Master's Thesis Laura Maier
Integration of heating energy system structures into the design process of air-to-water heat pumps for the building stockCopyright: EBC
In recent years, sales of heat pumps retrofitting heating energy systems in existing buildings have fallen due to high system costs. Improved system design is considered to increase heat pump systems´ profitability. Assessing the potential, normative design procedures are compared with research findings revealing their shortcomings. It becomes apparent that the sizing of the components as well as the structure of the heating system are crucial factors for efficient operation.
In order to examine different system configurations, simulation results are analysed based on statistical design of experiments. The design configurations are heating energy systems of various sizing. The models represent two typical hydraulic heating system structures, the parallel and serial integration of the buffer storage. The simulations are used to determine the system´s annual final energy consumption. To attain a functional coherence between the components´ sizing and the system´s energy consumption, a nonlinear regression analysis is carried out.
The comparison of the simulation results for the two models proves that interdependencies between the heating system structure and its final energy consumption exist. Apart from that, assessing the relation between the components´ sizing and the final energy consumption reveals nonlinear interdependencies. Furthermore, multiple system designs result in the same energy consumption. In order to limit the solution space for the user, the annuity as second target figure is introduced for relative profitability evaluation of various configurations. Comparing the course of the annuity and the final energy consumption over the change of each component´s size shows that conflicts between the objectives exist, leading to divergent design recommendations.
Based on the findings, the system´s final energy consumption can be reduced by 12 % for serial and by 14 % for parallel integration compared to normative design. Additionally, the economic savings potential is about 3 % for both cases. Therefore, both the component sizing and the heating system´s structure should be integrated in the system design process.
All in all, further assessment of the hydraulic structure´s effects requires the implementation of a detailed building simulation model. Additionally, optimisation is recommended for future work in order to determine ideal design for the user.