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                       PASSIVE SOLAR HEATING


                       TECHNOLOGIES














                       This chapter will review the basic principles of passive solar energy and its applications.
                       The term passive implies that solar power energy is harvested with the direct exposure
                       of fluids, such as water or a fluid medium, that absorb the heat energy. Subsequently, the
                       harvested energy is converted to steam or vapor, which, in turn, is used to drive turbines
                       or provide evaporative energy in refrigerating and cooling equipment. Figure 6.1 shows
                       the historical use of passive solar energy to power a printing press.
                         Solar power is the sun’s energy, without which life as we know it on our planet would
                       cease to exist. Solar energy has been known and used by humankind throughout the
                       ages. As we all know, solar rays concentrated by a magnifying glass can provide intense
                       heat energy that can burn wood or heat water to its boiling point. As discussed later,
                       recent technological developments of this simple principle are currently being used to
                       harness solar energy and provide an abundance of electric power. Historically, the prin-
                       ciple of heating water to its boiling point was well known by the French, who in 1888
                       used solar power to drive printing machinery.
                         Appendix C provides a detailed solar power historical timeline.




                       Passive Solar Water Heating


                       The simplest method of harvesting energy is to expose fluid-filled pipes to the sun’s
                       rays. Modern passive solar panels, which heat water for pools and general household
                       use, are constructed from a combination of magnifying glasses and fluid-filled pipes.
                       Figure 6.2 illustrates the operation of a passive solar water-heating panel. In some
                       instances, pipes carry special heat-absorbing fluids, such as a bromide solution, that
                       heat up quite rapidly. In other instances, water is heated and circulated by small pumps.
                       In most instances, pipes are painted black and are laid on a silver-colored reflective
                       base that further concentrates the solar energy. Another purpose of silver backboards

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