The concept described is an advanced holographic diffractive structure (HDS) for the control of light at the wavelength level. A stack of electrically controllable, liquid-crystal filled diffraction gratings would present a thin, lightweight, clear panel, that, when placed in contact with an aperture shall be able to concentrate sunlight very efficiently into a stable area in the center of a light guide or fiber optic device. It shall be possible to selectively bring into play only the grating appropriate for a particular sun angle and none other, by applying an electric field (creating a "smart grating"). A series of such concentrators will thus display active solar tracking without the disadvantages associated with moving mechanical parts. An example of a highly promising application of such a device is described within-holographic collection and transport of sunlight to a multi-story building's "core" area. Substituting sunlight for electric light will conserve a significant quantity of energy, particularly during peak load conditions, while at the same time delivering high quality illumination to the building's occupants. It is anticipated that the control device described herein, could provide formidable energy savings in the U.S. building sector by the year 2000.The potential commercial application as described by the awardee: Potential applications include, but are not limited to, peak load reductions (direct daylighting, load matching at the collecting end); photovoltaic optimization (wavelength selectivity, precision tracking); solar thermal (HDSs could be used in energy-efficient greenhouses and aquaculture systems to boost sunlight, reduce heat losses, and increase yields).
