The Representativity of Energy Models : A case study analysing causes for discrepancies affecting major system components and project phases when simulating energy demand

Sammanfattning: In order to clarify factors affecting energy simulations and their relation to real-world processes and results, this thesis sought to analyse how representative energy simulations and calculations are in relation to the in-use energy utilization of a building. This was done by firstly conducting a literature study which illustrate the major system components as well as project phases’ discrepancy factors. Thereafter an explorative case study was performed where the 2014 energy model was re-modelled, the building’s in-use energy utilization and discrepancies were audited, followed by a mapping of the mentioned discrepancies to identified factors. Major findings within the study were that the simulated total energy use was representative of the audited energy use intensities, however the division of subsystem energy use was not. Discrepancies causing this gap between model and reality affected all major energy components as well as phases. The representativity was affected by in-built factors, lack of integration of system design revisions and a lack of knowledge regarding e.g. tenant behaviour when simulating the building. Furthermore, faults and issues which arose during system installation and operation were identified. Lack of data from the in-use system further widened the gap between model and reality due to the assumptions and simplifications needed for the in-use system evaluation. Regarding the representativity, as there is no definition for the term, it is impossible to conclude exactly how representative the model was. The final result is that it can be said that the original model was partly representative, while a comprehensive re-simulation implementing all intentional discrepancies, including both input changes as well as energy system revisions, rendered the most representative result. Further, there were five process improvements described in order to improve representativity throughout the project process; 1) Model the system as extensively as possible, do not oversimplify units, 2) Note “invisible” input data, 3) Use iterative modelling to ensure representativity by implementing the final system design and simulating, 4) Ensure a greater utilization of the designed system, such as installing all specified meters and logging data properly, as well as 5) Define key numbers related to meters and units and present these under a specific heading in the energy report in order to decrease discrepancies, increase measurement data and ease analysis of the in-use system.