QUANTIFYING REFLECTANCE OF COLOURED MODULES FOR BUILDING APPLICATIONS

Abstract

The dual function of both a façade material and a solar energy generator positions Building Integrated Photovoltaics (BIPV) as a potential solution to the rising concern of environmental impacts in the built environment. However, the aesthetic considerations have been perceived to be a challenge in deploying conventional photovoltaic (PV) modules as part of the building façade. This has led to the use of coloured glass through digital ceramic printing to improve the overall appearance of crystalline silicon (c-Si) PV modules. Yet, glass surfaces are reflective and could affect the visual comfort of individuals (glare). Hence, this study aims to propose a novel methodology to quantify reflectance for coloured PV through the use of directional reflectance method of measurement. In comparison to the more commonly used methods such as integrating spheres and goniometers, the proposed methodology does not require an extensive amount of equipment and could provide better adaptability to various module sizes. The reflected irradiance at various angles would be used to quantify and derive the total reflectance, i.e. specular component via direct measurement; diffuse component by performing bilinear interpolation and numerical integration over the hemisphere. Results have shown that the diffuse component of the coloured PV is isotropic but specular reflectance is still the dominating component. In summary, the results obtained from this study could help to (1) provide an alternative and cost-effective solution to quantify reflectance and (2) facilitate the decision-making of relevant stakeholders from the built industry to adopt coloured PV modules by addressing glare concerns.