DEVELOPMENTS TO THE TRNSYS SIMULATION PROGRAM

The TRNS YS simulation program is a sequential-modular transient simul ation program which is widely used for both solar and nonsolar simulat ion studies despite its near 20-year-old origins. There have been many revisions to TRNSYS between its original release and the current vers ion 13.1 but they have maintained the same sequential computational sc heme for solving simultaneous algebraic and differential equations. TR NSYS 14 has recently been developed which implements a more robust met hod for solving simultaneous sets of nonlinear equations. The new comp utational scheme utilizes equation blocking to improve convergence pro perties and it handles discrete control decisions in a manner which pr omotes convergence in the iterative calculations. The new computationa l scheme allows TRNSYS 14 to solve problems which were either difficul t or impossible to solve in previous versions as well as backwards pro blems, 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.