Re: [EnergyPlus_Support] relation between a time simulation and the building surface

[Jason Kirkpatrick <jason.alan.kirkpatrick@xxxxxxxxx>]

Camille,

It has been my experience that there is not necessarily a linear relationship between number of surfaces (or number of zones) and run time. Often this run time is more dependent on the number of air loops you are simulating, and also the complexity of the systems. Systems employing radiant cooling or heating strategies often take much longer. Also, improperly set up files can take extraordinarily long because the temperatures are having convergence problems.

There is some documentation regarding run time optimization in the "Tips_andTricks_Using_EnergyPlus.pdf" document included with the installation.

One way to reduce run time is to include the following:

Output:Diagnostics, CreateMinimalSurfaceVariables; 

Also, it is generally a good idea to do smaller sample runs of a week in summer and a week in winter to perform troubleshooting measures / make sure things are operating properly.

This can be accomplished through modifying the SimulationControl and RunPeriod objects.

SimulationControl,
    Yes,                     !- Do Zone Sizing Calculation
    Yes,                     !- Do System Sizing Calculation
    Yes,                     !- Do Plant Sizing Calculation
    No,                      !- Run Simulation for Sizing Periods
    Yes;                     !- Run Simulation for Weather File Run Periods

RunPeriod,
    Summer Week,   !- Name
    7,                       !- Begin Month
    15,                       !- Begin Day of Month
    7,                      !- End Month
    22,                      !- End Day of Month
    UseWeatherFile,          !- Day of Week for Start Day
    No,                      !- Use Weather File Holidays and Special Days
    No,                      !- Use Weather File Daylight Saving Period
    Yes,                     !- Apply Weekend Holiday Rule
    Yes,                     !- Use Weather File Rain Indicators
    Yes,                     !- Use Weather File Snow Indicators
    1;                       !- Number of Times Runperiod to be Repeated

RunPeriod,

    Winter Week,   !- Name
    1,                       !- Begin Month
    15,                       !- Begin Day of Month
    1,                      !- End Month
    22,                      !- End Day of Month
    UseWeatherFile,          !- Day of Week for Start Day
    No,                      !- Use Weather File Holidays and Special Days
    No,                      !- Use Weather File Daylight Saving Period
    Yes,                     !- Apply Weekend Holiday Rule
    Yes,                     !- Use Weather File Rain Indicators
    Yes,                     !- Use Weather File Snow Indicators
    1;                       !- Number of Times Runperiod to be Repeated

Also, I have found that version 6 (the newest release of EnergyPlus) has greatly improved run time over previous versions, so if you are using a previous version, I would suggest updating to the newest release.

Hope this helps.

Jason

On Wed, Jan 12, 2011 at 5:02 AM, le_carambar <le_carambar@xxxxxxxx> wrote:

 

Dear E+ user,

Do you know if there is an approximative relation between the simulation time and the building surface or the number of zone.

For instance, a 2000m² building will be 2 times longer to be simulated than a 1000m² or 4 times longer ?

Thanks,

Camille

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