Sandia National Laboratories will this month start researching using a solar cell the size of a grain of sand to produce electricity his month.
Called microsystems-enabled photovoltaic (MEPV) systems, the cells have an estimated efficiency of up to 20 percent. Nielson says they could cost $1.80 per watt-peak (a measure of how many watts a panel produces when sunlight is at its peak). The current cost for a PV system is about $4 per watt-peak for a utility-scale system.
The project will involve putting thousands of them onto a one-foot square array. The cells were developed in 2009, but it took some time to find the right application, improve the consistency of performance and raise the power efficiency, said Greg Nielson, team leader on the project.
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Ordinary solar cells are made in 6-inch square blocks. But that size, although not huge, still presents a problem when the panel becomes partially shaded. When a solar cell gets partially shaded, it doesn’t just generate less power, it stops working completely. A solar panel made of thousands of independent tiny cells would be less affected by shade.
And being so tiny, the cells don’t have to be mounted on a stiff, block-like substrate. They could be mounted on flexible surfaces or even clothing. Imagine plugging into a jacket to extend the battery life of a smart phone. The tiny cells would also use much less silicon to make a cell of the same size, and they can be made from silicon wafers of any dimensions. Coupled with their efficiency it cuts the cost of each watt per gram of silicon. The manufacturing process also doesn’t require radically new techniques; the methods are used in current fabrication plants for making micro-electromechanical systems (MEMS).
Power from the cells could also be boosted using small lenses to concentrate the sun’s light, making more photons available to pump out electricity. Smaller lenses are often cheaper to mass-produce than larger ones.
Nielsen says it will still be a few years before power modules that can be used for a building. (He estimates about seven years, though prototypes would be done much sooner than that). In the meantime there are other pieces of solar photovoltaic technology that could be adapted to the tiny cells. Using other wavelengths of light, for example. There is also still a lot of room to improve the design and efficiency of manufacture, and Sandia is working with several corporate and university partners to explore that.
Image: Sandia National Laboratories