Making Realistic Predictions on Building Energy Performance through Coupled Energy Simulation and Computational Fluid Dynamics

Abstract

Buildings account for nearly 40% of the global energy consumption and hence presently high emphasize is made on improving the energy performance of buildings. Energy Simulation (ES) is the most widely used method in predicting the energy performance of buildings during the conceptual stage. However, it is observed that Energy Simulation tools show certain inherent deficiencies in predicting the energy performance of buildings. The said tools do not have the capacity to model air circulation through the building space explicitly. Energy Simulation tools mainly rely on the simplifying assumption that air within a thermal zone of a building is well-mixed. Furthermore, convective heat transfer coefficients of building surfaces are calculated using set empirical correlations. Hence, ES tools often find it difficult to make realistic predictions on energy performance of buildings. The literature also reveals that most Energy Simulation tools under-predict energy consumption in buildings, especially under sunny conditions. On the other hand, Computational Fluid Dynamics (CFD) tools are capable of predicting the indoor flow field comprehensively. However, CFD simulations need to be provided with the corresponding boundary conditions of the computational domain, which are readily available in the Energy Simulation approach. On this basis, the paper explains how Energy Simulation can be coupled with Computational Fluid Dynamics in predicting the energy performance of an actual building design more accurately through complementary data exchange between the tools. The analysis uses EnergyPlus 8.0 and Ansys Fluent 6.3 as the tools for conducting Energy Simulation and Computational Fluid Dynamics respectively. MATLAB R2012a establishes the coupling platform. The study shows that the coupled scheme predicts considerably higher energy consumption for the building design compared to that given by the conventional Energy Simulation using EnergyPlus.