Next-generation energy modeling

Since 2001, the DOE has released the energy modeling calculation engine called EnergyPlus as a new generation flagship tool meant to combine the best features of the multiple previous tools funded through the federal government.

Erin McConahey, PE, Arup, Los Angeles

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Since 2001, the DOE has released the energy modeling calculation engine called EnergyPlus as a new generation flagship tool meant to combine the best features of the multiple previous tools funded through the federal government. In the past, the DOE has generally released a public domain engine and allowed third-party developers to create interfaces; however, there has been limited uptake as the more familiar DOE-2 based software is still generally acceptable for energy code compliance. Therefore, the DOE and the California Energy Commission have invested in the development of a new graphical user interface called “Simergy” to be released to the public in late 2012 with the intention that the interface will be so user-friendly that it will help to greatly increase the ease-of-use accessibility of energy modeling for the industry.

Editor’s note: The author has been on the beta testing team for Simergy and has been given permission to include a preview of the new software in this article. The software design team at Lawrence Berkeley National Laboratory has engaged with HVAC and architectural industry professionals for the past five years to develop interfaces that allow the easy and quick generation of models. Time-saving features include the following:

• Pre-set building geometries in the rectangular, L-shape, U-shape, H-shape, T-shape, and cross-shape configurations are available with automated zoning of perimeter versus interior as per best practice energy modeling in less than a minute, inclusive of automatic unique space naming. In the first release, there are additional freeform tools available to import *.dwg files and trace over them to create building geometry, and eventually it should be possible to import whole BIM models to create geometry. All auto-generated zoning is visible in a BIM embedded within the program for visual cross-reference. (See Figure 4.)
• The use of drag-and-drop techniques to create thermal zone groupings allows the wholesale assignment of internal load, temperature control, and building construction templates.
• Similarly, the use of drag-and-drop HVAC components into airflow and water loop system templates allows the user to exactly match the component order and control intention of the original design.

In addition to these process optimizations, access to the EnergyPlus engine itself opens the doors for an engineer to model natural ventilation, thermal mass, chilled beams, underfloor air distribution systems, thermal stratification, radiant floor systems, ground coupled heat exchange systems, renewable energy devices, and thermal storage devices, along with the pre-set “template” examples for the more traditional HVAC systems.

Software packages

The most prevalent commercially available energy modeling software packages are: