Experimental demonstration of high-concentration photovoltaics on a parabolic trough using tracking secondary optics

A new approach to high‐concentration photovoltaics (HCPV) based on a parabolic trough primary concentrator is presented. The design diverges from the standard HCPV arrangement of a two‐axis tracking point‐focus concentrator, and rather employs a simpler parabolic trough primary concentrator to reduce cost. To break the 2D limit of concentration, and bring the system into the realm of HCPV, the system employs an array of rotating secondary concentrators is arranged along the focal line of the parabolic trough. The resulting line‐to‐point (LTP) focus geometry allows the system to achieve a geometric concentration of 590×, yet still maintains the advantages of having a linear trough primary concentrator, namely manufacturability, economy, and scalability. A full‐scale prototype of the system was constructed in Biasca, Switzerland. During on‐sun tests a flux concentration of 364 suns was measured at the exit of the secondary concentrator, the highest reported concentration for any parabolic‐trough‐based system. Moreover, the system reached a peak efficiency of 20.2%, the highest measured solar‐to‐DC efficiency for a parabolic trough‐based solar collector. Long‐term performance is estimated by means of a coupled optical‐electrical model validated vis‐à‐vis the experimental results. This work serves as an experimental proof‐of‐concept for high‐concentration trough‐based collectors, thereby opening new avenues for reducing the cost of HCPV systems. Copyright © 2016 John Wiley & Sons, Ltd. High‐concentration on a parabolic trough? By arranging an array of rotating secondary optical elements (SOE) along the focal line of a parabolic trough, we show that the 2D limit of concentration of 215× can be considerably surpassed. We place an array of 3 J cells at the exit of each SOE, thus yielding the first trough‐based high‐concentration photovoltaic collector (Cg = 590×). From on‐sun testing of a full‐scale prototype, we report a solar‐to‐DC efficiency of 20.2%, the highest ever measured for a parabolic‐trough‐based PV system.