When I use Brightdata with measured data , I use this equation;
( sky and solar )radiance= luminance/179
solar luminance is calculated from measured direct normal illuminance.
sky luminance is measured data.
Is this correct methods?
I think efficacy is not always 179.
But it seems to be unified into 179 in the RADIANCE system.
And ,one more question.
When accurate illuminance value in the room is required, should I take both ground plane and ground dome into consideration? Or,ground plane around the model only?
Thank you
Kouichi (?),
When I use Brightdata with measured data , I use this equation;
( sky and solar )radiance= luminance/179
solar luminance is calculated from measured direct normal illuminance.
sky luminance is measured data.
Is this correct methods?
I think efficacy is not always 179.
But!!it seems to be unified into 179 in the RADIANCE system.
The 179 lm/W value is Radiance's own 'internal' luminous efficacy.
It should not be confused with actual daylighting efficacies
which cover the range 50 to 150 lm/W (these are extremes, typical
values are around 100 to 120 lm/W).
And ,one more question.
When accurate illuminance value in the room is required, should I take
both ground plane and ground dome into consideration? Or,ground plane
around the model only?
A ground plane will usually be needed for high accuracy work. This is
becuase a (correctly specified) ground glow cannot account for the shading
of the ground plane by the building (see Fig 6.8 in Rendering with Radiance).
No harm in having a ground glow as well as a ground plane.
Both of your questions are addressed (with examples given) in the
newly reprinted Rendering with Radiance book. See earlier threads
for availability.
-John
···
-----------------------------------------------
Dr. John Mardaljevic
Senior Research Fellow
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)
[email protected]
http://www.iesd.dmu.ac.uk/~jm
Hi all,
in my opinion it is a question of the used spectrum. RADIANCE itself calculates completely within the visible spectrum. So the internal luminous
efficacy of 179 lm/W is from visible to visible spectrum.
The commonly used luminous efficacy is from the full spectrum (as e.g. measured by a pyranometer) to the visible. This efficacy strongly depend on the actual sky state (Blue sky about 90 lm/W, overcast sky about 130 lm/W).
If you use "gendaylit", the perez-sky luminous efficacy model is used to "transfer" full-spectrum data into the visible range and gives good results for the most sky situations.
Jan
John Mardaljevic wrote:
···
Kouichi (?),
When I use Brightdata with measured data , I use this equation;
( sky and solar )radiance= luminance/179
solar luminance is calculated from measured direct normal illuminance.
sky luminance is measured data.
Is this correct methods?
I think efficacy is not always 179.
But!!it seems to be unified into 179 in the RADIANCE system.
The 179 lm/W value is Radiance's own 'internal' luminous efficacy.
It should not be confused with actual daylighting efficacies
which cover the range 50 to 150 lm/W (these are extremes, typical
values are around 100 to 120 lm/W).
And ,one more question.
When accurate illuminance value in the room is required, should I take both ground plane and ground dome into consideration? Or,ground plane around the model only?
A ground plane will usually be needed for high accuracy work. This is
becuase a (correctly specified) ground glow cannot account for the shading
of the ground plane by the building (see Fig 6.8 in Rendering with Radiance).
No harm in having a ground glow as well as a ground plane.
Both of your questions are addressed (with examples given) in the
newly reprinted Rendering with Radiance book. See earlier threads
for availability.
-John
-----------------------------------------------
Dr. John Mardaljevic Senior Research Fellow
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972 +44 (0) 116 257 7981 (fax)
[email protected] http://www.iesd.dmu.ac.uk/~jm
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-------------------------------------------------------------------
o - > \ Jan Wienold
Fraunhofer Institute for Solar Energy Systems
SOLAR BUILDING DESIGN GROUP - DAYLIGHTING
Heidenhofstr. 2 79110 Freiburg
GERMANY
In office: Mo, Tue: 9:00-18:00
We-Fr: 14:30-18:30
Phone: ++49 - (0) 761 - 4588 -5- 133
Fax: ++49 - (0) 761 - 4588 -9- 133
Email: [email protected]
Internet:
http://www.ise.fraunhofer.de
I'm Kouichi.
I'm sorry that the mail was not correctly displayed.
Both of your questions are addressed (with examples given) in the
newly reprinted Rendering with Radiance book. See earlier threads
for availability.
Oh, that's great.
I am just going to wait to send the book now!
Regards,
Kouichi Kobayashi
Tokyo University of Science