Page 259 - Alternative Energy Systems in Building Design
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CONCENTRATOR SOLAR TECHNOLOGIES    235


                       Emission reduction Emissions benefits of CSP technologies depend on many
                       factors, including whether they have their own storage capacity or are hybridized with
                       other electricity- or heat-producing technologies. CSP technologies with storage produce
                       zero emissions, and hybrid technologies can reduce emissions by 50 percent or more.


                       PASSIVE PARABOLIC HEATING TECHNOLOGIES
                       In this technology, a large field of parabolic systems that are secured on a single-axis
                       solar-tracking support is installed in a modular parallel-row configuration aligned in a
                       north-south horizontal direction. Each of the solar parabolic collectors tracks the
                       movement of the sun from east to west during daytime hours and focuses the sun’s
                       rays to linear receiver tubing that circulates a heat-transfer fluid (HTF). The HTF, in
                       turn, passes through a series of heat-exchanger chambers where the heat is transferred
                       as superheated vapor that drives steam turbines. After propelling the turbine, the spent
                       steam is condensed and returned to the heat exchanger via condensate pumps. Figure 6.9
                       is a photograph of a parabolic heater installation.
                         At present, the technology has been applied successfully in thermal electric power–
                       generation. A 354-MW solar electric power–generation plant installed in 1984 in the
                       California Mojave Desert has been in operation with remarkable success.


                       SOLAR TOWER TECHNOLOGIES
                       Another use of CSP technology that generates electric power from the sun is a con-
                       struction that focuses concentrated solar radiation on a tower-mounted heat exchanger.
                       The system is basically configured from thousands of sun-tracking mirrors, commonly




























                        Figure 6.9  Passive parabolic concentrator installation. Courtesy of Solargenix.
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