Daylight Illuminance and Solar Irradiance on Obstructed Vertical Fenestrations

Daylight illuminance and solar irradiance on vertical fenestrations are important to the energy saving designs of artificial lighting and estimation of power generation from vertical building integrated photovoltaic (BIPV) systems. The surrounding buildings in the densely built urban environment, however, may greatly reduce the daylight from the sun and sky while the reflected components may be increased. The paper proposes an approach to determine the vertical daylight illuminance and solar irradiance in an infinitely long city canyon. The 15 CIE Standard Skies are employed to represent the sky radiance and luminance conditions. Results obtained by the proposed approach were compared against those simulated using RADIANCE program at solar noon of June 23 under various CIE Skies. The year-round vertical illuminance and irradiance in 2004 were calculated and the daylight glare index of rooms with specified fenestration systems was estimated. The results and implications are discussed.