Co-simulation for performance prediction of integrated building and HVAC systems - An analysis of solution characteristics using a two-body system

Integrated performance simulation of buildings and heating, ventilation and airconditioning (HVAC) systems can help reducing energy consumption and increasing occupant comfort. However, no single building performance simulation (BPS) tool o ers su cient capabilities and exibilities to analyze integrated building systems and to enable rapid prototyping of innovative building and system technologies. One way to alleviate this problem is to use co-simulation to integrate di erent BPS tools. Co-simulation approach represents a particular case of simulation scenario where at least two simulators solve coupled di erential-algebraic systems of equations and exchange data that couples these equations during the time integration. This article analyzes how co-simulation in uences consistency, stability and accuracy of the numerical approximation to the solution. Consistency and zero-stability are studied for a general class of the problem, while a detailed consistency and absolute stability analysis is given for a simple two-body problem. Since the accuracy of the numerical approximation to the solution is reduced in co-simulation, the article concludes by discussing ways for how to improve accuracy.