Guide for Interface Developers — EnergyPlus 9.4

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This document is intended for developers who are creating user interfaces for EnergyPlus. It provides an overview of the essentials of the input-output structure of EnergyPlus and describes the parts of each in detail.

EnergyPlus Input/Output Overview [fig:energyplus-inputoutput-overview]

EnergyPlus Input/Output Overview [fig:energyplus-inputoutput-overview]

The diagram shown above should give the reader an overall picture of input-output in EnergyPlus. It can be seen as a linear process that includes the following steps:

1) The user enters building description (including internal space gains, HVAC arrangements, and Plant equipment properties) using the interface of their choice. In addition, the user specifies which non-default reports are desired and any optional variables from a predefined list of available simulation quantities.

2) The interface program writes the Input Data File (IDF) file, which includes the specification of any report items desired by the user.

3) EnergyPlus processes both the Input Data Dictionary (IDD) and the Input Data File (IDF) files with the “InputProcessor”. The InputProcessor uses the specifications/rules defined in the IDD and interprets the IDF raw data. The InputProcessor is really quite “dumb” and only understands a few things about each field (alpha or numeric) qualified by certain key elements in the IDD (\ comments which are discussed later).

4) Each module in EnergyPlus has one or several routines (normally called “GetInput” routines) that obtain the information from the IDF file data. These subroutines decode the portion of the IDF file that is pertinent to the local module. These GetInput routines are more context sensitive than the InputProcessor and may perform further error detection. For example, the cooling coil module may read in the coil type and its associated parameters (number of rows, tube diameter, fin spacing, etc.).

5) EnergyPlus performs the simulation elements specified in the IDF. Output is generated as a continuous stream (for the most part) and must be interpreted into a more cohesive form by output processing. The user has control over which outputs are produced and when/how often.

6) EnergyPlus produces output as required by the user into one of the output files. These files can be readily processed into spreadsheet formats for graphing and other summarizing.