The TRNSYS simulation program is a sequential-modular transient simulation program which is widely used for both solar and nonsolar simulation studies despite its near 20-year-old origins. There have been many revisions to TRNSYS between its original release and the current version 13.1 but they have maintained the same sequential computational scheme for solving simultaneous algebraic and differential equations. TRNSYS 14 has recently been developed which implements a more robust method for solving simultaneous sets of nonlinear equations. The new computational scheme utilizes equation blocking to improve convergence properties and it handles discrete control decisions in a manner which promotes convergence in the iterative calculations. The new computational scheme allows TRNSYS 14 to solve problems which were either difficult or impossible to solve in previous versions as well as backwards problems, for which the output of a component is specified and the input must be determined. The computation scheme incorporated into TRNSYS 14 is described in this paper and its capabilities are illustrated with several examples.

Issue Section:
Research Papers
Topics:
Simulation, Algebra, Computation, Differential equations, Nonlinear equations, Solar energy, Transients (Dynamics)
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Klein, S. A., et al., 1975, T “TRNSYS—A Transient System Simulation Program “User’s Manual,” Solar Energy Laboratory, University of Wisconsin, Madison, WI.
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