Nature-inspired smart solar concentrators by 4D printing

Currently, solar concentrators, whether in solar PV or solar thermal applications are designed and utilized as a fixed shape such as elliptic, parabolic, V-shape, hyperbolic, and multi-stage forms. Here, we are inspired by diurnal and nocturnal flowers and their differences and propose a smart solar concentrator that can increase the overall optical efficiency more than 25% compared with its non-smart counterparts. We introduce the concept of smart solar concentrators inspired by nature and enabled by 4D printing and illustrate its necessity and advantages. We found that most of the diurnal flowers have parabolic and most of the nocturnal flowers have hyperbolic petals. Our proposed multi-functional concentrator has a parabolic shape for a portion of the day that parabola dominates all the other shapes in terms of the optical efficiency, then it can reversibly change its shape to hyperbola for another portion of the day that the hyperbola beats all the other geometries. By using this design, the optical efficiency trend will move from peak-and-valley form toward constant-at-peak format, resulting in overall efficiency improvement. The proposed biomimetic structure is an example of smart origami. It is simple, low-mass, and demonstrates the desired shape-shifting without reliance on cumbersome and expensive electromechanical systems. (C) 2018 Elsevier Ltd. All rights reserved.