Long-Term Simulation

In addition to the Short-Term Simulation, users can run Long-term simulations which can be anywhere from one day to one year long. When you click on the Long-term Simulation tab, you are presented with the view in Figure 3-1. As you can see, the layout for the Long-term Simulation is much like the Shot-term Simulation. In the Simulation Controls, you can set the variables that will be used for the simulation. To the right, you can view any physical changes you make to the building.
Figure 3-1 Long-Term Simulation Windows
Long-Term Simulation

Run Options

In the Run options tab, the first input you see is where to store the result from the simulation, Run 1 or Run 2. Like with the Short-Term simulation, this is for analysis later and so you can compare two different runs. For now, just leave it as Run 1.

You can also set the length of the simulation, but for now just leave it at 1 year.

The variables listed below that are actually brought over from the Short-Term Simulation and you cannot set them here. To set them, you have to go back to the Short-Term Simulation and click on Inputs. There you will see some variables with blue, "LT" flags LT Flag

Figure 3-2 Short-Term Simulation Import
Short-Term Simulation Import

Those variables with the blue "LT" flag will be imported into the Long-Term Simulation once they are updated in the Short-Term Simulation. In fact, this is the only way to set there variables as you cannot update them in the Long-Term Simulation. Those with grey "LT" flags move in the other direction; variables set in the Long-Term Simulation will be updated in the Short-term Simulation, however these can overwritten by the user.

Those variables with the blue "LT" flag will be imported into the Long-Term Simulation once they are updated in the Short-Term Simulation. In fact, this is the only way to set there variables as you cannot update them in the Long-Term Simulation. Those with grey "LT" flags move in the other direction; variables set in the Long-Term Simulation will be updated in the Short-term Simulation, however these can overwritten by the user.

The table below tells you where you can find each important variable for the Long-Term Simulation:

Long-Term Variable Short Term Inputs Menu
Room Temp Heating Set Point System
Room Temp Cooling Set Point System
Supply Air Temp Set Point System
Heating Coil Design Heating Capacity Heating Coil
Cooling Coil Design Cooling Capacity Cooling Coil
VAV min Volume Flow Rate Ratio VAV box
Reheat Coil Design Heating Capacity VAV box

The value of these variables does not matter for this tutorial, so just leave them at their default value.

Environment

Figure 3-3 Long-Term Simulation Environment
Environment Tab

In the Environment tab, you can choose where the building is located and therefor what type of weather it is exposed to. Right now, there are a limited number of cities. These cities are divided up into three regions:

Pacific:
  • San Francisco, CA
  • Los Angeles, CA
  • Phoenix, AZ
  • Salem, OR
  • Boise, ID
Northeast:
  • Baltimore, MD
  • Burlington, VT
  • Chicago, IL
  • Duluth, MN
  • Fairbanks, AK
South:
  • Miami, FL
  • Houston, TX
  • Memphis, TN
  • El Paso, TX
  • Albuquerque, NM

NOTE: At the time of this writing, there is a bug in the display of the cities. If you change the Region, the Cities list will not update until you click on a city (any city) and then the list will update and you can choose the city of your choice.

You can just leave it as San Francisco for now.

Properties

Figure 3-4 Long-Term Simulation Properties
Properties Tab

In the properties tab, you can alter the physical characteristics of the building. Although the general size and dimensions of the structure are fixed in this release, you can alter the window-to-wall ratio and the type of windows.

Under type, you can choose either Punched windows, or Strip windows. As you change this selection, notice that the image to the left changes. Choose Punched Windows

Figure 3-5 Window-to-Wall Ratio
WWR

The Window-to-Wall Ratio describes what percentage of the façade the glazing represents. The default 0.4 means that 40% of the building façade are windows. This value can be adjusted by moving the sliders for each orientation. As you move the sliders, you can see the image update. To change which orientation if being shown in the image, use the drop down menu in the upper left of the building image.

Let's make the North WWR 0.8 and the West 0.8. Leave the other two at their default.

Loads

Figure 3-6 Long-Term Simulation Loads
Loads

The final tab is the Loads tab. Here you can define the internal gains in the building. Here you can define the Equipment load, the Lighting Power Density, and the Occupant density. Just leaves these as their default values for now.

Now hit Start Simulation. It will take a few minutes for the simulation to compute. Once it does, move on to Analysis.



Click here to go to continue on to the Analysis Tool Tutorial