Steady state modeling and simulation as applied to energy optimization of a large office building integrated HVAC system

The International Business Machines Corporation (IBM) constructing a million square foot, 44 story office building in New York City, New York. The building design includes an integrated heating, ventilation and air conditioning (HVAC) system allowing several system configurations. Sophisticated energy optimization techniques will be implemented in the building's HVAC system. Toward this end, a steady state simulation of the building HVAc system was developed in order to study the interactions between the various energy consuming pieces of equipment.

Semi-empirical models were chosen to represent most of the individual pieces of equipment in the HVAc system. Each of these models is based on general engineering principles and contains several adjustable parameters. Using a nonlinear regression technique, the ad justable parameters can be determined in order to fit equipment performance data. Semi-empirical component models were developed and test r results are presented for psychrometric calculations, cooling towers, chillers, cooling and dehumidification coils and airiwater induction units.

In some cases empirical models were chosen to represent an individual piece of equipment when a semi-empirical description was not practical or justified. Empirical models of fans, pumps and piping and duct system characteristic curves were developed using low order polynomial functions.

The study of global interactions and more specifically, optimization of the overall energy usage in a large building requires tying together the individual HVAc component models into large-scale system simulation. This 3 process of coupling the component models is accomplished using material and energy balances. In order to exemplify the development of a large-scale HvAc system simulation, the routines used to describe the IBM Building air systems are discussed in detail. In addition, simulation results are presented for various load and outside air conditions.