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OpenStudio Tutorial
Introduction EnergyPlus Background EnergyPlus models heating, cooling, lighting, ventilating, and other energy flows as well as water in buildings. EnergyPlus is a new‐generation building energy simulation program based on DOE‐2 and BLAST, with numerous added capabilities. Some of these innovative simulation capabilities include time steps of less than an hour, modular and plant integrated systems with heat balance‐based zone simulation, multi‐zone air flow, thermal comfort, water use, natural ventilation, and photovoltaic systems. Released in April 2001, the program was developed jointly by Lawrence Berkeley National Laboratory, the University of Illinois, the U.S. Army Construction Engineering Research Laboratory, GARD Analytics, Inc., Oklahoma State University and others, with support from the U.S. Department of Energy, Office of Building Technology, State and Community Programs. EnergyPlus is a trademark of the U.S. Department of Energy.
Zoning Differences SketchUp Zones: Warehouse
In SketchUp, the interior walls make up the zones. For example, notice the warehouse picture above. Since there are no interior walls in the warehouse it is modeled as one zone large rectangular zone. EnergyPlus Zones: Warehouse
EnergyPlus zones are different then SketchUp zones. In the case of the warehouse, even though there are no interior walls, the energy model should be separated into perimeter and core zones. This is important to investigate daylighting, to separate the effects of infiltration from the perimeter and core, and to correctly account for solar gains into the building. Also, unlike SketchUp zones which can be any shape imaginable, EnergyPlus thermal zones must be concave, meaning that every surface in the zone should be in the line of sight will all other surfaces of the zone.
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Creating a Simple Energy Model Download and Launch the Software Download and install Google SketchUp 7 from http://sketchup.google.com/. Download and install OpenStudio from http://apps1.eere.energy.gov/buildings/energyplus/openstudio.cfm. Start Google Sketchup. You will be prompted to choose a template.
Choose the ‘Engineering – Feet’ template and click ‘Start using SketchUp’. Delete the drawing of the person standing at the axis origin by clicking on it and pressing ‘Delete’ Create an EnergyPlus Zone Create a new EnergyPlus zone by choosing Plugins ‐> OpenStudio ‐> New Zone Tool from the main menu. A small, blue cross‐hair should appear at the tip of the cursor arrow. Place the cursor at the axis origin (a small yellow dot will appear at the axis origin) and click. This will place a blue box on the screen. This is our EnergyPlus zone. If the blue box it not visible, try correcting the zoom. Change the view to fit the object by going to Camera ‐> Zoom Extents from the main SketchUp menu. Now you can zoom in and out with the mouse wheel to fit the object in the window to your liking.
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Note that if you click on the screen outside of the blue box that it will disappear from view. This is normal. To better select the box turn on hidden geometry by going to View ‐> Hidden Geometry from the main menu. A check mark should appear next to hidden geometry on the View menu. Now a small gray cross‐hair will be visible at the opposite corner of the box.
This cross hair will allow the user to better select the EnergyPlus zone. Note that if you click on the gray cross‐hair the EnergyPlus zone is outlined in blue again. EnergyPlus Zone Details Double click on the small, gray cross‐hair now visible with hidden geometry turned on. The blue outline of the EnergyPlus zone should become a broken, black line. We have ‘activated’ our EnergyPlus zone. Note that in order to modify the EnergyPlus geometry the EnergyPlus zone MUST be ‘activated’ (outlined with the broken black line).
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This is what separates the EnergyPlus geometry from SketchUp geometry. Any object drawn in a ‘un‐activated’ EnergyPlus zone is only SketchUp geometry and will not be written out to the EnergyPlus IDF file. It is VERY important to make sure the zone is activated before you start creating geometry. Modifying Geometry within the EnergyPlus Zone First create a square floor for the model. Make sure that your EnergyPlus zone is still ‘active’ (outlined with the broken black line). Choose the rectangle tool by going to Draw ‐> Rectangle from the main menu. Start the square at the axis origin by clicking on the origin. Next designate in the size of the square by typing ’20, 20’ and pressing enter (you can see the numbers being input in the lower right hand corner of the screen). This will create a 20’ by 20’ square floor. Note the gray color of the floor. This color is automatically generated by OpenStudio that designates this surface as a floor in EnergyPlus.
Next ‘pull’ the rectangle up to create a three‐dimensional cube. Make sure that your EnergyPlus zone is still ‘active’ (outlined with the broken black line). Choose Tools ‐> Push/Pull from the main menu. Hover over the rectangle that you just created with the push/pull tool. The surface should be covered with
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small blue dots when the tool is above the rectangle. This means that the tool will select that rectangle. Hover over the rectangle until the blue dots appear and click once with the mouse. The tool will ‘grab’ the rectangle surface. Move the mouse up and down to see how the tool works. Move the mouse slightly up (so that the rectangle is projecting towards the top of the screen), type ‘10’, and press enter. This will ‘pull’ the rectangle up to create a 10’ tall cube. Notice that OpenStudio automatically colored the walls and the roof of the cube. These surfaces are now designated in EnergyPlus.
Saving the IDF File It is crucial to save the IDF file early and often. The IDF file is separate from the SketchUp file and saving the SketchUp file will not preserve the IDF information. To save the IDF file, chose Plugins ‐> OpenStudio ‐> Save from the main menu. If it is the first time you are saving the file a dialog box will prompt you for a location and name. Call the file ‘tutorial1.idf’. Again, it is very important to save the IDF file early and often. Creating Fenestration Objects OpenStudio can also be used to generate fenestration objects. To begin, first make sure that your EnergyPlus zone is still ‘active’ (outlined with the broken black line). To draw a window, use the rectangle tool to create a rectangle on a wall that is completely contained within the wall surface. OpenStudio will recognize that this as a window and automatically color the rectangle a transparent blue and reference the surface as a window in EnergyPlus. Create one window on the front face of the cube and one on the side face, as in the picture below.
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Next create a door on the front face of the cube. To begin, first make sure that your EnergyPlus zone is still ‘active’ (outlined with the broken black line). A door will again be drawn with the rectangle tool, but this time the bottom edge of the rectangle must lie along the bottom edge of a wall. OpenStudio will recognize that this as a door and automatically color the rectangle a dark brown and reference the surface as a door in EnergyPlus.
A skylight is created the same way as a window, but the rectangle is drawn on a roof instead of a wall. To begin, first make sure that your EnergyPlus zone is still ‘active’ (outlined with the broken black line). Create one skylight on the roof as in the picture below.
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Create Shading Objects OpenStudio can be used to create shading objects. First create an overhang on long window. To begin, select the appropriate tool by going to Plugins ‐> OpenStudio ‐> New Shading Group Tool. This tool is very similar to the new zone tool. Place the new shading group at the top corner of the window buy clicking the mouse there, just like you placed the new zone at the axis origin. Similar to the new zone tool, in order to edit the shading group geometry you must make the group ‘active’. To do this, double click on the small gray cross‐hair that was created when you placed the new shading group. When the shading group is ‘active’ you should see the rest of the model become lighter. Use the rectangle tool to create a shading overhang above the window as shown in the picture below.
OpenStudio can also be used to create detached shading objects, such as other buildings. Create a detached shading object behind our building representing another 40 foot tall building. This time it will be a little more difficult to place the shading zone, so let’s use the SketchUp guides to help us. To start with the guides select the tape measure tool from Tools ‐> Tape Measure from the main menu. Using
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the tape measure tool, click once on the red axis and move the mouse towards the back of the building. You should see a broken gray line running parallel to the red axis that moves with the mouse. To make sure you are creating a line parallel to the red axis you should see a green line with arrow heads on both ends perpendicular to the red axis and the broken gray guide line you are creating, as shown below.
To place the guideline exactly, type ‘40’ while after you first clicked on the red axis with the tape measure and started moving the mouse towards the back of the building. Make sure that the green line appears as in the picture above before you type in the dimension. You have just created a guide line 40’ from the front of the building parallel to the red axis. Now we need to create another guide line on the green axis so that our mouse will ‘snap’ to the intersection of the two guide lines. To create another guide line on the green axis, select the tape measure tool from Tools ‐> Tape Measure and double‐click on the green axis. The new guideline might be difficult to view because it is directly on top of the green axis. The intersection of these guide lines is where you will place your shading zone. To begin, select the appropriate tool by going to Plugins ‐> OpenStudio ‐> New Shading Group Tool. Place the new shading group at the intersection of the guidelines. If the guidelines were placed correctly, the new shading group tool should ‘snap’ to the intersection of the two guide lines that you created. Again, in order to edit the shading group geometry you must make the group ‘active’. To do this, double click on the small gray cross‐hair that was created when you placed the new shading group. When the shading group is ‘active’ you should see the rest of the model become lighter. Use the rectangle tool to create a 20’ wide by 20’ tall shading surface as shown in the picture below. Because the shading surface is in a different plane than the rest of the building, you may find it difficult to draw. You could use guide lines to create the border of the rectangle and then your rectangle tool will snap to the intersections of the guide lines. You could also switch the view in SketchUp by going to Camera ‐> Standard Views ‐> Back from the main SketchUp menu. If you are in this view your rectangular shading surface should draw in the correct (blue and red axis) plane. To return to the previous view, chose Camera ‐> Standard Views ‐> Front and then Camera ‐> Standard Views ‐> Iso from the main SketchUp window.
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The guide lines can be removed by going to Edit ‐> Delete Guides. This will also remove the hidden geometry, so make sure that you have all of you zones/shading objects placed correctly and have some geometry in the zones/shading group or it will be difficult to ‘activate’ those zones once the hidden geometry is gone. Using the Outliner Window Next we will use the outliner window to review the zones that we have placed. To access the outliner window from the main menu chose Window ‐> Outliner. The window that opens should look similar to below.
You can use the outliner window to select the EnergyPlus objects by clicking on them. Double clicking on an object in the outliner window will ‘activate’ the object. You should have two EnergyPlus shading groups and one EnergyPlus zone with a random six‐digit alphanumeric name. If you have any additional objects placed on accident select them in the outliner window and delete them. Using the Object Info Tool OpenStudio also has the ability to modify the EnergyPlus object information. To access the object info tool, chose Plugins ‐> OpenStudio ‐> Object Info. This will open the object info window.
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The class type will change as objects are selected on the screen. If nothing is selected, the class type is ‘Building’. Change the name of the building to ‘Tutorial’ and the solar distribution to ‘Full Interior and Exterior with Reflections’. Click on the zone in the main SketchUp drawing area and you will see the class type change to ‘Zone’ in the object info window. Change the Zone name from the default six digit alphanumeric zone name to ‘Main Zone’. Open the outliner window again; notice that the EnergyPlus zone name has changed.
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With the object info window still open double click on ‘Main Zone’ in the SketchUp window to ‘activate’ the zone. Notice how the object info window changes as you select a wall, door, roof, or window. For building surfaces (walls, roofs, etc.) the surface name, type, construction, zone, outside boundary conditions, and the ground view factor. Using the object info window you can change the name of the surface, the surface type, the construction, and the base surface for fenestration surfaces. To test this out, change the door name to ‘Door’, the window without an overhang to ‘Window’, the window with an overhang to ‘Window – Overhang’, and the skylight to ‘Skylight’. Toggle between surfaces by clicking on them on the main SketchUp window. Running EnergyPlus in SketchUp The OpenStudio plugin can be used to perform EnergyPlus simulations. To start, first download and install Energy Plus from http://apps1.eere.energy.gov/buildings/energyplus/cfm/reg_form.cfm. Next set the preferences in OpenStudio by going to Plugins ‐> OpenStudio ‐> Preferences. This will open the preferences dialog box.
Set the EnergyPlus engine path to the location where you have installed EnergyPlus on your computer and hit ‘OK’. You may get the following error message.
This error can be ignored, for it is only a difference in the build number of EnergyPlus 3.1. Click ‘OK’ to proceed. Next open the run simulation window by going to Plugins ‐> OpenStudio ‐> Run Simulation. The run simulation dialog box will open.
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Check the checkboxes in the run simulation dialog box as shown above. To set the EPW path, browse to your EnergyPlus installation directory and open the weather data folder. Open this folder and select the EPW file for Chicago. Make sure that you uncheck ‘Annual Simulation’ and change the start and end dates to those shown above or it will take a long time to process the results visually using OpenStudio. Once your run simulation dialog matches above click the ‘Apply’ button and then the ‘Run’ button. You may get the following error message.
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This error can be ignored, for it is only a difference in the build number of EnergyPlus 3.1. Click ‘OK’ to proceed. A shell command window will launch and you will see that EnergyPlus is running. The simulation should be very quick. The error file will then open in a text editor and the HTML file will open in the default internet browser. The simulation is now complete. You can inspect and close the error file (should be some warnings but no severe errors) and the HTML file. Viewing Results OpenStudio can be used to visually view EnergyPlus results. To begin, go to the main SketchUp menu and chose Plugins ‐> OpenStudio ‐> Renderings ‐> Settings. This will open the rendering settings dialog box.
Set the data path by browsing to the directory where you saved your IDF file. There should now be a, ESO file, an HTML file, an ERR file, and a CSV file generated by EnergyPlus during the simulation. The ESO
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file is the one we want to choose for the data path. The run period will automatically be filled once the ESO file is chosen for the data path. Set the rest of the Rendering settings as shown above and click ‘OK’. The dialog box will close and nothing will appear to change. We now need to set OpenStudio to render by data value instead of by surface class. To do this go to the main SketchUp menu and chose Plugins ‐> OpenStudio ‐> Renderings ‐> By Data Value. Most likely, the model will now all turn white. The model is supposed to color based on surface temperature, but it is appearing white because we have not set the time to match up with our simulation run time for the first week of January. To set the model time to match the simulation time from the SketchUp main menu choose Plugins ‐> OpenStudio ‐> Animation ‐> Settings. This will open the Animation Settings dialog box.
Check the ‘Match simulation run period’ and the ‘Repeat when finished’ checkboxes as shown above and hit ‘OK’. Lastly we need to reset the time to the beginning of the run period. To do this go to the SketchUp main menu and chose Plugins ‐> OpenStudio ‐> Animation ‐> Reverse to Marker. Make sure that the bottom left corner of the screen indicated January 01. If it says January 08, chose Plugins ‐> OpenStudio ‐> Animation ‐> Reverse to Marker again. Now the bottom left corner of the screen should say January 01. Also, turn on shadows to see the position of the sun by going to View ‐> Shadows from the main SketchUp Window. Now that we have reset the time and have shadows on, we are finally ready to view the animation. To begin the animations go to the SketchUp main menu and chose Plugins ‐> OpenStudio ‐> Animation ‐> Play. At the bottom left of the screen you will see the time and date as the animation progresses. Notice that the walls, windows, and doors are all slightly different colors, meaning that their temperature is different because of their material. While the simulation is running we can view the temperature scale by going to the main SketchUp menu and chose Plugins ‐> OpenStudio ‐> Renderings ‐> Color Scale. Stop the animation the same way you stated it, by going to the SketchUp main menu and chose Plugins ‐> OpenStudio ‐> Animation ‐> Play. Once the date passes the end of our run period the model will turn white because there is no data for it to display. The animation can begin from the beginning by first halting playback by going to the SketchUp main menu and chose Plugins ‐> OpenStudio ‐> Animation ‐> Play and then resetting the time by going to the SketchUp main menu and chose Plugins ‐> OpenStudio ‐> Animation ‐> Reverse to Marker.
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Create HVAC Using EnergyPlus Example File Generator (EEFG) Open an internet browser and navigate to the EnergyPlus Example File Generator at the following address: http://apps1.eere.energy.gov/buildings/energyplus/cfm/inputs/. Enter your e‐mail address, chose the simple model, target standard ASHRAE 90.1‐2004 and change the units to English (I‐P). Check the checkbox that says ‘Upload IDF file’. Change the location to Chicago, change the building type to office/professional, and enter a short building description. Keep the rest of the radio buttons on smart default and click the ‘Submit’ button near the bottom of the page. On the next page you can browse for the IDF file that you just created, and then click the ‘Submit’ button at the bottom of the page. The last page should say EnergyPlus Example File Generator: Complete. You should receive an e‐mail shortly containing your input, output, and results. The EEFG can be used to insert proper EnergyPlus HVAC systems into IDF files that you have created in SketchUp. Try opening the IDF file that you received from the EEFG e‐mail in SketchUp and running an annual simulation. Inspect the HTML file for HVAC system information. We have now successfully created a simple working EnergyPlus model in OpenStudio and used the EEFG to create an HVAC for the model.
Adding a Second Zone to the Simple Model If you have the IDF file from the EEFG open, re‐open the IDF file ‘tutorial1.idf’ that you created earlier. Next, rename the IDF file by going to the main SketchUp menu and choosing Plugins ‐> OpenStudio ‐> Save As. Rename the file ‘tutorial2.idf’. We will now add a second zone to the model. First use the orbit tool (Camera ‐> Orbit) to rotate the model around to the back side. Create a new EnergyPlus zone by choosing Plugins ‐> OpenStudio ‐> New Zone Tool from the main menu. Place the new zone at the back corner of the building as shown in the picture below:
Create a 10’ by 10’ square and pull it up to the height of the other zone (10’) as shown in the picture below.
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Remove the hidden geometry by choosing Edit ‐> Delete Guides from the main SketchUp menu. We have successfully created a second zone. Name the zone ‘New Zone’ using the object info tool, found under Plugins ‐> OpenStudio ‐> Object Info. The outliner window should appear as follows.
Add a window and a door to the new zone, as shown in the picture below.
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Finally we need to match up the mating surfaces of these two zones. To begin, we must first split the surface of the ‘Main Zone’ because it is twice as large as the opposing surface of the ‘New Zone’. To begin, let’s first hide the ‘New Zone’ so we can clearly see the ‘Main Zone’. First turn off hidden geometry (or the ‘New Zone’ will still be visible when we hide it) by going to View ‐> Hidden Geometry from the main menu. Next, highlight the ‘New Zone’ so that it is outlined in blue (but do not double‐click to ‘activate’ the zone) and go to Edit ‐> Hide from the main menu. The ‘New Zone’ should disappear from the screen. Next, create a guide line to divide the back wall of the ‘Main Zone’ into two parts. The ‘New Zone’ ends 10’ from the ‘Main Zone’ so create the guideline there, as shown in the picture below.
Next, ‘activate’ the ‘Main Zone’ by double‐clicking and draw a line from the top edge to the bottom edge of the back wall on top of the guide line. To draw a line on the surface chose Draw ‐> Line from the main SketchUp menu. Remove the guide line by choosing Edit ‐> Delete Guides from the main SketchUp menu. The ‘Main Zone’ should look like the picture below and you should be able to select two individual surfaces (covered in a grid of blue dots) on the back wall of the ‘Main Zone’.
Next, name the surface that is highlighted in the picture above ‘Main Zone Interior Wall’ using the object info tool. To access the object info tool, chose Plugins ‐> OpenStudio ‐> Object Info. Once we name the mating wall from the ‘New Zone’ we will then set the boundary conditions and constructions so that these zones reference each other in EnergyPlus. In order to accomplish this, first unhide the ‘New Zone’
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by ‘de‐activating’ the ‘Main Zone’ (click the mouse outside of the zone) and choosing Edit ‐> Unhide ‐> All from the main Sketchup menu. Now hide the ‘Main Zone’ the same way you hid the ‘New Zone’. Rotate the view so that you now see the surface of the ‘New Zone’ that mates with the ‘Main Zone’. You might want to hide the window shading surface as well if it obstructs your view. Next, ‘activate’ and highlight the mating wall of the ‘New Zone’ (see picture below).
Name the surface ‘New Zone Interior Wall’ using the object info tool. To access the object info tool, chose Plugins ‐> OpenStudio ‐> Object Info. Also use the object info tool to set the construction type to ‘Interior Wall’, the outside boundary condition to ‘Surface’ and the outside boundary condition object to ‘Main Zone Interior Wall’. When you are done, the object info window should look like the following.
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Now unhide the ‘Main Zone’ by ‘de‐activating’ the ‘New Zone’ (click the mouse outside of the zone) and choosing Edit ‐> Unhide ‐> All from the main Sketchup menu. Now re‐hide the ‘New Zone’ and rotate the view so that you now see the surface of the ‘Main Zone’ that mates with the ‘New Zone’. Next, ‘activate’ and highlight the mating wall of the ‘Main Zone’ and change the object info to match the picture below.
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We have now successfully matched the surfaces of these two zones. These steps need to be followed for all zones that have mating surfaces to ensure that the EnergyPlus file is set up correctly. Run the EnergyPlus simulation using the same settings as before.
Investigating the Effects of Glazing on Energy Performance Open Z6 House IDF Launch Google SketchUp. Open the z6 house IDF file (provided) by going to the main SketchUp menu and choosing Plugins ‐> OpenStudio ‐> Open. Browse to the location of the z6 house IDF file and click on ‘Open’.
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EnergyPlus Simulation First double‐check your preferences in OpenStudio by going to Plugins ‐> OpenStudio ‐> Preferences. This will open the preferences dialog box.
Set the EnergyPlus engine path to the location where you have installed EnergyPlus on your computer and hit ‘OK’. Next open the run simulation window by going to Plugins ‐> OpenStudio ‐> Run Simulation. The run simulation dialog box will open.
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Check the checkboxes in the run simulation dialog box as shown above. To set the EPW path, browse to the location of the provided Los Angeles EPW file. Once your run simulation dialog matches above click the ‘Apply’ button and then click the ‘Run’ button. This simulation will take a couple of minutes to complete Remove Un‐Shaded Windows Rename the IDF file by going to the main SketchUp menu and choosing Plugins ‐> OpenStudio ‐> Save As. Rename the file ‘z6house_shadedwindows.idf’. Remove the un‐shaded windows from all the zones. To remove the windows, first ‘activate’ the zone by double‐clicking on it. Then double‐click on the window surface so that that blue dots appear on the window surface and the window border is
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highlighted in blue. Then hit the ‘delete’ key. Repeat this for all of the windows that are not shaded in all of the zones.
Run the EnergyPlus simulation again with the same settings as before. Remove All Windows Rename the IDF file by going to the main SketchUp menu and choosing Plugins ‐> OpenStudio ‐> Save As. Rename the file ‘z6house_nowindows.idf’. Remove all windows from all the zones.
Run the EnergyPlus simulation again with the same settings as before. Next, compare the results of all simulations by opening up the HTML files and noting how glazing effects energy performance. Focus attention on the end use table, looking particularly at cooling and fan energy usage.