Conference Year



Refrigeration, OpenStudio


OpenStudio, developed at the National Renewable Energy Laboratory (NREL), is a cross-platform collection of simulation tools for whole building energy modeling. EnergyPlus and Radiance are the primary simulation engines in OpenStudio and the latest addition is a collection of refrigeration objects developed at the Oak Ridge National Laboratory (ORNL) which makes the refrigeration system components of EnergyPlus available for use through OpenStudio. This paper highlights the benefits of including refrigeration modeling functionality in OpenStudio, the object model, the exposed Application Programming Interface, and discusses some of the design challenges faced. The project was implemented in four phases with each phase focusing on one aspect of the software. An initial set of EnergyPlus refrigeration components were selected and implemented, following which, additional components in decreasing order of priority were implemented. An Agile software development philosophy was employed along with modern source control tools such as GitHub. During the initial design, six main refrigeration components were determined to be critically important. These were Refrigeration System, Compressor, Display Case, Walk-In, Air-Cooled Condenser and Secondary System. Scripts were used to automatically convert various objects from the EnergyPlus Input Data Dictionary (IDD) file into C++ code. These prototypical source code files for the refrigeration objects were then modified to allow full instantiation of the objects. The objects, complete with their unit tests, were then submitted for integration into the main development branch of the software. During the second phase, the following components were implemented: Mechanical Subcooler, Liquid-Suction Subcooler, Cascade Condenser, Evaporative-Cooled Condenser, and Water-Cooled Condenser. During the third phase, the remaining refrigeration components from EnergyPlus were added: Air Chillers, Transcritical Refrigeration System, Transcritical Compressors, Air-Cooled Gas Cooler and waste heat recovery using the Air Heating Desuperheater Coil or the Water Heating Desuperheater Coil. In addition, EnergyPlus comes with metadata information of hundreds of refrigerated display cases and refrigeration compressors. These were added to the U.S. Department of Energy’s Building Component Library (BCL), which is a comprehensive online digital library of various building blocks of an energy model. During the fourth and final phase, documentation of the developed Application Programming Interface was created. In all phases, close collaboration with multi-lab partners was maintained who provided extensive support and developmental feedback to the ORNL team. It is expected that the addition of these refrigeration components fills a gap and will enhance the successful adoption of OpenStudio as a modeling tool of choice in the buildings simulation community. Furthermore, it is hoped that these refrigeration capabilities will allow retailers to assess the energy impact of a variety of supermarket and distribution facility refrigeration system design options and aid in the selection and implementation of energy efficient systems.

2566_presentation.pdf (3421 kB)
Refrigeration Modeling Components in Open Studio