An ARMAX-model approach for estimating static heat flows in buildings: A method for computerised energy allocation systems

An energy cost allocation system records the energy consumption of a building and divides the overall energy costs between the flats. Because the indoor temperatures of rooms are usually not equal, static heat flows between flats cannot be avoided. Hence, in order to ensure fair energy costs per flat the system should be able to determine the static heat flows, preferably without utilising design data or in-situ measurements. This paper presents a new method for estimating static heat flows between neighbouring rooms. It also outlines the instrumentation and technical properties of the energy allocation system (EAS), needed in implementation. The approach is strictly technical, focusing only on heat transfer issues. Energy cost allocation is not considered. The approach is based on the proposed control techniques and the ARMAX-model describing dynamic behaviour of heating power. The model is created for each room/flat of a building. Parameter values are identified using real-time measurements collected from each room/flat and its environment. Only ordinary instrumentation is required. The tuning of parameters takes a few days using a fifteen-minute sampling time. A prerequisite for successful estimation is the overall control and the precise adjustment of the room temperatures at specified level. This is accomplished by the suggested set point control. All test runs are performed in a simulated office hotel using the TRNSYS simulation program. Realistic inner and outer heating loads, and their daily schedules and variations are included. The results are encouraging, but further research is needed, especially in a real building environment.