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FOCUS Technology Snapshot - Arizona State University's Solar-Concentrating Photovoltaic Mirror

The goal of the PVMirror project is to create a hybrid photovoltaic (PV) and concentrating solar thermal power (CSP) system that combines the high efficiency of a PV system with the energy storage benefits of a CSP system. The result will be a PVMirror power plant with an efficiency 50% higher than that of a conventional CSP plant for only 10% additional cost. This is achieved by splitting the broad solar spectrum and sending select wavelengths to PV cells while sending the rest to the CSP system.

A PVMirror looks like a conventional CSP trough mirror, but with an optical coating and PV cells lining the curved surfaces of the trough in place of the silver mirror coating. Incident near-infrared (NIR) light passes through the optical coating to the silicon PV cells behind, where it is absorbed and converted directly to electricity with >40% efficiency. The shorter visible wavelengths and longer infrared (IR) wavelengths—which cannot be efficiently used by silicon PV cells—are reflected by the coating. Because the coating is conformal to the curved glass trough (which tracks the sun from East to West throughout the day), this light is concentrated at the trough’s line focus where a black tube (thermal absorber) is placed. The heat that is transferred to oil passed through this tube powers a steam turbine to generate electricity, or it is stored until the sun sets for nighttime electricity generation.

The aim of this project is the development of silicon PV cells and optical coatings that are optimized for use in PVMirrors; the lamination of the curved glass, optical coating, and PV cells into PVMirror prototypes; and a techno-economic analysis of these prototypes to demonstrate the viability of PVMirrors in the solar energy market.