Solar Radiation

Intensity of the sun varies by the clarity of the atmosphere and the angle the sun strikes the surface, called the “incident angle” More perpendicular the suns rays are to the surface, the more heat and light energy Given in units of energy per area (w/m2 or BTU/hr/ft2) Sometimes quoted in energy accumulated per day or year (kWh/m2/day)

Direct/Diffuse radiation Direct radiation, measured perpendicular to the sun’s rays Diffuse radiation, measured horizontal to the surface

Cloudy sky reduces direct radiation and increases diffuse radiation From the total energy of the sun, up to 1/3 can be lost (reflected into space), about 20% reaches as diffuse radiation and the rest is direct radiation

Incident solar radiation values are calculated and visualized within Revit Hourly direct and diffuse radiation data, building geometry and time period of the analysis are taken into account

Absorbed, transmitted, and reflected Incident is the amount of energy striking a surface not how much is absorbed, transmitted or reflected back Material properties affect the above Solar radiaton for a specific time is valuable when finding an initial number for available energy on your site Average incident solar radiation across the entire earth is 240 W/m2

Location and TimeIncident Solar Radiation (BTU/ft2/day) CityMonthHorizontalSouth FaceNorth Face Far from equator Anchorage, AK January July Near equatorMiami, FL January July See more at: