Page 255 - Alternative Energy Systems in Building Design
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PASSIVE SOLAR WATER HEATING  231


                         If the pool is shaded, you need to multiply the sizing factor by the following figure:

                         25 percent shaded    1

                         50 percent shaded    1.25
                         75 percent shaded    1.50
                         100 percent shaded   1.75

                         As a general rule of thumb, if there is a screen enclosure, multiply the factor by
                       1.25. If the pool is indoors, multiply the sizing factor by 2.00.
                         In the northern states, the best collector angle is the latitude minus 10. This changes
                       gradually as you move south, until it reaches the latitude plus 10 in south Florida. For
                       each 10-degree variance from the optimal angle, multiply the sizing factor by the
                       following figure:





                        DEVIATION              FIGURE
                        <10 degree              1.05
                        20 degree               1.10
                        30 degree               1.20





                       As a general rule of thumb, if collectors are laid flat, multiply the sizing factor by 1.10.
                         For the collector area, use the following:

                         HC-50                50

                         HC-40                40
                         HC-30                30


                       Example This example illustrates sizing-factor determination and the number of
                       collectors needed on a partially shaded flat roof for a 15 ft × 30 ft rectangular pool.

                         Langley’s for coldest month of swimming is December: 0.55.

                         Collectors are going to face south.
                         Pool shaded 25 percent (multiply by): 1.1.
                         Collectors are going to go on a flat roof (multiply): 1.1.

                         Sizing factor: 0.67.
                         Surface area of the pool: 450 ft. 2
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