September 05, 2018
Optical product design for solar power generation
Recently, Germany’s wind and solar farms surpassed lignite and hard coal as sources of electricity for the first time, potentially marking a tipping point in history for power generation. As Yogi Goswami, Director at the Clean Energy Research Center at University of South Florida shares on Forbes, “Solar energy is such a vast energy resource that it can be used for any of our everyday needs, including electrical power, heating and cooling, water heating, industrial process heat, cooking, transportation, fuel production, and even environmental clean-up. It comes to us as radiation which is pure energy (no mass associated with it), which is the highest form of energy and can be converted to many other forms for our everyday use. A tiny fraction of the solar energy that falls on the earth is sufficient to take care of all of the needs on the earth.”
Concentrated solar power
Similar to using a magnifying glass to start a fire, concentrated solar power systems help direct sunlight toward a small area using lenses or mirrors. Solar panels with solar concentrators need fewer solar cells, so the panels cost less to manufacture. Lower costs could help drive up use and contribute to a reduction in our global carbon footprint, reducing greenhouse gasses around the globe. Fresnel lenses are one type of solar concentrator. A Fresnel lens is a concave or convex lens that has been collapsed in the Z-direction. The profile is discontinuous and has grooves that minimize its thickness, but it is otherwise identical to a curved surface. Because the Fresnel lens is thin, there’s minimal light loss due to absorption at the expense of image quality. Fresnel lenses are used in lighthouse projectors, rear-projection televisions, and as solar concentrators, among several other uses.
Modeling a Fresnel lens in OpticStudio
There are several ideal and real Fresnel lens models available in OpticStudio’s sequential and non-sequential modes. For example, it includes:
Fresnel (sequential): The Fresnel surface is modeled as a flat surface. Once the ray has intercepted the plane surface, the ray reflects or refracts as if the surface had a shape described by an even asphere. The Fresnel surface can be used for Fresnel lenses with fine grooves (the groove depth is shallow compared to the aperture).
Generalized Fresnel (sequential): The Generalized Fresnel surface uses a polynomial aspheric substrate model, identical to the Even Aspheric surface. After the ray has intercepted the surface, the ray reflects or refracts as if the surface had a shape described by an extended polynomial. The Generalized Fresnel surface can be used to model faceted surfaces.
Fresnel 1 (non-sequential): In the Fresnel 1 object, the profile is made of radially flat faces. The endpoints of the faces follow the equation of the Even Asphere surface.
Tabulated Fresnel Radial (non-sequential): The Tabulated Fresnel Radial is a tabulated object based on YZ sag coordinates defined in a TOB file. A TOB file contains two columns of data: the first column represents the local Y coordinate, and the second column represents the local Z coordinate. A figure of revolution around the local Z axis is generated by replicating the YZ curve over a specific angular range. The radially symmetric faces that result are smooth.
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