An improved computer code for the simulation of solar heating systems

Abstract

A generalised solar energy simulation code, which represents a significant improvement over fixed step iterative simulation codes, is presented. The key features of the code are the simultaneous solution of all differential equations arising from closed loops in the system, and the technique for advancing the simulation from “control function” to “control function”. Computer time is minimised by the use of sparse matrix techniques together with automatic time step control generated from an error bound estimate. The application of the improved code to the simulation of solar energy systems is demonstrated on two example problems. In the first problem, emphasis is placed on predicting the temperatures of the fluids within the system and the controller actions, while in the second problem the emphasis is on predicting long-term system performance. The simulation results of both these problems demonstrate that the improved code is suitable for both detailed system control and long-term system performance studies.