SOLARTRAN HEAT REJECTING SKYLIGHTS AND ATRIUMS
A skylight can be made heat rejecting by adding light redirecting panels as in Fig 1 below. High elevation sunlight is redirected from one panel across to the other then out of the skylight thereby reducing the relative transmission or shading coefficient, SC, of the skylight well below 1, see Fig 2. Mid elevation sunlight passes through without redirection and the transmission is about the same as a conventional skylight, SC ~ 1. Low elevation sunlight is transmitted much more effectively with the relative transmission or shading coefficient much greater than 1 and typically 3 or more at low sun elevations.
FIG 1. Illustrating redirection of sunlight by laser cut panels. FIG 2. Typical shading coefficient, SC, of an angle selective skylight vs time.
Waterford State School. Heat rejecting panels allow skylights to be used in summer in warm climates. An example is this classroom in Brisbane, Latitude 27. With heavy shading necessary to reduce radiant heat input through the windows the pyramid style angle selective skylights shown provide an effective means to naturally illuminate classrooms without the excessive heat gain that conventional skylights transfer during the middle of the day.
The Dinosaur Trackway Museum in Central Australia was designed to operate without air conditioning. To minimize radiant heat gain while providing natural illumination pyramid style angle selective skylights similar to those on the school classroom above were used. These skylights provide the base lighting of the building with electric spot lights near ground level providing shadow relief of the dinosaur tracks.
RTA Building, Herschel St, Brisbane. This building has a large three storey atrium that accommodates a staircase and provides natural illumination. The gable style atrium cover has a second internal glazing of laser cut panels to provide radiant heat rejection in summer. This view looks up towards the peak of the gable at noon in summer when the sun is directly overhead. Each panel, approx. 2m x 1m, contains three narrow clear regions that transmit sunlight while the major laser cut regions of the panels reject sunlight back to the outside. At noon the shading coefficient is reduced to about 20% with 80% of the potential heat input rejected.
LIGHT SPREADING SKYLIGHTS.
Angle selective skylights in inverted form provide for the distribution of light from skylights widely over the interior of the building as illustrated below..
The Brisbane Herbarium, (above). This building on completion was entirely filled with high filing cabinets. To naturally illuminate the building a large light spreading skylight was used to redirect light over the top of the cabinets and onto the surrounding ceiling. Light diffusely reflected from the ceiling illuminates the areas between the filing cabinets.
Norman Park State School, Brisbane. The photograph to the far left shows the view looking up through a dual-effect angle selective skylight. A heat rejecting skylight may be seen at the roof level with a light spreading skylight below at the ceiling level. The photograph to the near left shows a interior view of the skylight. Note that the architect flared the ceiling for mainly aesthetic reasons.
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