Flexible Spectrum Splitting Holographic Concentrators

The DOE has undertaken a new Solar America Initiative (SAI) to accelerate the development of photovoltaic systems, with the goal of making solar energy cost-competitive with other forms of renewable electricity by the year 2015. In support of this goal, this project will demonstrate a low-cost flexible Spectrum Splitting Holographic Concentrator (SSHOC) that focuses light onto solar cells with high efficiency, thereby increasing the output of existing photovoltaic (PV) systems. The SSHOC, which is based on four thin film holographic optical elements that are dispersion- and aberration-corrected, is easily manufactured, has 99 percent diffraction efficiency, is lightweight, and has low-cost. Phase I demonstrated feasibility by theoretical analysis and computer modeling, and by fabricating a compact experimental prototype. Spectral characteristics of the prototype were investigated through a series of laboratory experiments, performance tests, and the analysis of the results. A number of advantages over existing techniques and approaches were demonstrated: (1) highly stable spectral characteristics of volume holographic multilayer¿s, (2) compact packaging into a single module for all wavelengths, and (3) tunable bandwidths over a spectral range from visible to near IR. Phase II will complete the SSHOC development and optimize the holographic optical elements so that they will be mass producible and superior to state-of-the-art technologies in terms of both performance and cost. Commercial Applications and Other Benefits as described by the awardee: The flexible SSHOC technology should primarily benefit concentrator PV systems for use with multi-junction solar cells, providing mass reduction, simplified deployment, and increased efficiency and power output. Because it is scalable, the system can be adapted to a variety of applications, from large solar collectors in space to solar tiles for residential homes. The technology also find should find use in a wide range of other applications such as optical imaging systems, optical displays, virtual image displays, and optical instrumentation.