Real-time 3D Animated Simulator and Energy Analysis
Real-time 3D Animated Simulator
Learn HVAC is an interactive tool designed to introduce fundamental HVAC concepts to students.
The concepts of HVAC operations come alive by the presentation of real-time 3D animations of the detailed, accurate simulation of a simple HVAC system. The real-time animated simulations permit the user to observe the dynamic performance of HVAC control systems responding to the changing HVAC system and its components. Users can view the HVAC system operating normally, or with one or more "faults" activated.
Students can move through the 3D animation/simulation, viewing each system component as it operates. These components -- the filter, economizer, heating coil, cooling coil, fan, VAV box, diffuser, occupied space, and so on -- visually change according to user inputs and in response to second-by-second simulation calculations. Air particles change color. Water flows through the coils.
Behind the user interface, Lawrence Berkeley National Lab's (LBNL's) HVAC component models, running on LBNL's SPARK equation solver, crunches the numbers, updating the simulation every few seconds with realistic data. As the student changes input data, or activates one or more "faults," the SPARK models adjust the output variables accordingly.
There are over 200 HVAC variables used within the SPARK component models to control the system's performance. Changing the defaults for these variables will adjust the system's behavior and can thereby create different educational situations. To make this customization process easier, Learn HVAC comes with a companion "Instructor Tool" web site that allows instructors and administrators to create learning "scenarios," complete with movies to add contextual clues.
Learn HVAC builds upon a basic simulation/animation functional capabilities developed under a multi-year NSF grant to Laney College. The software team for that effort was a collaboration of The Deringer Group Inc (TDG) , LBNL, with strong assistance from McQuillen Interactive and Killer 3D.
The Learn HVAC tool uses videos and other information to present problem situations, which will facilitate understanding of the operating principles of HVAC system components. This tool allows users to diagnose basic equipment problems at the component and system level.
SPARK simulations
SPARK is a sophisticated equation-solving software package developed at Laurence Berkeley National Lab. One of its uses has been to simulate the detailed operations of HVAC systems, components and their controls. For the Learn HVAC CBE simulations, a number of component models have been created by LBNL that use the SPARK equation-solving capabilities to describe an air handling system and with a series of interacting typical components.
When a scenario is started, the SPARK simulation is not automatically started. The user clicks a button on the screen to start and stop SPARK. Once the user starts the SPARK simulation, the screen comes to life with second-by-second 3D animations and operations data. The user can stop SPARK, change input variables to get a different effect, and then start it again.
The simulation normally runs much faster than real time, so that the user can quickly observe system behavior changing over time. The current “normal” setting is for the simulation to run 100 times faster than real time. The user can change this relative speed.
3D Animation Engine
Learn HVAC uses a 3D animation engine that has been developed in Flash ActionScript 3.0. The engine presents 3D animations of colored air and water superimposed on 3D images of the HVAC system and its components. Water moves through pipes and air particles move through the ductwork and into the room and plenum. Fans spin and dampers move according to the system status.
The animations do require a certain level of processing power (an average desktop or laptop purchased in the last few years is usually fine). For less powerful PCs, the animations may become jerky and the system may bog down. This was a problem on older versions of the software that used Flash 8 and ActionScript 2. In the latest versions of Learn HVAC, the animations now run several times faster and much smoother because of the significantly improved performance of Adobe Flash 9, and ActionScript 3. Still, if there continue to be problems with older slower PCS, Learn HVAC does have the option, however, to scale back or turn off the animations to accommodate earlier machines. A popup "Performance" dialog box allows the user to modify several system performance parameters.
Graphic User Interface (GUI)
The user can control all program actions via a GUI. The GUI is built in Flash and is based on the ARP framework; it provides a seamless environment for viewing different portions of the HVAC system. Input variables are easy to access and update. Output variables appear at the bottom of the screen and can be graphed against each other.
Inter-process communication
Every few seconds the user interface and the SPARK simulator communicate with each other. If the user has changed any inputs they are sent to SPARK, while SPARK output variables are collected and used to update the user interface. These output values drive the animations, information displays and charts.
Faults
An important part of Learn HVAC is that a user can view the HVAC system either operating normally or operating with one or more "faults" activated that can cause the system to operate outside of normal conditions. Many faults can be activated to varying degrees, using "sliders." Often the HVAC system or component being impacted by a "Fault" can adjust to the fault with little or no symptoms or negative impact until some threshold condition has been crossed. To date some 20 faults have been implemented and are available for users to activate. Another 50 or so faults are planned to be implemented in the future.
When a scenario is started, the user can interact with the animated simulations in one of 3 basic ways. The user can:
- View normal operation: The user can observe the system behaving normally, with no faults activated. The software parameters can be set to ensure that no faults are inadvertently activated. Thus, a user can be comfortable that the operation being viewed is indeed "normal" for the season, time, occupancy conditions, and other initial settings.
- Activate known faults: The user can activate one or more known faults to mild or severe levels and can observe their impacts on system behavior. This is an excellent learning mode of use.
- Troubleshoot a Scenario with unknown faults: An instructor can create scenarios with single or multiple faults that are hidden from the user. In this case the challenge to the student is to find the faults and to propose corrective action. Instructors will often group students into teams to do the troubleshooting. Such Problem-Based Case Study (PBCS) Scenarios can be relatively simple and be solved quickly, or can be difficult and complicated, and might take a team one or more weeks to solve.
Energy Impacts
The real-time animated simulator described above provides close-up snapshots of dynamic system behavior. However, it does not provide longer term result such as monthly or annual performance summaries. Such information is now being provided by parallel analysis of the energy impacts of HVAC operation over diurnal, monthly and annual time periods. These energy analysis features were not included in the products developed under the NSF grant, but are new additions added as a result of collaborative CEC funding. These new features are summarized below and are described in more detail elsewhere on this web site in the tab on "Using Learn HVAC."
Energy impacts has been added to Learn HVAC in several ways:
- New variables has been added to the SPARK component and system level models.
- Use cases, and user options and interactions have been expanded
- The ability has been added to store and retrieve user-generated energy and simulation data.
- Data structures are being expanded to permit examination of 5 zones on a floor.
- An education-focused implementation of the EnergyPlus simulation tool has been added to Learn HVAC
- Comparative charting of results.
- New component models for energy conversion equipment has been added - boiler, chiller, cooling tower
New variables added
A number of energy-related variables have been added to the Learn HVAC system variables. [To be expanded.]
Expanded Use Cases
In the previous versions of the software, the user could view and interact just with the short-term, real-time animated simulations. Annual or monthly longer-term analysis were not available.
The current version of Learn HVAC now includes both short-term and long-term analysis options. The long-term analysis is provided by one or more simulations using EnergyPlus. The energy impact options are as follows:
- When a scenario is created, an EnergyPlus (e+) annual simulation is run for key building features that correspond to the conditions of the scenario. The e+ zone loads for the initial time of the scenario are used to generate the input loads for the SPARK short-term animated simulation. The EnergyPlus input file and selected outputs are saved with the scenario by Learn HVAC.
- When a user selects and activates an energy-related scenario, the EnergyPlus I-O file is copied to the user's directory.
- The user can modify the real-time, short-term inputs and faults as before.
- Then, with the new, energy-related variables, the user can make changes to impact energy use, peak demand, and HVAC operations.
- The user can request a second long-term comparison EnergyPlus (e+) simulation. This will use the basic I-O of the fist simulation, but will incorporate the changes made by the user in using the short-term animated simulation.
- The user can compare the original and revised e+ results as well as the original and revised SPARK simulations.
Users are still free to use just the original use case with the short-term 3D animated simulation and no energy analysis.
Storage and retrieval of user I-O data.
Previous version of this CBE tool allowed for storage and retrieval of Scenarios downloadable for an instructor site. However, a student user could not store and retrieve data files. This has changed in the current version of Learn HVAC.
A key objective in this current version is to allow a user to compare the energy efficiency of a current set of HVAC conditions to a previous (initial) set of conditions. In order to allow such comparisons, this new version now allows students to store and to retrieve at least a limited set of user data. The current version, when completed, is expected to allow one comparison per user per scenario. Future versions should allow multiple comparisons per user per comparison. [To be expanded.]
Data Structures for 5-zone analysis
The previous versions of this software presented analysis for a single zone. The current version of Learn HVAC is being designed with a data structure to permit examination of any one of 5 zones (North, East, South, West, Core) on the chosen floor (top, medium, or ground) of a building. This will allow users to switch from zone to zone in analyzing HVAC system performance. For example, HVAC behavior at 3 pm on a sunny summer afternoon can be expected to vary considerably by zone.
However, while the data structures will be developed at this time, the user interface elements, 3D models, and transitions are not included in the current CEC funding, and will need to wait for future funding.
EnergyPlus within Learn HVAC
A user of Learn HVAC can easily activate comparative annual EnergyPlus simulations. Our EnergyPlus implementation is limited toward specific education objectives. We use a large office prototype file, developed at LBNL for US DOE. This prototype has extensive imbedded "macros." Learn HVAC also expands upon a user front end to EnergyPlus that was developed by LBNL as part of a demand-response application. This results in an easy to use Graphic User Interface front-end that allows a user of Learn HVAC to specify key building features of interest. The user can quickly select:
- Climate location (and its associated weather file).
- Building configuration, orientation, and key window features.
- Zoning.
- Key internal loads by zone.
All other building inputs are defaulted, using the rules imbedded in the prototype macros.
When ready, the user clicks a button to run EnergyPlus. An example run is shown below with a DOS popup panel showing progress. This capability is currently working in draft form, but needs refinement.
There is great potential for expanding this computer-based education (CBE) use of EnergyPlus within Learn HVAC. Future version may have expanded capabilities - daylighting, electric lighting, building envelope, alternate HVAC systems, etc.
Comparative charting of results
Results variables from EnergyPlus or SPARK simulations can be selected and charted using "drag and drop" techniques. Currently, charts can be either time series or XY. An example set of charts is shown below. these were generated from the EnergyPlus simulation results shown in the graphic above. In developing this capability the Learn HVAC software team is making use of techniques forged under another collaboration with LBNL for CEC. That effort produced a proof-of-concept prototype of visualization concepts. See www.viztool.org.
New SPARK Component Models
New component models for key energy conversion equipment are being added to Learn HVAC. These include component models for a boiler, chiller, and cooling tower. Draft 3D models of these new components are shown below. These models are now included in the navigation panel for the public version of Learn HVAC, but there is not yet any simulations behind the 3 new models shown. The SPARK component models for these are now being developed.
