OPTISOL SOLAR CONCENTRATOR BASED ON NANOTECHNOLOGY
Shrink Nanotechnologies Inc., is a publicly traded nanotechnology company (OTCBB: INKN) involved in developing products and licensing opportunities in the medical diagnostics field, solar energy production, environmental sensors and biotechnology research and development tools businesses. The company’s renewable energy subsidiary, Shrink Solar, LLC, has recently formed its renewable energy team. This team includes academic and industry collaborators, including Michelle Khine, the scientific founder of the Shrink nano-technology platform; and Sayantani Ghosh, assistant professor, School of Natural Sciences, University of California.
The renewable energy team will focus on product development and optimization, all in an effort to achieve commercialization of the company’s OptiSol solar concentrator.
The OptiSol solar concentrator is a nanotechnology-based plastic solar concentrator. It falls into a class of devices known as luminescent solar concentrators. It is made from layers of the company’s NanoShrink material, nanocrystal “doped” glass and/or plexiglas (poly(methyl methacrylate) [PMMA]). The company has also worked with environmentally friendly corn-based plastics (polylactic acid [PLA]) and has integrated various types of quantum dot semiconductor nanoparticles into this layered structure. The manufacturing process differs slightly depending on the application. For example, “windows” require transparent panes whereas “siding” can be translucent or opaque. The company has also designed unique light trapping and light wave guiding mechanisms into the Optisol system.
Silicon converts the near infrared wavelengths into electricity more efficiently than the UV-Visible wavelengths. However, sunlight is mostly in the UV-Visible spectral region. Sunlight and silicon do not match perfectly, producing heat. The OptiSol solar concentrator makes them match: regular sunlight enters the concentrator and is shifted, emerging as silicon-optimal light. Certain iterations of the materials are transparent and hence there is possibility of light getting transmitted through the concentrator surface rather than getting reflected. There may be some reflections at the Photo Voltaic (PV) Cell- Concentrator interface but total internal reflection effectively traps and re-circulates the light within the device which indicates the ability of the device to absorb diffused light and off angle light to some degree. As a result, the loss of the total spectrum as heat or reflection is minimized to a great extent.
The device basically works on two principles namely concentration of the incident light onto a small amount of silicon and shifting of sunlight to illuminate the silicon cell with a better spectrum. The concentration of a large amount of incident light onto a large concentrator surface and then transferring it to a small photovoltaic (PV) cell proves to be an optimal solution since the cost of a plastic OptiSol solar concentrator is much less expensive than the cost of a silicon solar cell which drives down the system’s total cost. Silicon has much higher external quantum efficiency for near infrared (NIR) spectral region than for ultraviolet (UV)-visible region. Shifting visible sunlight to NIR allows the optical energy to be converted more efficiently without any changes to the PV cell itself. The OptiSol solar concentrator offers a number of advantages.
Concentrating solar power systems typically use mirrors, lenses and tracking devices to focus sunlight onto a small photovoltaic device. The OptiSol concentrator however does not employ any of these optical elements. It acts more like a fiberoptic “sheet,” trapping and guiding sunlight to a side-mounted PV cell. Since this design can be achieved using plastic rather than glass, the devices tend to be low-cost, lightweight and durable. While the other competing technologies use short-lived fluorescent dyes; and the materials used in this concentrator have very desirable life spans.
Talking to the Technical Insights team, Mark L. Baum, CEO of Shrink Nanotechnologies said, “One of the biggest problems we ran into was the degrading of our photovoltaics. If we did not solve this problem, the lifetime of our concentrator would have been measured in minutes. Thanks to the efforts of our research and development team, that lifetime has been extended almost indefinitely. While the concentrator itself is nearly indestructible under day-to-day conditions, the actual silicon PV cells are rather fragile. While we have resolved this issue, constantly breaking paper-thin panels was frustrating.”
The major application of the concentrator would be in functionalizing nearly every exterior surfaces of a home or building. The roof, windows, doors, siding, and so on, can all be transformed into power generators, with minimal aesthetic impact. Smaller scale applications would cater to consumer electronics, military devices and recreational markets. According to Baum, the largest market Nanotech Alert opportunity is in a roof-top application and it, like the siding applications, would be an opaque product. Their rooftop application can be completely integrated with the underlying ancillary systems required to make a traditional flat panel silicon PV system work. However, the company also envisions a day when the surfaces (windows and other plastic appendages) of a battery powered vehicle will be functionalized, allowing a commuter to re-fuel his or her vehicle with incident solar light during the work day.
Shrink is funding academic laboratories under a licensing and research agreement with the Regents of the University of California (UC). Through agreements with the Regents of the UC, the company holds exclusive license (for all fields of use) to the core patents related it’s solar concentrator technology. Shrink has also developed additional applications based on the original patent applications and is thus continuing to grow its own IP portfolio. In the near future, the company plans to build ultra low-cost, upgradable and flexible solar concentrators, and will integrate products based on this technology into clean buildings and other nonfunctional surfaces, dramatically impacting our dependence on non-renewable sources of energy.
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