Solar incidence operators – interface to other methods

Beyond the application of physical optics, the concept of solar incidence operators (SIOP) is an essential component of the novel method presented here. SIOPs allow accurate determination of a scalar target quantity from any given solar incidence profile. Most often, this quantity will be the power transmitted through the target object or absorbed by specific parts of it. However, SIOPs can be generated for any quantities that are induced by solar radiation and can be described by a scalar value (e.g. reflected power, degree of polarisation, luminous exitance, gloss etc.). The formulation of the SIOP relies on spherical harmonics commonly known from quantum mechanics (“orbitals”). In the SIOPs, three-dimensional scattering information gathered in the raytracing process can be stored with a high level of data compression. SIOPs can finally be evaluated in a straightforward way by third-party tools, such as dynamic building simulation, allowing them to perform solar radiation calculations with raytracing accuracy but virtually at no computational costs.

Figure 3 gives an overview of how the developed RadiCal method is applied from a user’s point of view:

• 1. A detailed 3D model of the target to be analysed is imported in a CAD format (e.g. a shaded window or solar collector).
• 2. Physically based material models are assigned to all surfaces of the model.
• 3. The raytracer scanning process is carried out with the desired angular resolution and precision.
• 4. The targeted quantities for all relevant components (e.g. transmission, absorption, reflection) are virtually measured for all sampling directions.
• 5. The sampled data is converted into the functional SIOP form.
• 6. The SIOP data containing the detailed optical scattering information of the target is deployed to third-party simulation tools.