Solar Glitter

Solar Glitter

Microsystem-enabled Photovoltaics

The key enabling technology for this approach to PV is the ability to create, through microsystems technology, very small solar cells made from high-quality crystalline silicon or gallium arsenide semiconductor materials. The cells are so small that, when released from their wafers, they take on the appearance of glitter. The cells are approximately 20 microns thick, 500 microns across, and composed of crystalline silicon. Efficiencies of nearly 15% have been demonstrated, exceeding 20% for single junction cells. Crystalline silicon and gallium arsenide make very good solar cells due to the high quality and performance of the material and semiconductor bandgap characteristics that are well matched to the solar spectrum.

However, these high quality materials are expensive. As much as 25% of the cost of a typical solar PV system comes from the silicon material alone. The Solar Glitter cells being manufactured at Sandia National Laboratories reduce the amount of silicon or gallium arsenide by at least a factor of ten. The small lateral dimensions of the cells provide additional benefits that are not possible with larger scale cells. For example, the image below shows a mechanical demonstration prototype of a flexible PV module comprised of the Solar Glitter cells. Traditional crystalline silicon solar cells are rigid and cannot provide this kind of flexible PV functionality. This improvement in performance in flexible PV modules would be of significant benefit to mobile or remote systems or sites, with particular benefits for the warfighter (even to the extent of a photovoltaic uniform). There are many additional benefits resulting from the small scale of the cells.

There is a built-in ability to improve the optical efficiency through the use of concentrating optics (i.e., microlenses). The systems are able to provide more robust system performance in shaded situations.

There is an enhanced ability to perform optical tracking (pointing the system toward the sun) within the module, thus reducing system costs such as racking, wiring, tracking, etc. High-voltage output can be derived directly from the module, thus reducing costs for wiring and/or DC/DC converters in large PV systems. A much better thermal performance of the system relative to conventional PVs improves the efficiency and extends cell lifetimes. Given the performance improvements and direct cost reductions, these advantages of “solar glitter” have the potential to enable solar power at a cost level competitive with fossil fuel grid power, thus allowing all the benefits of solar power (clean energy, no greenhouse gas emissions, abundant and distributed power, etc.) to be economically accessible.

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