One-axis tracking holographic planar concentrator systems

A design methodology for low-concentration ratio holographic solar concentrators with one-axis tracking is investigated. This methodology maximizes the energy collected by cascaded holographic gratings and reduces diffracted beam cross talk between gratings. Several types of transmission gratings, optimized to work with single-axis tracking systems, are used in a cascaded configuration to concentrate a large fraction of the useable solar spectrum on the surface of photovoltaic cells. A model is developed that determines the energy yield of the holographic planar concentrator (HPC). Good agreement is found between simulation and measurement of a prototype system. Simulation of an optimized HPC design shows that 80% optical efficiency at 2X geometric concentration ratio is possible. The acceptance angle in the nontracking direction is ±65 deg, and a ±16-deg tracking tolerance is sufficient to maintain 80% of the maximum optical efficiency. Simulation also shows that the single-axis tracking HPC system has a 43.8% increase in energy yield compared to a nontracking holographic solar concentrator.