Publications

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Sandia has developed an optical design for wearable binoculars utilizing freeform surfaces and switchable mirrors. The goals of the effort included a design lightweight enough to be worn by the user while providing a useful field of view and magnification as well as non-mechanical switching between normal and zoomed vision. Sandia's approach is a four mirror, off-axis system taking advantage of the weight savings and chromatic performance of a reflective system. The system incorporates an electrochromic mirror on the final surface before the eye allowing the user to switch between viewing modes. Results from a prototype of a monocular version with 6.6x magnification will be presented. The individual mirrors, including three off-axis aspheres and one true freeform, were fabricated using a diamond-turning based process. A slow-slide servo process was used for the freeform element. Surface roughness and form measurement of the freeform mirror will be presented as well as the expected impact on performance. The alignment and assembly procedure will be reviewed as well as the measured optical performance of the prototype. In parallel to the optical design work, development of an electrochromic mirror has provided a working device with faster switching than current state of the art. Switchable absorbers have been demonstrated with switching times less than 0.5 seconds. The deposition process and characterization of these devices will be presented. Finally, details of an updated optical design with additional freeform surfaces will be presented as well as plans for integrating the electrochromic mirror into the system. © 2013 SPIE.

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Microsystems Enabled Photovoltaics (MEPV) is a relatively new field that uses microsystems tools and manufacturing techniques familiar to the semiconductor industry to produce microscale photovoltaic cells. The miniaturization of these PV cells creates new possibilities in system designs that may be able to achieve the US Department of Energy (DOE) price target of $1/Wp by 2020 for utility-scale electricity generation. In this article, we introduce analytical tools and techniques to estimate the costs associated with a concentrating photovoltaic system that uses microscale photovoltaic cells and miniaturized optics. The overall model comprises the component costs associated with the PV cells, concentrating optics, balance of systems, installation, and operation. Estimates include profit margin and are discussed in the context of current and projected prices for non-concentrating and concentrating photovoltaics. Our analysis indicates that cells with a width of between 100 and 300 μm will minimize the module costs of the initial design within the range of concentration ratios considered. To achieve the DOE price target of $1/Wp by 2020, module efficiencies over 35% will likely be necessary. © 2013 IEEE.

Microsystem technologies have the potential to significantly improve the performance, reduce the cost, and extend the capabilities of solar power systems. These benefits are possible due to a number of significant beneficial scaling effects within solar cells, modules, and systems that are manifested as the size of solar cells decrease to the sub-millimeter range. To exploit these benefits, we are using advanced fabrication techniques to create solar cells from a variety of compound semiconductors and silicon that have lateral dimensions of 250 - 1000 μm and are 1 - 20 μm thick. These fabrication techniques come out of relatively mature microsystem technologies such as integrated circuits (IC) and microelectromechanical systems (MEMS) which provide added supply chain and scale-up benefits compared to even incumbent PV technologies. © The Electrochemical Society.

Microsystems Enabled Photovoltaics (MEPV) is a relatively new field that uses microsystems tools and manufacturing techniques familiar to the semiconductor industry to produce microscale photovoltaic cells. The miniaturization of these PV cells creates new possibilities in system designs that may be able to achieve the US Department of Energy (DOE) price target of $1/Wp by 2020 for utility-scale electricity generation. In this article, we introduce analytical tools and techniques to estimate the costs associated with a concentrating photovoltaic system that uses microscale photovoltaic cells and miniaturized optics. The overall model comprises the component costs associated with the PV cells, concentrating optics, balance of systems, installation, and operation. Estimates include profit margin and are discussed in the context of current and projected prices for non-concentrating and concentrating photovoltaics. Our analysis indicates that cells with a width of between 100 and 300 μm will minimize the module costs of the initial design within the range of concentration ratios considered. To achieve the DOE price target of $1/Wp by 2020, module efficiencies over 35% will likely be necessary. © 2013 IEEE.

A 100X magnification, ±3° field of view micro-concentrating optical array has been developed with better than 90% transmission for a microsystems-enabled photovoltaic (MEPV) prototype module using 250 μm diameter multi-junction "stacked" PV cells. Renewable Energy and the Environment Congress. © 2013.

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