Radiance-daysim Digest, Vol 26, Issue 1

radiance-daysim
1

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

···

On Wed, Aug 10, 2016 at 9:00 PM, < [email protected]> wrote:

Send Radiance-daysim mailing list submissions to
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When replying, please edit your Subject line so it is more specific
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Today's Topics:

   1. Calculation of the solar irradiation with Daysim (Abigail Chi)
   2. Re: Calculation of the solar irradiation with Daysim
      (Christoph Reinhart)

----------------------------------------------------------------------

Message: 1
Date: Wed, 10 Aug 2016 15:32:22 +0200
From: Abigail Chi <[email protected]>
To: [email protected]
Subject: [Radiance-daysim] Calculation of the solar irradiation with
        Daysim
Message-ID:
        <CAPSjnYi9cLLYiCAJ+_UzYcNFY3xcShUxVr=VbbbLqRxs2cOf
[email protected]>
Content-Type: text/plain; charset="utf-8"

Dear all

I am working on different daylight simulations with Daysim 3.0. My interest
is to calculate the solar irradiation but I have some queries:
- What solar irradiance spectrum is measured if I use irradiance sensors
instead of illuminance sensors?
- Could Daysim take into account the SHGC of different window glazing?
- Is it possible that the glazing system was opaque to the long-wave
radiation?

Thanks in advance

Abigail
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Message: 2
Date: Wed, 10 Aug 2016 17:36:25 +0000
From: Christoph Reinhart <[email protected]>
To: DAYSIM discussion <[email protected]>
Subject: Re: [Radiance-daysim] Calculation of the solar irradiation
        with Daysim
Message-ID:
        <1B23446CBF250648A2FC775DE3FE7E80FF461BC5@OC11expo28.
exchange.mit.edu>
Content-Type: text/plain; charset="utf-8"

- What solar irradiance spectrum is measured if I use irradiance sensors
instead of illuminance sensors?
The Daysim program ds_illum has a luminous efficacy model according ot
Perez built in that converts irradiance into illuminances if you choose the
latter type of output. Otherwise, DAYSIM just uses the direct and diffuse
irradiances for an epw weather file. Typically those should have been
measured with a pyranometer, i.e. they should correspond ot the full
visible and IR spectrum.

- Could Daysim take into account the SHGC of different window glazing?
If you use the irradiance output the window transmittance should indeed
correspond to the window?s SHGC.

- Is it possible that the glazing system was opaque to the long-wave
radiation?
I am unsure what you mean here. DAYSIM/RADIANCE use simplified RGB (3
channel) or often effectively 1 channel simulations and do nto support a
full spectral analysis. I believe that Mehlika Inanici is working on a
spectral version of RADIANCE.

Best,

Christoph

From: Abigail Chi [mailto:[email protected]]
Sent: Wednesday, August 10, 2016 9:32 AM
To: [email protected]
Subject: [Radiance-daysim] Calculation of the solar irradiation with Daysim

Dear all

I am working on different daylight simulations with Daysim 3.0. My
interest is to calculate the solar irradiation but I have some queries:
- What solar irradiance spectrum is measured if I use irradiance sensors
instead of illuminance sensors?
- Could Daysim take into account the SHGC of different window glazing?
- Is it possible that the glazing system was opaque to the long-wave
radiation?

Thanks in advance

Abigail

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End of Radiance-daysim Digest, Vol 26, Issue 1
**********************************************

2

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), 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
         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

On Wed, Aug 10, 2016 at 9:00 PM, > <[email protected] > <mailto:[email protected]>> wrote:

    Send Radiance-daysim mailing list submissions to
    [email protected]
    <mailto:[email protected]>

    To subscribe or unsubscribe via the World Wide Web, visit
    http://www.radiance-online.org/mailman/listinfo/radiance-daysim
    <http://www.radiance-online.org/mailman/listinfo/radiance-daysim>
    or, via email, send a message with subject or body 'help' to
    [email protected]
    <mailto:[email protected]>

    You can reach the person managing the list at
    [email protected]
    <mailto:[email protected]>

    When replying, please edit your Subject line so it is more specific
    than "Re: Contents of Radiance-daysim digest..."

    Today's Topics:

       1. Calculation of the solar irradiation with Daysim (Abigail Chi)
       2. Re: Calculation of the solar irradiation with Daysim
          (Christoph Reinhart)

    ----------------------------------------------------------------------

    Message: 1
    Date: Wed, 10 Aug 2016 15:32:22 +0200
    From: Abigail Chi <[email protected] <mailto:[email protected]>>
    To: [email protected]
    <mailto:[email protected]>
    Subject: [Radiance-daysim] Calculation of the solar irradiation with
            Daysim
    Message-ID:
               <CAPSjnYi9cLLYiCAJ+_UzYcNFY3xcShUxVr=VbbbLqRxs2cOfog@mail.gmail.com
    <mailto:[email protected]>>
    Content-Type: text/plain; charset="utf-8"

    Dear all

    I am working on different daylight simulations with Daysim 3.0. My
    interest
    is to calculate the solar irradiation but I have some queries:
    - What solar irradiance spectrum is measured if I use irradiance
    sensors
    instead of illuminance sensors?
    - Could Daysim take into account the SHGC of different window glazing?
    - Is it possible that the glazing system was opaque to the long-wave
    radiation?

    Thanks in advance

    Abigail
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    ------------------------------

    Message: 2
    Date: Wed, 10 Aug 2016 17:36:25 +0000
    From: Christoph Reinhart <tito_@mit.edu <mailto:[email protected]>>
    To: DAYSIM discussion <[email protected]
    <mailto:[email protected]>>
    Subject: Re: [Radiance-daysim] Calculation of the solar irradiation
            with Daysim
    Message-ID:
               <1B23446CBF250648A2FC775DE3FE7E80FF461BC5@OC11expo28.exchange.mit.edu
    <mailto:1B23446CBF250648A2FC775DE3FE7E80FF461BC5@OC11expo28.exchange.mit.edu>>
    Content-Type: text/plain; charset="utf-8"

    - What solar irradiance spectrum is measured if I use irradiance
    sensors instead of illuminance sensors?
    The Daysim program ds_illum has a luminous efficacy model
    according ot Perez built in that converts irradiance into
    illuminances if you choose the latter type of output. Otherwise,
    DAYSIM just uses the direct and diffuse irradiances for an epw
    weather file. Typically those should have been measured with a
    pyranometer, i.e. they should correspond ot the full visible and
    IR spectrum.

    - Could Daysim take into account the SHGC of different window glazing?
    If you use the irradiance output the window transmittance should
    indeed correspond to the window?s SHGC.

    - Is it possible that the glazing system was opaque to the
    long-wave radiation?
    I am unsure what you mean here. DAYSIM/RADIANCE use simplified RGB
    (3 channel) or often effectively 1 channel simulations and do nto
    support a full spectral analysis. I believe that Mehlika Inanici
    is working on a spectral version of RADIANCE.

    Best,

    Christoph

    From: Abigail Chi [mailto:[email protected]
    <mailto:[email protected]>]
    Sent: Wednesday, August 10, 2016 9:32 AM
    To: [email protected]
    <mailto:[email protected]>
    Subject: [Radiance-daysim] Calculation of the solar irradiation
    with Daysim

    Dear all

    I am working on different daylight simulations with Daysim 3.0. My
    interest is to calculate the solar irradiation but I have some
    queries:
    - What solar irradiance spectrum is measured if I use irradiance
    sensors instead of illuminance sensors?
    - Could Daysim take into account the SHGC of different window glazing?
    - Is it possible that the glazing system was opaque to the
    long-wave radiation?

    Thanks in advance

    Abigail

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    ------------------------------

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    End of Radiance-daysim Digest, Vol 26, Issue 1
    **********************************************

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Ecole Polytechnique F�d�rale de Lausanne (EPFL)
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