First, the development of the simulation-based multi-objective computational platform to evaluate and optimize passive phase change materials (PCMs) in buildings was performed. For this, the accuracy of different PCM models to represent their thermal performance in buildings was evaluated, including specific phenomena such as phase change hysteresis. Furthermore, a proper numerical setup of algorithms was tested to achieve accurate results using whole-building performance simulations in the EnergyPlus software. A parametric module was developed to dynamically modify the thermophysical properties of various PCMs simultaneously. Then, the core of the platform was achieved by coupling this module with EnergyPlus and a multi-objective genetic algorithm.
Using the newly developed numerical tools, several applications were performed to validate and improve the platform workflow, to determine innovative building applications of PCMs, to understand their behavior in buildings, and to derive general design rules throughout different climate regions.
Regarding the applications, the performance of PCMs in buildings was evaluated and optimized for different incorporation technologies (e.g. microencapsulated PCMs) and in combination with other passive strategies (e.g. embedded in insulating cementitious foams). Moreover, innovative utilization of PCMs with different melting temperatures was proposed, while their optimization was performed for various climate-representative locations within WMO Region VI (Europe). Beyond the specific results reported from these applications, the performance of PCMs in buildings showed itself to be complex, and their proper design essentially requires the use of whole-building performance simulation. The melting temperature, amount, and location of PCMs should be carefully designed to maximize their thermal performance. The proposed approach of using PCMs with different melting temperatures was preferred. This approach achieved the best performances in various climate zones and case studies with both heating and cooling thermal loads.
Because a moderated performance of passive PCMs was mostly observed (compared to their theoretical potential), novel effectiveness indicators were developed to deeply understand the behavior of PCMs in buildings. By employing these novel indicators, unprecedented findings were obtained, which revealed that building design variables, such as the window-to-wall ratio, have a significantly higher impact on the effectiveness of PCMs than typically employed PCM design variables, such as melting temperatures. These unprecedented findings indicate that designers could significantly improve the performance of passive PCM systems in buildings by simultaneously designing the PCMs along with other building design variables, preferably at the initial stage. Moreover, the results show that a contradiction can exist between the building’s energy performance and the effectiveness of PCMs. This means that the best effectiveness for PCMs is achieved in buildings with a low energy performance.
Apart from the research activities, the fellow performed other activities to carry out his research career plan, including the preparation and application for new research funding.
To encourage the dissemination of the obtained results and their exploitation, several actions were performed within the project, among them:
- Publication of two research papers in peer-reviewed journals. One more is under review.
- Publication and presentation at three international conferences.
- Open-access publication of research data (five datasets) of the project at the Zenodo repository (
https://zenodo.org/communities/0e-buildings/(öffnet in neuem Fenster)).
- Plenary presentation at the IBPSA LATAM 2023 conference.
- Website of the project.
- Invited speaker at the Postdoc Career Weeks 2022 of the Rhine-Main University Alliance.
