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Researchers in Italy have developed a solar tracking photovoltaic system design for stadium roofs. The proposed approach is said to offer a strong structural response and high energy performance compared to systems based on fixed structures. Researchers from the University of Salerno and the University of Naples Federico II (Italy) have developed a new photovoltaic system design for small or medium-sized sports stadiums. The system is based on the combination of metal roof modules with lightweight, flexible photovoltaic panels, and is claimed to have a “remarkable” lightweight construction and stiffness properties. “The deployable structure used to activate the sun-tracking mechanism has been designed in such a way that it can be easily applied to existing stadiums,” Fernando Fraternali, corresponding author of the research, explained to pv magazine . “It can be applied to any stadium roof by appropriately connecting the bus cable to a support structure superimposed on the existing roof.” In the paper “ A tensegrity structure for a solar stadium roof with sun - tracking capability,” published in Thin-Walled Structures, the research team described the proposed design as a class 4 tensegrity system, in which the integrity of the structure depends on the balance of the tensioning elements. He also explained that the roof structure presented in the study is the so-called V-expander, which refers to the use of a rigid V-shaped strut in a tensegrity structure. “The original V-Expander was introduced by René Motro in his well-known textbook as a V-shaped system composed of eight bars arranged in two separate sets of four bars each, with equal lengths,” he further explained. “Our variant is a class 4 tensegrity structure composed of eight bars and seven cables.” The proposed photovoltaic roof is based on triangular metal roof modules with solar tracking photovoltaic panels. The movement that drives the tilt mechanism is activated by a winch placed in a suitable position and by adjusting the resting length of the bus cable, which allows movement with supposedly very low energy consumption. “The sun-tracking strategy uses a tensegrity drive technique, which is controlled by adjusting the resting length of a bus cable connected to struts,” the researchers explain. “This mechanism allows the lightweight roof tiles, covered with photovoltaic strips, to be optimally tilted to absorb maximum solar energy. The photovoltaic strips can be made from thin-film amorphous cells, organic photovoltaic cells or flexible photovoltaic panels. In addition, more standard photovoltaic panels could be used, provided their weight is accurately accounted for in the structural analysis.” The proposed method is said to increase the annual electrical energy production capacity of the solar roof by up to 54% compared to a fixed-pitch solar roof. “The locally variable solar tracking strategy is particularly effective during the winter months, achieving energy production increases of up to 80%,” the academics stress. “At rest, the lifting structure behaves as a lightweight tensegrity system.” The research group noted that the system could be further optimized by deploying its subunits at different tilt angles or by using dual-axis solar trackers. “Further improvements to the solar stadium design strategy could include the adoption of high-efficiency silicon solar cells, offering efficiencies of up to 27% – 28%, as well as the use of bifacial cells,” it concluded. “Furthermore, the tensegrity-stadium concept can be extended for large-scale stadiums.” |
