[Radiance-general] Using Radiance to Generate Lighting and Solar Surface Heat Gain Schedules for EnergyPlus

[Andrew McNeil]

Actually, when you use the scheduled surface heat gains, energy plus
redistributes energy to account for inter-reflection. It's not as accurate
as computing inter-reflection in Radiance.

But generally, I agree with German that the standard EnergyPlus CFS method
is simpler to implement. We wouldn't have developed our Radiance method if
EnergyPlus supported CFS at the time.

Andy



On Tue, Apr 8, 2014 at 3:12 PM, CHI-German Molina <gmolina at hdlao.com> wrote:

> Justin,
>
> I understand there is something called "Scheduled Surface Gains" that you
> can use for "importing" solar gains in surfaces. However, I am not sure if
> this is advisable because of the difficulties in calculating the solar
> gains on each surface. Also, if I remember correctly, Andy's method did not
> calculate solar inter-reflection on interior surfaces, so I believe that
> the "standard" EnergyPlus CFS calculation should do...? it will
> re-distribute the beam radiation just as Radiance would... the diffuse,
> though, I believe is averaged.
>
> Using Andy's method, I believe, would be justified in cases with complex
> interior and exterior geometries, where Radiance's ray-tracing works better.
>
> That is my opinion... not sure what others may think.
>
> Bye
>
>
> 2014-04-08 18:50 GMT-03:00 Andrew McNeil <amcneil at lbl.gov>:
>
> Justin,
>>
>>  genBSDF "change wavelength tag from visible to NIR":
>>
>> Since that presentation the tag used by Window has been changed from NIR
>> to solar, so you should use solar.
>>
>> Creating Surface Heat Gain Schedule:
>>
>> We created a pseudo view matrix by tracing rays from the window into the
>> space and binning rays based on the intersection location and material
>> modifier. You can use genklemsamp, but have to flip the sign on the z
>> component of the vector.
>>
>> Using Schedules in EnergyPlus:
>>> "EnergyPls code modified to allow schedule of surface heat gains"
>>> (modification by Thierry Nouidui and Brian Coffey). I was wondering if this
>>> has be implemented, if so how? I saw in the EnergyPlus EMS manual that the
>>> EMS system can be used to control exterior building variable, is this the
>>> same system?
>>
>> The ability to schedule internal surface heat gains has been incorporated
>> into the trunk of EnergyPlus starting with version 8.1. The relevant
>> objects are:
>>
>> SurfaceProperty:SolarIncidentInside
>> ComplexFenestrationProperty:SolarAbsorbedLayers
>>
>> The built in BSDF module gives identical results as using Radiance to
>> determine solar absorption in the CFS layers.  However using Radiance
>> offers some improvement in the interior distribution of energy (though it
>> might not be worth using Radiance for this now that EnergyPlus has built in
>> BSDF capabilities).
>>
>> That is the extent of my knowledge of EnergyPlus. I don't want to be
>> mistaken for someone who knows things about EnergyPlus.
>>
>> Andy
>>
>>
>>
>> On Tue, Apr 8, 2014 at 1:47 PM, Lars O. Grobe <grobe at gmx.net> wrote:
>>
>>> Hi Justin!
>>>
>>> > genBSDF "change wavelength tag from visible to NIR":
>>> > How would one go about running genBSDF for NIR? I read somewhere that
>>> the material properties should be changed for NIR, but we're not sure how
>>> to do that. Is there a hidden function that can be added to genBSDF to run
>>> for NIR?
>>>
>>> genBSDF as Radiance offer three channels. Usually we fill those with
>>> data for three bands in the visible light range and call them RGB. However
>>> you can assign them NIR if you need to. In this case, make R=G=B=NIR,
>>> meaning that you need to first define you NIR band and than use reflection
>>> / transmission measured for this band when setting up you model. Run
>>> genBSDF and the resulting output will be the BSDF in the NIR-band as you
>>> defined it. The tag mentioned is in the XML-file, open it with a text
>>> editor to change it.
>>>
>>> Did anyone get a similar approach working with ESP-r?
>>>
>>> Cheers, Lars.
>>> _______________________________________________
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>>> Radiance-general at radiance-online.org
>>> http://www.radiance-online.org/mailman/listinfo/radiance-general
>>>
>>
>>
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>>
>
>
> --
> *Germán Molina L.*
> Ingeniero Trainee
> Hunter Douglas Chile S.A.
> Celular +569 89224445
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