Paper Conference

Proceedings of eSim 2022: 12th Conference of IBPSA-Canada


An Analysis of the Hybrid Internal Mass Modeling Approach in EnergyPlus

Zhelun Chen 1, Jin Wen 1, Steven T. Bushby 2, L. James Lo 1, Zheng O'Neill 3, W. Vance Payne 2, Amanda Pertzborn 2, Caleb Calfa 3, Yangyang Fu 3, Gabriel Grajewski 1, Yicheng Li 1, Zhiyao Yang 3
1 Drexel University, United States of America
2 National Institute of Standards and Technology, United States of America
3 Texas A&M University, United States of America

Abstract: Accurate simulation of building system dynamics is particularly important for understanding building energy flexibility. Among all dynamics in a building, a zone temperature’s variation is especially important, as it significantly affects a building’s electricity load profile when its heating, ventilating, and air conditioning (HVAC) system is controlled with on/off cycles or setpoint reset strategies. To accurately simulate a zone temperature’s dynamics, internal mass needs to be modeled carefully. In this paper, we compare the two internal mass modeling approaches provided by EnergyPlus, i.e., internal mass object and zone air capacitance multiplier, to better understand their impacts on zone temperature simulation. Real building zone temperature dynamic data from small- and medium-sized office buildings are analyzed and compared with simulated data. In particular, we illustrate the effectiveness of a hybrid method of the two EnergyPlus modeling approaches, especially when the zone is conditioned with heat pump systems with on/off cycling.
Keywords: internal mass modeling, EnergyPlus, air heat balance, HVAC simulation