Reducing Viper Run-time

[Arpan Bakshi]

Q for the Grasshoppers in the group

As always, hats off to the geniuses at GSD/MIT who created DIVA and Viper. I work mostly on the simulation side with DOE2 and IES, and I attest to how much of a challenge those tools are on their own without trying to connect them to Rhino!

I am trying to running iterative shade depths connected the EnergyPlus components. I have all of this set up along with Hoopsnake which is an iterator, taking outputs and changing inputs.

The problem I am running into is the length of time the EnergyPlus solar calculations are taking! Are there any known shortcuts in the settings to simply the simulations and reduce run-time? I am really only looking to find the peak load hour and see how it increases/reduces with the shade design.

[Jon Sargent]

Arpan,

Are you running an annual simulation each time?  If your interest is peak loads, you can select an extreme summer day from the Viper settings pop-up form (under Run Period in the Simulation Parameters tab).

-Jon

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[Kevin Pratt]

As an aside, the length of your simulation is probably due to the complexity of your shading devices.  This is an energy plus issue and you can try the different radiant forcing function calcs in E+ (like excluding diffuse bounces, etc.) but you best bet is to have a lot less shading geometry. The shading calc time in E+ roughly increases proportional to the square of the number of surfaces. 

Kevin Pratt
Assistant Professor
Department of Architecture Art and Planning
Cornell University
Ithaca, NY 14853

Principal, Epiphyte Lab
www.epiphyte-lab.com

On Sun, Mar 25, 2012 at 4:45 PM, Arpan Bakshi <arpan...@gmail.com> wrote:

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[Arpan Bakshi]

Thank you Jon and Kevin. Reduced run-time to 13 minutes by,

• Typical Day instead of Annual
• 1 time step per hour instead of 2
• Change in solar distribution from FullInteriorandExterior to FullExterior
• Change in shadow calc overlap from 15000 to 5000

I understand the accuracy risks but am unable to use the iterative process without them!

One possible workflow would be to run through a series of low accuracy sims for comparative studies and then follow up with a detailed study on a select few design option(s)

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Arpan