Bentley AECOsim Energy Simulator Preview

Alan Jackson bio photo By Alan Jackson Comment

Contents

I recently had the chance to get my hands on a second beta version of Bentley’s new AECOsim Energy Simulator for building simulation. The version I tested was v08.11.07.78.

The first time I had a chance to see AECOsim was at the ASHRAE BEM Conference where it was demonstrated by Dru Crawley. Soon after I received the first Beta which was not at a good state for review. This version however is at a point where it is worth previewing.

The overview of the interface is that it is built into the Bentley Microstation platform offering a familiar CAD style interface with various 2D and 3D views for model creation. Right and Left click methods and tool bars will be familiar to Microstation users, but maybe not for others. A ribbon style main toolbar now part of most modern .NET Windows applications is also available in the interface to organize the various built-in utilities and menus.

I only used the application for a short period of time, so it is possible my review may touch upon areas that I did not fully understand, in which case I will update this post should I find anything was incorrect due to my inexperience.

Keep reading below for my full review.

I will walk through a typical model workflow and highlight the implementation of the following features:

  • Defaults and Template Management
  • Materials and Construction Editor
  • Schedules
  • GBXML Import
  • Geometry Creation
  • Zoning
  • Weather Files
  • ASHRAE Baseline Creation
  • HVAC Systems
  • Steady State Calculations
  • Simulation and Reports

Defaults and Template Management

The available libraries for your project are handled through the Data Manager tab where you have the ability to pull in systems templates for your project and modify the project defaults and templates if needed. The defaults manager allows you to enter project wide defaults for items like building constructions such as exterior walls, as well as the default wall and window heights. An extensive library of typical constructions are available as well as predefined ASHRAE 90.1 constructions for baseline models. While these settings are global, you also have the ability to break down default construction types for certain room types, or edit it manually at the instance of the surface.

Materials and Construction Editor

In addition to the default library, you also have the ability to define constructions yourself using the material library database, or again by creating custom materials. The interface for creating constructions is very slick allowing you to pull in materials and define the construction thickness, as well as an extensive amount of other parameters. Constructions are categorized by their appropriate surface location, ie. wall or roof.

Schedules

The schedules manager is organized in a familiar manor allowing the definition of specific day schedules for temperatures, occupancy etc. where the individual hour values are defined. Below hourly you can apply those schedules to the days of the week and then define weekly schedules to the entire year. Those familiar with schedule management will have no problems here. And extensive library of default schedules is also made available to the user again, to get up and running quickly. The nice part of this is that the entire yearly schedule is handled all within a single window so you don’t have to switch back and forth between your day and week schedules like we have to in eQuest.

GBXML Import

GBXML, for better or worse, has become the industry standard for file transfer when it comes to building simulation software. I was pleased to see that the import feature worked very well. It seems that the limitation in GBXML now is more about how clean the exported model is rather than how clean it gets imported. At least that is the case with AECOsim. Any anomalies in the geometry or zoning was clearly a function of the way it was exported, as I was able to resolve most of the issues within the exporting platform, in this case I used Revit Architecture. Walls, windows and roofs as well as room names all came across with no issue. Construction definitions will be pulled from your default templates so it is a good idea to have those set up prior to importing, though the Global Changes tool comes in very handy when you need to make large changes to the information of the entire models, specific zones or individual sections of rooms. If your company has a work flow for using GBXML files, this feature could be a key selling point.

Geometry Creation

Those of use not utilizing the GBXML model import feature will still have a fairly easy time creating models from scratch. Because the interface was written on top of the Microstation platform it allows the importing of pretty much any CAD format (.dwg, .dgn, .dxf, etc). One of the cool features is the auto-detection of embedded room information in the CAD formats. I’m not completely familiar with this but it appears many modern BIM/CAD platforms have built-in room definitions by boundary, so if you have this implemented you can just click on a room and it will auto create the volume based on the room boundaries and the defined room heights used in your defaults or the toolbar. Additionally you can use the tried and true method of tracing out the room boundaries snapping to CAD or by freehand. During the room creation process you can define the default information pulled from the templates by room type, so you can specify the room is a conference room upon creation or you can go back and define it later.

Window creation is also a breeze. First you select the room then you just draw a line along the wall indicating the length of the window, again default heights and sill heights are brought in from your template or you can override them during window creation. If the windows are already outlined in your CAD plan view, defining them is very easy.

Floors are created automatically, as well as ceilings, with ceiling plenums being created if needed by specifying a partition height lower than your wall height in the Defaults Manager. Example, a 12 ft. wall with a 9 ft. partition height will yield a ceiling plenum of 3 ft. and this is created automatically when defining the room. One downside here is that there is no override on room creation for removing the ceiling. The only way I found was to change the setting in the Defaults Manager. Also, if no zone is above the room a flat roof will be created for you also, although there is a separate roof creation tool for additional roof definitions or for sloped roofs.

Zoning

Zone management is handled under the System Managers tab. Zoning allows you to do exactly what you think it would do. Group rooms together to form zones for combined HVAC simulation but also to apply settings and templates across a group of rooms quickly. HVAC is applied at the zone level when we get to that stage. This is a nice feature that allows you to bring rooms across and treat them individually but still group them together as a thermal zone. Not much more to say about this. Behaves similar to Zone Lists in Energyplus.

Weather Files

AECOsim handles your standard Energyplus EPW weather files, but also comes packaged with an extensive list of Meteonorm weather files. The interface for weather management allows you to modify peak design day values at the project level if required and also modify the actual hourly values. A nice feature is the graphical plot of the weather information at the bottom. Projects can load up with multiple weather files if needed.

ASHRAE Baseline Creation

This could be a killer feature if it proves to work well with little post processing required from the end user. As guessed you have the ability to take you design case model and have AECOsim generate the baseline model for both ASHRAE 90.1 2004 and 2007, plus the necessary rotations. Theoretically this makes all the necessary modifications to comply with the Appendix G guidelines, such as material constructions and HVAC systems and efficiency. I did not have a chance to check all values and settings for the baseline model, but it does indeed work as expected and I imagine Bentley will be sure that it meets all required measures for submission to rating authorities and code compliance jurisdictions. This is not the first time we have seen this feature and it looks like it is becoming a requirement to compete with other Building Simulation tools on the market. Both IES and I believe the latest version of eQuest have similar functionality although I have not tested them.

As a bonus there is also a ASHRAE 62.1 compliance check that calculates the required outdoor air for each space and determines based on the design information in the model whether or not you are in compliance with ASHRAE 62.1 2004 or 2007. The report that is generated likely will be all that you need if your are shooting for LEED which makes ASHRAE 62.1 a prerequisite requirement. This tool could come in handy. Lets hope that similar tools make it into all our building design tools, as this calculation can be a pain when mixed air systems are designed in the project. DOAS FTW!

HVAC Systems

This is really the bread and butter of building simulation tools. Many people turn to Energyplus for its vast HVAC systems library and ability to create custom systems through various use of available HVAC objects and loops. One of the main gripes with Energyplus is that it is difficult to create and manage your HVAC systems if they fall outside of the HVAC Template library. The good news with AECOsim is that standard systems seem very easy to create and manage. Most of being automated through the available systems library which for the most part covers the Appendix G systems. Modifications to individual elements such as loop set-points and efficiency curves are editable through the HVAC Manager interface. It appears that you can also create custom systems through a drag and drop nodal interface similar to TRNSYS allowing you to interconnect various HVAC objects. This is an area I will have to look into more as it is not very intuitive and may take some training or a good read through the documentation to truly understand its capabilities. It doesn’t appear you get the much desired ability to drag and drop AHU components in to create systems, but perhaps that will come with the final release as it was shown during the demo at the ASHRAE Conference. Regardless, the HVAC Manager does take a substantial amount of the painful system management nightmare Energyplus users are accustom too and makes for an easier way to handle your systems while still not losing any of the complex customization power users are looking for.

Steady State Calculations

This is another stand out item that differentiates AECOsim, and a feature that many users have long been asking for from the Energyplus Development team, the ability to do your steady state peak load calculations from within your building simulation software. It is such a tremendous feature to have because it lets the designer/engineer keep all there information contained in one platform which is a big plus for those of use who struggle with the a Swiss Army knife of building simulation and analysis tools. The calculation methods available are ASHRAE RTS, CIBSE Heat Gain, and CIBSE Heat Loss (Simple and Basic). There is also a Psychrometrics utility that provides information on the state points for various system node points. I didn’t get a chance to use the psych feature extensively. An item worth noting when it comes to calculation, and this is true in many instances within the application is the ability to “dig down” into the calculations. So for example you notice the cooling load is extremely high in a particular room, you can double click on the load sum and continue to get finer grains of detail as to the individual factors to the peak loads allowing identification for error or areas for improved design.

Simulation and Reports

The simulation window is fairly straight forward, and at this point it should be you just want to get your results! You have the ability to select which buildings to run which includes at this point our design case as well as your baseline buildings and rotations. You can choose to simulate all buildings, individual building and even individual zones if you would like to examine energy use for a specific portion of the building. You also get to choose the weather file and the time period for which to run the simulation, so the whole year or maybe just a summer week if desired.

Conclusion

Overall the pros outweigh the cons for AECOsim. Bentley managed to hit few key points that may make this application very appealing to customers. The first being with the inclusion of peak load calculations. This feature allows customers to have a cohesive design and simulation tool where there is no need for additional 3rd part software for peak loads. For Trane Trace users this was one of the reasons they chose to stick with Trace 700 for their loads and energy modeling. A one stop shop. It seems clear that Bentley is going after these users showing customers they can drop their old loads software and move to a single platform. Another key area is the fact that Bentley managed to, for the most part, completely hide Energyplus from the end user. There were no IDF edits that I could see anywhere in the application yet they still managed to keep all the functionality and flexibility available for hard core Energyplus veterans. This along with 90.1 baseline model automation and 62.1 validation makes for a very well rounded debut for AECOsim in the BEM arena.

Now for the areas where Bentley missed the mark. While the program is sprinkled with some good visual feedback line graphs during certain tasks, it seems the overall appearance of the reporting of results is lacking. I could not find visually appealing summary reports for the simulations that would be nice to include in LEED documentation or for client presentations. Ultimately you get something not much more thrilling than the HTML reports we are used to from Energyplus. While hiding IDFs from users may be a plus for some users, many will not be happy that it seems at the moment there is no way to import or export existing IDF files. It would seem this is not a big deal, I mean, who wants to deal with IDFs anymore after moving to this program. However, this next point is why its a problem for me. Where is the scalability! The program seems to target only those users who are well on their way through the DD phase of design. There is no inclusion of conceptual modeling at all in the program. eQuest users who enjoyed scaling a project from SD through CDs by way of the Wizards and Detailed Edit mode will be disappointed. And for users, like me, who enjoyed starting a project in Energyplus File Generator (soon to be Model Maker) or OpenStudio will come to see why the lack of IDF import could be a deal breaker.

Ultimately though, customers who are looking to move beyond the .. dare I say .. deprecated, DOE2 platform. In hopes of moving to the more modern Energyplus engine for its flexibility and comprehensive systems capability, should be pleased with this offering. It has the features to get you from start to finish with little hassle, and that may just be enough for the masses.