[Radiance-daysim] Radiance-daysim Digest, Vol 26, Issue 2

Thu Aug 11 04:06:46 PDT 2016

Hi Abigail,

-for the solar transmissivity you can use the same equation.

-the pts-file does not contain the information about the sensor type. If 
you want to change that manually, you have to do that in the header 
file. Syntax please see here: 
http://daysim.ning.com/page/keyword-output-units . If you have hundreds 
of points, I recommend to write a script generating for you this entry 
in the header-file.

-I haven't used the new version of DIVA yet, so maybe someone else can 
answer this question more detailed. I know you can go two approaches, 
either you define a node in W/m*m and run an annual simulation with 
daysim OR you run an irradiation map with /gencumulativesky /,but I'm 
not sure where to invoke the latter one in the new version.

good luck!
Jan/
/

On 11/08/16 12:09, Abigail Chi wrote:
>
> Hi Jan
>
> To compute trasnmissivity (tn) from transmittance (Tn), I should use:
>          tn = (sqrt(.8402528435+.0072522239*Tn*Tn)-.9166530661)/.0036261119/Tn
> But, how can I compute the solar transmissivity from the solar 
> transmittance?
>
>
> Besides, can you help me with the following:
> - What is the way in Daysim to customize all sensor points in the 
> file  *.pts as irradiance sensors? This last in order to avoid 
> customizing all sensors, one by one, in the sensor type column of the 
> Daysim  interface.
>
> - I am new in Diva-for-Rhino, but I have seen that  it can 
> calculate annual irradiation at node locations (radiation maps-grid 
> based). Is this equivalent to the calculation of the solar irradiation 
> in Daysim?
>
> Many thanks
>
>     ------------------------------
>
>     Message: 2
>     Date: Thu, 11 Aug 2016 11:49:22 +0200
>     From: Jan Wienold <jan.wienold at epfl.ch <mailto:jan.wienold at epfl.ch>>
>     To: DAYSIM discussion <radiance-daysim at radiance-online.org
>     <mailto:radiance-daysim at radiance-online.org>>
>     Subject: Re: [Radiance-daysim] Radiance-daysim Digest, Vol 26, Issue 1
>     Message-ID: <ab89d49d-385d-a1fd-9687-b4e4929e3755 at epfl.ch
>     <mailto:ab89d49d-385d-a1fd-9687-b4e4929e3755 at epfl.ch>>
>     Content-Type: text/plain; charset="windows-1252"; Format="flowed"
>
>     Radiance and Daysim do internally not raytrace spectrally - there are
>     calculating simply in channels (RGB for Radiance, Daysim just
>     one). That
>     means:what you put in you will get out :
>
>     If you use a weather file with solar spectrum AND your material
>     properties are valid for that range (that means using solar
>     transmittance, solar reflectance) then you also get solar
>     irradiance as
>     output.
>
>     That means for your last question: Yes, you should insert the "solar
>     transmissivity" (must be calculated from the solar transmittance).
>     Don't
>     forget to use also solar reflectance values for all your surfaces.
>     Usually they are very similar to the visible, but there are
>     exceptions.
>
>     But please consider, that Radiance (and daysim) are raytracers!
>     They do
>     not consider any change in wavelength for a ray. That means they
>     do NOT
>     consider the heating up of a surface when it is absorbing
>     radiation and
>     emitting it in the IR.
>
>     That's why you CANNOT calculate the "real" SHGC of a window
>     system. You
>     can just calculate the solar transmittance. Depending on your glazing
>     system the difference between the SHGC and the solar transmittance
>     could
>     significant (I guess more than 40% is possible in general,
>     typically the
>     difference for a normal glazing is in a range of 10-20%)!
>
>     E.g. if you check  a typical glazing from Interpane (Tau_vis=0.76,
>     Tau_solar=0.48, SHGC=0.55, see here:
>     http://www.interpane.net/interpane2013/teweint.php?lang=de&site=10331.html
>     <http://www.interpane.net/interpane2013/teweint.php?lang=de&site=10331.html>),
>     the difference is 13%. For a combination of Planilux/Planitherm of St.
>     Gobain I calculated with Window 7 (LBNL software) Tau_vis 0.75,
>     Tau_solar=0.48 and SHGC of 0.59 (19% difference).
>
>     Jan
>
>
>
>     On 11/08/16 10:17, Abigail Chi wrote:
>     > Hi Christoph and many thanks for your answer. I have the following
>     > queries.
>     >
>     > - I choose a material (in this case a glass) and specify its
>     > transmissivity as follows:
>     >       mod glass id
>     >          0
>     >          0
>     >          3 rtn gtn btn
>     > This defines the way "visible light" is transmitted through the
>     glass.
>     > I think this is useful when I use illuminance sensors.
>     > But, if I use the irradiance sensors, do I need to specify the solar
>     > transmittance of the glass instead of the visible transmittance?
>     >
>     > - What is the way in Daysim to customize all sensor points in
>     the file
>     > *.pts as irradiance sensors? This last in order to avoid customizing
>     > all sensors, one by one, in the sensor type column of the Daysim
>     > interface.
>     >
>     > - I am new in Diva-for-Rhino, but I have seen that it can calculate
>     > annual irradiation at node locations (radiation maps-grid based). Is
>     > this equivalent to the calculation of the solar irradiation in
>     Daysim?
>     >
>     > Thanks in advance.
>     > Abigail
>
>
>
>
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-- 
Dr.-Ing.  Jan Wienold
Ecole Polytechnique Fédérale de Lausanne (EPFL)
EPFL ENAC IA LIPID

http://people.epfl.ch/jan.wienold
LE 1 111 (Office)
Phone    +41 21 69 30849

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