[Radiance-openstudio] Solar Heat Gain Coefficient (SHGC) Calculations in OpenStudio's Coupled Radiance and EnergyPlus Simulations

[Guglielmetti, Robert]

Depending on what you are using CFS/BSDFs for, you could do most everything you want with the existing OpenStudio stuff, and getting the rest of it working would be a lot easier by leveraging the OpenStudio SDK. At least, you wouldn't be starting from scratch.  I apologize for the dearth of good documentation on this.

As German mentioned, the OpenStudio utility script "MkSchedule.rb" basically illustrates how to create a lighting schedule for OpenStudio (and in turn, for EnergyPlus), and how to replace an existing OpenStudio lighting load schedule, and disable the EnergyPlus daylighting calculations. If the dynamic CFS you have is only two state, and the controls are rotationally invariant, you can do what you need to do now with OpenStudio. If your model has complex spaces that borrow light from other thermal zones, or have orientation-dependent controls operation, then our stuff is a couple of months away from supporting that. But it's possible that your use case would be helpful for us in our debugging, so we should probably talk offline. Interested?

- Rob

From: Justin Shultz <jss5237 at gmail.com<mailto:jss5237 at gmail.com>>
Reply-To: "radiance-openstudio at radiance-online.org<mailto:radiance-openstudio at radiance-online.org>" <radiance-openstudio at radiance-online.org<mailto:radiance-openstudio at radiance-online.org>>
Date: Thursday, March 13, 2014 at 12:08 PM
To: "radiance-openstudio at radiance-online.org<mailto:radiance-openstudio at radiance-online.org>" <radiance-openstudio at radiance-online.org<mailto:radiance-openstudio at radiance-online.org>>
Subject: Re: [Radiance-openstudio] Solar Heat Gain Coefficient (SHGC) Calculations in OpenStudio's Coupled Radiance and EnergyPlus Simulations

Thank you for the responses everyone. This has been extremely helpful.

Paula,

I look forward to reading your thesis, sounds very applicatable. I agree, I think the method that I will need to use will be to tie a Radiance simulation to EnergyPlus. The trick will be figuring out how to transform the Radiance result to EnergyPlus input.

------

Rob,

Thank you for your thorough response. Im excited to see where OpenStudio goes and how it get integrated into the design process. The features you guys are integrating and streamlining will be really fun to test out in the future. Unfortunately, I'm going to need more control over the BSDFs selection and control. This project is also on a short(ish) deadline.

It appears as though to model a custom, dynamic CFS I am going to have to use the radiance 3-phase simulations and manually tie the results into EnergyPlus with a schedule and maybe (EMS for the solar heat gain). The 3-phase method seems to be the best method for this so I'm going to have to read up on that process.

I found "The Three-Phase Method for Simulating Complex Fenestration with Radiance" tutorial by Andrew McNeil. It looks like a good place to start but the disconnnect in my head is how to take the annual simulation results and convert them to a schedule for EnergyPlus. There are a couple programs that do this already, like DAYSIM and OpenStudio, but I haven't figured out how to do it manually. Does anyone have any material on how to manually convert Radiance results to an EnergyPlus schedule?

I've been reading through German Molina's thesis, which has been very helpful so far. I was wondering if there are any tutorials (over tips) that step someone through how to convert Radiance result to an EnergyPlus schedule? I thought there might have been a module in Radiance that did this but I haven't been able to find it.

Thank you for the help everyone, I really appreciate it. Sorry to keep the chain going for so long. I hope this is benefitial to others too!
Justin Shultz
PhD Student


On Thu, Mar 13, 2014 at 12:21 AM, Guglielmetti, Robert <Robert.Guglielmetti at nrel.gov<mailto:Robert.Guglielmetti at nrel.gov>> wrote:
Hi Justin, a couple of answers below, inline (prefixed with “***RPG:”)

- Rob

From: Justin Shultz <jss5237 at gmail.com<mailto:jss5237 at gmail.com><mailto:jss5237 at gmail.com<mailto:jss5237 at gmail.com>>>
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Date: Tuesday, March 11, 2014 at 3:19 PM
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Subject: Re: [Radiance-openstudio] Solar Heat Gain Coefficient (SHGC) Calculations in OpenStudio's Coupled Radiance and EnergyPlus Simulations

Thank you for the response everyone, I appreciate your time and efforts. Sorry to ask such a non-straightforward question.

Hello Denis,

Diva4Rhino is actually a tool I've used for solar analysis in the past. It's a really cool tool, especially since I've seen a lot of grasshopper use in architecture practice lately. Unfortunately, the radiation maps are not what we're looking for because we're trying to apply the result to the interior heat gain of the building. I believe Diva has some functionality for determining the solar heat gain to the interior, because I remember using in the past, but for my current project I don't believe its robust enough.

Thank you, I'll look into ESP-r and see if it's something that can apply.

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

Hello Rob,

No problem at all, I landed on the page from a google search and didn't notice the subscribe button from the radiance page. Andrew was very helpful.

***RPG: Yes, Andrew generally is. =8-)

The EnergyPlus lighting load schedule, generated from the Radiance daylight simulation, makes sense to me. It's really awesome that you made those calculations so streamline. I do whole building simulation in an architecture graduate program and I can already see how it would be applied in many design applications. Though, I'm a bit confused how the solar heat gain is effected from the OpenStudio model, with Radiance turned on.

How does the coupled Radiance and EnergyPlus method impact the solar heat gain calculations in EnergyPlus (if at all)? In other words, if two identical buildings were modeled, one with a CFS and Radiance and one without, would the CFS OpenStudio model have a reduced solar heat gain? Is the BSDF applied somewhere in the EnergyPlus model to determine new solar heat gain values or through Radiance? If so, maybe you can elaborate on how it's applied. Is the reduced solar heat gain due to the modules in EnergyPlus or a data flow between Radiance and EnergyPlus?

***RPG: Great question(s). We are implementing using BSDFs on the Radiance side to model shades, blinds, and diffusing glass, in a general way. All of these things can also be modeled in EnergyPlus. The plan is to upload a library of generic BSDFs describing:

1. Clear glazing (1-91% VLT)
2. Clear glazing with venetian blinds (slats preset to something aggressive, and blinds fully extended, i.e. covering the entire window)
3. Clear glazing with shadecloth material (5% openness, fully extended)
4. Diffuse glazing (1-70% VLT)

These BSDFs all correspond to various EnergyPlus Construction Assembly.Fenestration.Window elements or material properties. We also have exposed several of the EnergyPlus shade control options:

1. Always on (down)
2. Always off (up)
3. Operate by schedule (user-supplied)
4. On if high solar

The user applies shading controls to one or more windows in the OpenStudio model; at run time the OpenStudio-to-Radiance translator will map the appropriate BSDF pairs to each window group (windows sharing orientation and shading control) so that the daylight availability will be calculated by Radiance, and will be based on user-specified operable shades and control. After that, OpenStudio works like it always has during a Radiance simulation: the electric lighting schedules are computed, and passed back to the OpenStudio model, which then computes the building energy use with EnergyPlus.

In other words, it’s still a serial process, where Radiance goes first and does a daylight simulation, thus informing the electric lighting operation, which is passed to EnergyPlus for the rest of it. It’s integrated, but could hardly be called “cosimulation”. Not yet, anyway.

Hopefully this all makes sense. (?) We hope to release all of this functionality in the next couple of months.

- Rob


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