Tunable prism based upon novel piezoelectric nanoparticle/sol-gel design used for active solar cells concentrators

Active solar concentrators attract significant interest in photovoltaic (PV) research activity since they can substantially reduce the area of PV cells while still collecting significant amount of solar energy via large aperture collecting optics. Solar concentrators include lenses or curved mirrors directing light from the sun into a smaller spatial spot falling on the PV cell. However, the main problem of active concentrators, severely limiting their practicality, is the high cost and low angular accuracy of sun tracking apparatuses. Specifically, tracking of the sun in existing concentrators is currently done through elaborate and expensive mechanical/optical systems, which exhibit lower performance over time and require energy input by themselves. In this paper we develop a novel active solar concentrator without any mechanical tracking. We aim to accomplish this goal through designing tunable prisms via novel chemical system comprising nanoparticles (NPs), specifically gold (Au) nanorods and silica NPs, embedded in semi-rigid transparent sol-gel matrixes, and placed within an electrical field. Changing the electrical field changes the partial distribution of the NPs and yields spatial gradient of refraction index, affecting the direction of the collected optical rays and allows their directing towards the PV cell according to the movement of the sun. In the paper we present the design and the realization of the first prototype as well as its preliminary experimental characterization.