1.2. Research question and objective
1. How can the accuracy of modelling solar-induced energy flows in building science be enhanced?
- 1.1. Which optical processes, beyond simple geometrical optics, are relevant, and how can they be considered? (e.g. thin-film interference, polarisation, surface roughness)
- 1.2. Is it possible to create a physical-optics-based raytracer that can be used to efficiently evaluate the solar properties of relevant building components, in particular combinations of glazings and shading devices?
- 1.3. Can the raytracer be designed in a way that allows a seamless transition or downgrading to existing models?
- 1.4. If and how can the highly accurate raytracing be deployed to practical application in dynamic building performance simulation?
In order to answer these questions, the work was subdivided into subtasks. The subtasks are addressed by following these primary objectives:
Objective 1: state of the art analysis
In order to understand how researchers and practitioners currently perform the modelling of solarrelated energy flows in building science, the current research and the international standards in force are reviewed. The impact and root causes of the limitations associated with the current models and workflows are analysed. Further, the relevance of optical processes and advanced physical optics models are analysed, and their adaption for use in building science is evaluated.
Objective 2: development of a physical-optics-based raytracer
Based on the knowledge and requirements gained in the first task, a suitable novel raytracing method is designed and implemented. The method shall be able to consider practically relevant effects of physical optics and cover the entire global radiation spectrum. Furthermore, the raytracer shall be implemented in an open design approach based on object-oriented programming methods in order to facilitate the seamless addition of new scattering and material models in the future. Further, the raytracer shall optionally be able to apply existing simple models in order to establish a consistent transition to current modelling approaches.
Objective 3: development of a method to provide raytracing results for building performance simulation
A method to deploy the information contained in the accurate and detailed results of the raytracing analysis shall be established. The method should allow thermal simulation methods, particularly dynamic building performance simulation tools, to exploit the raytracing results. While the determination of the scattering (i.e. absorption and transmission) characteristic of the analysed target object requires an elaborate and potentially multi-hour-long raytracing process, its results shall be provided in a form that allows a fast and accurate evaluation. This is crucial for dynamic simulation, as subhourly evaluation steps for multi-month-long periods are required in building performance simulation, resulting in a large number of necessary evaluations.
Objective 4: proof of concept and validation
Due to its complexity and novelty, the developed method’s validity and feasibility, as well as its correct implementation, must be demonstrated transparently and comprehensively. For this purpose, several validation examples and application cases shall be performed. These validation steps shall be performed at different levels: physical optics modelling, application for building simulation and a full-scale empirical validation of the developed workflow.