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7.3.2: Parabolic Troughs and Fresnel Mirrors

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    It’s the least widespread CSP technology. As in the parabolic trough CSP technology, a long “linear” absorber is used in it. However, instead of a parabolic trough made of a single piece of appropriately profiled reflecting sheet, it uses an array of long flat light-reflecting “stripes”. Each stripe is inclined at a different angle, such that the beam of solar light reflected reflected by it is incident on the absorber.

    Showing how a Fresnel mirror is really a folded up set of pieces from the parabolic trough
    Figure \(\PageIndex{1}\): Solar light focused at en absorber in a parabolic trough (left image). If the trough shape is described by a y = ax2 parabola, all the reflected rays intersect at a single line located 1/4a above the trough bottom. Another way of focusing reflected sunrays on a linear a bsorber is to use the so-called “linear Fresnel mirror” consisting of a number of flat light-reflecting “stripes” (right image). Fresnel mirrors are less expensive than parabolic troughs, but the latter are more convenient to work with and therefore they are more often used (aop).

    A photograph of a large solar field in a CSP plant using linear Fresnel mirrors is shown in this Web page.

    When the Sun moves across the sky, each reflecting “stripe” should be rotated at a different angle. So, controlling the rotation is more complicated than in the case of a parabolic trough, but perhaps still much simpler than controlling the alignment of many thousands of heliostats in tower-type CSP plants. Anyway, the Fresnel mirror technology is not very popular – in the list of the largest CSP plants one can find only one such 125 MW plant operating in India, and one under construction in South Africa

    7.3.2: Parabolic Troughs and Fresnel Mirrors is shared under a CC BY 1.3 license and was authored, remixed, and/or curated by Tom Giebultowicz.

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