Scientists at University of Michigan develop innovative new solar panel design inspired by the Japanese art of kirigami
Affordable solar power for the average Joe – that is the dream. One of the most immovable objects to that dream has been finding a way to make solar panels tilt, or move, to follow the sun, as conventional, and immobile, arrays lose much of their potential energy when the movement of the sun across the sky means that the panel is no longer pointed at its energy source.
Moving the solar panels to track the sun has been shown to result in energy production increases of 20-40% (depending on the geographic location and whether the movement uses one or two axes) which brings solar energy far closer to the realms of commercial feasibility. However, the current methods of moving the panels are cumbersome and expensive, and are simply not practical, nor cost-effective, for general use. The additional weight and extra space required to account for structures needed to support that extra weight and resist wind loading mean that tracking solar arrays are only possible on ground-based or flat-roof installations. Pitched-roof installations, which account for ~85% of all solar roof systems, currently have no options for implementing tracking.
Enter Aaron Lamoureux and his colleagues at the University of Michigan, who believe that they may have the answer. Using the Japanese art of kirigami, a cousin of origami which involves cutting as well as folding, the team have developed a new system to provide an alternative to conventional tracking solar arrays. Kirigami techniques are already in use in the design of airbags, optical components, stowable spaceborne solar arrays, reprogrammable metamaterials and load-bearing metal structures.
In their proof-of-concept design, Lamoureux and his team have used similar design principles to show, for the first time, ‘simple, dynamic kirigami structures integrated with thin-film solar cells that enable highly efficient and macroscopically planar tracking as a function of uniaxial strain’. In their report published in Nature Communications earlier this month, the team claim that ‘for optimised systems, [they] show tracking to within ±10° of the predicted pointing vector, with total power generation approaching that of conventional single-axis tracking systems. Kirigami trackers are also show to be electrically and mechanically robust, with no appreciable decrease in performance after >300 cycles.’ The new panels also weigh roughly 1/10 of traditional tracking arrays, a major boon to the quest for affordable home-installations.
The design involves making specific kirigami cuts and folds in thin-film gallium arsenide solar cells to produce a contracting lattice structure which, when stretched, morphs to create a new shape, the individual strips of which do not cast shadows on each other, and the ‘waviness’ of which does not detract from performance, says Max Shtein, one of Lamoureux’s co-authors on the paper.
This approach allows the generation of more electricity using the same amount of semi-conducting material when compared with static models, almost to the same degree as conventional tracking panels. The team tested their panel at a solar panel farm in Arizona and found that it generated 36% more energy than a traditional, static array.
Of course, the design will require some energy input in order to stretch or otherwise manipulate the kirigami strips, but the energy required to stretch the shape is far less than that required to fully turn and tilt a conventional array.
“We think it has significant potential, and we’re actively pursuing realistic applications. It could ultimately reduce the cost of solar electricity,” Lamoureux says of the project.
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