DOE’s building energy and controls modeling software targets advanced controls, district systems, grid integration

by Brianna Crandall — August 25, 2021 — The U.S. Department of Energy’s Building Technologies Office, the Lawrence Berkeley National Laboratory and the National Renewable Energy Laboratory, in collaboration with Modelon and Objexx Engineering, have released the initial version of the Spawn of EnergyPlus energy modeling software. Spawn is not a replacement for EnergyPlus, at least not in the foreseeable future, says BTS. Although it does perform whole-building energy simulation, it targets new use cases in advanced controls, district systems, and grid integration.

DOE Spawn of EnergyPlusSpawn supports these new use cases by making fundamental use of coupled simulation via the Functional Mockup Interface standard. Spawn reuses the weather, envelope, lighting, and loads models from EnergyPlus and packages them as a single model. However, it replaces EnergyPlus’ traditional, imperative, implicit, load-based heating, ventilation and air-conditioning (HVAC) and controls models with explicit declarative state-based models from the Modelica Buildings Library that are translated and automatically linked with the EnergyPlus model.

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By combining models in different configurations, Spawn is able to simulate either a single building or a collection of buildings linked by shared thermal, electrical and control systems.

Spawn also fundamentally leverages the Modelica, a standard for equation-based modeling. The use of Modelica to model HVAC and control introduces capabilities that are not found in traditional energy simulation engines such as EnergyPlus. The most significant of these is the ability to simulate physically realistic control sequences using the same specification that is used in controller implementations. The ability to use a single control specification for both energy simulation and implementation aims to bridge these traditionally separate domains and promote the use of high-performance control sequences, explains BTS.

Modelica also enables modeling of novel HVAC and district system components and configurations. Spawn HVAC and control models have been developed as part of a multi-year international effort led by IEA EBC Annex 60 and IBPSA-World Project 1 to develop Modelica models for building and community systems.

This initial version of Spawn modeling software is available for Windows and Linux as part of release 8.0.0 of the Modelica Buildings Library. This initial version is not packaged with a simulation or model development environment. Instead, users can use a number of commercial or publicly available tools as detailed on the download page.

The team is working to enable Spawn to leverage a number of Modelica simulation and editing platforms as well as to package Spawn with a Modelica compiler at no cost to Spawn users. Other active developments include new models for radiant systems, numerical methods for simulation of large systems, and HVAC and control templates.

A longer, more detailed version of this announcement has been published as a blog post. Visit DOE’s Building Energy Modeling sub-program page for more information about Spawn and other projects.