Full Description

To predict the energy requirements of a building environmental system, a simulation of the system must be performed. In most cases, the system is simulated by means of a computer program; the input to this simulation is information of the momentary heating and cooling loads from various zones or spaces within the building. The output is the calculation of fuel or energy requirements of the system at that time.

There are probably several hundred different energy programs in operation, varying in sophistication from extensive ones requiring large computers to streamlined ones that serve for the initial screening of mechanical systems. We believe that both the sophisticated and the streamlined programs have their place; but regardless of its size the level of sophistication of the computer program should be uniform throughout. For example, it is inappropriate tomake a very refined load calculation entailing elaborate input and precise definition of building properties and consuming large amounts of computer time, if the output of this section is fed to a crude system simulation. If the program developer accepts the concept of uniform sophistication, he is still faced with the question of the magnitude of errors introduced in the system simulation by taking certain shortcuts.

The ASHRAE Task, Group on Energy Requirements for Heating and Cooling of Buildings has developed preliminary procedures for simulating systems.1 The Task Group has proposed procedures that are as accurate as our present knowledge permits, but has also assumed the responsibility of suggesting how to simplify system simulation procedures with a minimum sacrifice in accuracy. Under the supervision of the Energy Task Group, ASHRAE has sponsored a research grant, RP-131, that primarily covers the cost of computer time to conduct the study reported in this paper. The project is titled, Preliminary Sensitivity Study of Procedures for Simulating Systems for Energy Calculations, and the details are presented in Refs. 2 and 3. This paper summarizes the investigation's conclusions.

Citation: ASHRAE Transactions, Volume 79, Part 2, Louisville, KY