spandrel section is primarily intended for power generation. This allows the transmittances of each section to be modulated by adjusting the density of the photovoltaic cell strips.
The Chinese group simulated the performance of the VPV curtain using the Radiance and EnergPlus software and the order of preference by similarity to the ideal solution (TOPSIS) technique. They assumed that the system was implemented in a private office building facing south.
“It is assumed that this is the middle floor of a high-rise building with a glass curtain wall and dimensions of 2.7 m high, 4.0 m deep and 3.0 m wide,” the researchers stated. “The VPV curtain wall was equipped on the south façade with a large window-to-wall ratio of 86%.”
The simulation showed that the variation of the PV coverage of the daylight section has a great impact on the useful daylight illuminance (UDI) and the nuisance glare index (DGP). Annoying glare is a psychological sensation caused by high luminosity, and UDI refers to the amount of daylight useful to the occupants of a space.
Furthermore, the academics found that the optimal system configuration would require 20% PV coverage in the daylight section, 40% in the vision section, and 90% in the eardrum section. “The optimal VPV curtain wall, with photovoltaic coverage of 50%, 40% and 90% in the natural light, views and spandrel sections, achieved a 34.5% reduction in the glare index, an increase of 4.9 % in the UDI, an increase of 5.2% in the ratio of net zero energy hours (RNEH) and an increase of 112.59 kWh of surplus electricity,” they also explained.
The system is described in the study “ Multi-function partitioned design method for photovoltaic curtain wall integrated with vacuum glazing towards zero-energy buildings ”, published in Renewable Energy . The research group is made up of scientists from Shanghai Jiao Tong University and Hunan University (China).
“In terms of the cost of this system, the partitioned PV curtain wall only differs from the traditional PV curtain wall in the arrangement of the solar cell strips,” concludes Peng. “Consequently, there is no significant cost difference between the two designs, but the proposed partitioned photovoltaic curtain wall can reduce the buildings energy consumption and produce more surplus generation electricity.” |
