Abstract
With the increasing adoption of building integrated photovoltaics (BIPV), concerns arise about potential glare. While recommended criteria to assess glare exist, it is challenging to apply these in the spatial and temporal domains and communicate the complex data to planning authorities and clients. This paper presents a new computational workflow using annual daylight simulation, material modelling using bi-directional scattering distribution functions (BSDFs) and image-based postprocessing to obtain 3-dimensional renderings of cumulative annual irradiance and glare duration on the built environment. The annual daylight simulation considers relevant sun positions in high temporal resolution (15-min timesteps) and measured BSDFs to model different PV materials. The postprocessing includes a relative irradiance visualisation comparing the impact of a proposed PV proportional to a reference material. It also includes a new spatio-temporal workflow to assess the glare duration based on recommended thresholds. This workflow is demonstrated with a case study of a proposed PV roof for a church, assessing the glare potential of two different PV materials. The visualisations indicate glare durations well below the thresholds with satinated PVs, and in noncritical zones outside observer positions with standard PVs. Thus the proposed PV roof does not cause any disturbing glare.
Highlights
The integration of photovoltaics (PV) into building façades as building integrated photovoltaics (BIPV) holds opportunities in meeting the increasing demand for renewable energy
PV proportional to a reference material. It includes a new spatio-temporal workflow to assess the glare duration based on recommended thresholds
This workflow is demonstrated with a case study of a proposed PV roof for a church, assessing the glare potential of two different PV materials
Summary
The integration of photovoltaics (PV) into building façades as building integrated photovoltaics (BIPV) holds opportunities in meeting the increasing demand for renewable energy. The appearance of BIPV corresponds to that of glass façades, as PV modules are typically laminated with glass. This has in turn influenced the development of urban architecture, with a shift from traditional construction materials such as plaster or fibre cement towards an increasing prevalence of glass façades in general, and BIPV in particular. A negative side effect of this development are potentially disturbing reflections from specular façades, which pose a challenge for building and environmental authorities [1]. The acceptance of BIPV by architects, authorities and communities requires a high degree of flexibility in design, and a form of governance that limits specular reflections from façades. The RPG is implemented for PV installations according to Article 32a of the federal spatial planning ordinance (Raumplanungsverordnung, RPV [11]), which states that roof-mounted PV should (a) appear as homogeneous surface, (b) be of low reflectance in accordance with the state of the art, and (c) not overhang the roof edges
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