Estimation of obstructed vertical solar irradiation under the 15 CIE Standard Skies

The estimation of solar heat gain via vertical fenestration is important in energy-efficient building design and operation especially for subtropical Hong Kong. Being one of the most populated cities in the world, buildings in Hong Kong tend to be densely constructed. In this regard, the shading effect of surrounding buildings could significantly limit solar radiation from the sun and sky to the window while certain amount of solar radiation would be reflected from the opposite façades. This paper presents a calculation approach to compute solar radiation on obstructed fenestration for both overcast and non-overcast skies. Performance of the proposed method is evaluated by comparing with simulated results of a sophisticated lighting program and field measurements. The findings are essential for the assessment of both active and passive building energy saving techniques including shading and building integrated photovoltaic systems in metropolitan environment. •An approach to determine irradiance on fenestration under obstruction is proposed.•The anisotropic CIE Standard Skies are employed to model sky radiance.•Simple equations are given to determine sky irradiance under different obstructions.•The approach is effective and comparable with comprehensive simulations.