Numerical investigation of a CO2 cooling system connected to Spawn-of-energy-plus thermal zones

Abstract

Today, only about 25 % of the European building stock is considered energy efficient. Meanwhile, the implementation of CO2 as a refrigerant is considered one of the solutions to improve the overall building’s energy performance, especially if the heat recovery concept is applied. In the current study, a detailed dynamic simulation model of a CO2 chiller connected to the American Department of Energy reference small office building represented via Spawn-of-EnergyPlus is investigated for three different weather conditions in Chicago, Oslo, and Athens and two scenarios with heat recovery and without heat recovery. Three Modelica libraries of the thermal systems from TLK-Thermo GmbH, Modelica standards, and Modelica Buildings were used to develop the models. The simulation was executed on Modelica/Dymola simulation platform, and it lasted for five days. Results demonstrated that in the scenario with heat recovery, the system COPs are improved to 4.9, 5.4, and 7.2 from 2.2, 2.9, and 5.3 for Athens, Chicago, and Oslo, respectively.