TABLE OF CONTENTS [1]
Energy requirements and fuel consumption of HVAC systems directly affect a building's operating cost and indirectly affect the environment. This chapter discusses methods for estimating energy use for two purposes: modeling for building and HVAC system design and associated design optimization ( forward modeling), and modeling energy use of existing buildings for establishing baselines and calculating retrofit savings ( data-driven modeling).
A mathematical model is a description of the behavior of a system. It is made up of three components (Beck and Arnold 1977):
Input variables (statisticians call these regressor variables, whereas physicists call them forcing variables), which act on the system. There are two types: controllable by the experimenter, and uncontrollable (e.g., climate).
System structure and parameters/properties, which provide the necessary physical description of the system (e.g., thermal mass or mechanical properties of the elements).
Output ( response, or dependent) variables, which describe the reaction of the system to the input variables. Energy use is often a response variable.
The science of mathematical modeling as applied to physical systems involves determining the third component of a system when the other two components are given or specified. There are two broad but distinct approaches to modeling; which to use is dictated by the objective or purpose of the investigation (Rabl 1988).
Forward (Classical) Approach. The objective is to predict the output variables of a specified model with known structure and known parameters when subject...
