experiment on the efficiency of the light shelves

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experiment on the efficiency of the light shelves

• Prof. Dr. Meltem YILMAZ

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Introduction

• As a day light intake system, light shelves can
  be seen as more economical than the other
  systems.
• Their features are, their simplicity, ease of
  applying to interior and exterior surfaces, ease
  of dissembling can prove this theory.
• However according to many sources, beside
  economical and practical features of the light
  shelves, their light intake factors can be
  limited with the positions of the buildings and
  windows, dimensions of the openings and the
  shelves.

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To research the efficiency of the light shelves,
single storey small shed has been built. Shed has
one door and one window which is lead to the
south. Dimensions of the shed are 240 cm x 500
cm x 220 cm and dimensions of the window are
90x100 cm.
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Construction of the demonstration shed
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Construction of the demonstration shed-2
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Also the distance between floor and window is 80
cm. After construction of the shed, a light shelf
has been applied to the window which is
adjustable and its dimensions are 50 x90 cm.
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• Measurements were taken in May in different hours
  as 1000 am and 1130 am due to determine effects
  of verticality and horizontality of the sunlight
  and try to provide correct results. Illuminance
  level has been measured with luxmetre and as
  intensity factor lux numbers were taken.
  Researches were studied with shelf and without
  shelf in different hours to search out the
  efficiency of light shelves. Also intensity of
  the daylight were measured on the floor from the
  different distances from 100 cm to 500 cm with
  light shelf and without light shelf in different
  hours.

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• Without Light Shelf
• at 10 oclock
• According to the test results without
  light shelf, at 10 oclock intensity level of the
  light from 100 cm to the window was measured as
  1284 lx. From 300 cm distance intensity of the
  light has been measured as 480 lx, and from 500
  cm distance, intensity of light has been measured
  as 179 lx.These measurements explain that,
  intensity of the light decreases seven times from
  100 cm to 500 cm without using light shelf.

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Without Light Shelfat 11.30 oclockTo
determine the vertical effect of sun light, also
at 1130 same tests have been done. From 100 cm
distance, 2010 lx has been measured. From 300 cm,
704 lx and from 500 cm 258 lx have been measured.
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• With Light Shelf
• At 10 oclock
• These, measurements have been retaken with the
  horizontal positioned light shelf. Dimension of
  the light shelf was 50x90 cm and it was made of
  steel with bright surfaces to take in and reflect
  more light. According to measurements with the
  light shelf At 10 oclock from 100 cm distance
  1969 lx has been measured, which was
  approximately 50 more than the (without light
  shelf) measurements. From 300 cm 662 lx and from
  500 cm 245 lx have been measured.

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With Light Shelfat 11.30 oclockTo determine
the vertical effect of sun light, also at 1130
same tests have been done. From 100 cm distance,
2310 lx has been measured. From 300 cm, 922 lx
and from 500 cm 345 lx have been measured.
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• In the tests that are made at 1130 oclock From
  the 100 cm distance, 2310 lx illuminance level
  has been measured( 2010 lx without light shelf).
  From the 300 cm distance 922 lx (without light
  shelf 704) and from the 500 cm distance 345 lx
  (without light shelf 258 lx) have been measured.
  Results show that although the vertical position
  of the sun, light shelf can take more daylight.

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Illuminance level with and without light shelf
Variation Factors at 10 oclock
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Illuminance level with and without light shelf
Variation Factors at 11.30 oclock
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• That means after 300 cm, effects of light shelf
  have been decreased. Reason of this, due to
  opening sizes, may be number of openings and
  dimension of the light shelf. These measurements
  show that although decreasing of illuminance
  level after the 300 cm, even a one window and a
  light shelf, intensity of the sun light seems
  enough to provide distinctive enlightenment.

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To sum up when the spaces and their openings
are designed with the optimum dimensions and
ratios, light shelves can be efficient for the
extra lightning. Test results show that
especially places where are close to the window
and light shelf, are taking more light than the
other places in the room. However, when the
narrow shape of the demonstration building and
small window are considered, especially after
300 cm distance, light intensity decreases.This
can be considered as a good result, because 300
cm is more than the half of the building, and 500
cm is the end part of the room.
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As a result, light shelves can be very economical
and effective daylight intake systems if the
position of the building leads to the correct sun
position and if the buildings and openings are
designed with optimum dimensions.
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• THANK YOU VERY MUCH