University of Twente Student Theses
Investigation of spectro-angular albedo of diffuse, glossy, and specular surfaces for enhanced photovoltaic output
Westerhof, J. (2021) Investigation of spectro-angular albedo of diffuse, glossy, and specular surfaces for enhanced photovoltaic output.
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| Abstract: | The spectral and angular nature of the ground reflectance, i.e., albedo, plays a key role in enhancing bifacial photovoltaic output. A general framework to describe any reflector assumes that the total reflection, while being dependent on the surface roughness, can be expressed as a linear combination of the three types of reflection, i.e, diffuse, glossy, and specular. The surface roughness and its influence on the reflection is modelled using three terms: the Fresnel term, a microfacet distribution and a shadow-masking function. For perfectly diffuse or Lambertian reflection, all light is scattered equally over the hemisphere. For specular reflection, the light is reflected fully over the angle of incidence and for glossy reflection, the light is reflected in a lobe around the angle of incidence. Such an approach using a linear combination of the three types of reflection can enable a more fundamental understanding of the reflector and help in enhancing albedo-dependent photovoltaic yield. Yet important parameters for this computational model are missing. This thesis experimentally provides the necessary parameters using various reflection models. For the measurements, an existing experimental set-up has been optimized and the spectro-angular albedo of a Lambertian surface, paper, photo paper, and aluminium mirror was measured. It is expected that each of these surfaces are extremes of one of the types of reflection: Lambertian and paper are expected to be diffuse, mirror is expected to be specular, and photo paper is expected to be glossy. Diffuse reflection was observed for the Lambertian surface, paper and photo paper and this was modelled with a cosine fit. Glossy behaviour was observed for photo paper as well as slightly for the normal paper and Ward’s reflection model was used to fit glossy/specular reflection onto the paper, photo paper and mirror sample. For the Lambertian reflector it was concluded that all the light was reflected diffusely, and for the mirror, all the light was reflected specularly. The photo paper was an intermediate case where both glossy as well as diffuse reflection was observed, and paper was mostly diffusive but there was also some glossy reflection, especially at larger angles of incidences, due to the Fresnel term. |
| Item Type: | Essay (Bachelor) |
| Faculty: | TNW: Science and Technology |
| Subject: | 33 physics |
| Programme: | Technology and Liberal Arts & Sciences BSc (50427) |
| Link to this item: | https://purl.utwente.nl/essays/86427 |
| Export this item as: | BibTeX EndNote HTML Citation Reference Manager |
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