The Development and Support of Public domain Simulation Software

The transient simulation program TRNSYS was originally developed to aid in the study of solar energy systems. It was first made public in 1975 when Version 6.0 wag released. Since then it has undergone continual development, and a series of versions have been documented, released, and supported. The current version, 13.1, was released in October, 1990, and is available in mainframe, IBM PC and Macintosh formats. TRNSYS capabilities have expanded as the program has evolved: it is now used extensively for building, HVAC, and industrial process simulation as well as for solar energy system studies. TRNSYS has flexible inputs and outputs, includes a large library of standard components, is designed to be user?modified, and is extensively documented. Approximately 500 copies of the program have been distributed world-wide. The purpose of this paper is to briefly describe TRNSYS, review decisions made during the process of developing TRNSYS and to describe TRNSYS support. It is hoped that the experience gained from the development and support of TRNSYS will provide a base for the development and support of other simulation programs.