The page combines glazing optical properties, direct and diffuse radiation models, annual solar indicators, and transmitted solar radiation through a horizontal film sheet.
Matlab sources are preserved in matlab-source/cuc04. The browser version keeps the original equations and presents them with interactive inputs and charts.
CUC04
Optical properties of glazing
Based on incident angle, refractive index, extinction coefficient, and glazing thickness.
CUC04a
Direct and diffuse solar radiation
Recreates the altitude-response curves for several atmospheric transmittance values.
PP1, PP2, and PP3 are three atmospheric transmittance cases used to compare how clearer or hazier skies change direct and diffuse radiation.
CUC04b
Annual solar indicators
Equation of time, solar declination, and extraterrestrial radiation throughout the year.
CUC05
Sun position and transmitted radiation
Combines solar geometry, radiation, and glazing transmission through a 24-hour cycle.
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Time (hr)
Solar altitude
Solar azimuth
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Time (hr)
Direct outdoor
Diffuse outdoor
Direct under glazing
Diffuse under glazing
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Time (hr)
Transmissivity
Reflectivity
Absorptivity
CUC05
Sun position and transmitted radiation
Combines solar geometry, radiation, and glazing transmission through a 24-hour cycle.
Time (hr)
Solar altitude
Solar azimuth
Time (hr)
Direct outdoor
Diffuse outdoor
Direct under glazing
Diffuse under glazing
Time (hr)
Transmissivity
Reflectivity
Absorptivity
Optical Equations
Fresnel and absorption terms
RFcal computes reflected fractions from incident angle and refractive index.
AB = exp(-FK * FL / cos(θ′)) controls attenuation through the glazing.
CUC04 and CUC05 both use transmissivity, reflectivity, and absorptivity relations based on repeated internal reflection.
Solar Equations
Radiation and geometry
RAD = J0 * sin(α) * PP1/sin(α) is used for direct solar radiation, where α is the solar altitude angle and PP is atmospheric transmittance.
RADS follows the diffuse-radiation expression from RADcal.m.
CUC05 uses Tokyo latitude, longitude, and Julian day as defaults, and can be adapted to other locations by changing latitude, longitude, and day of year.
Solar declination reference: DEC = 23.45 * sin(2π * (284 + Julian day) / 365).
Equation-of-time reference: EQT(min) = 9.87 * sin(2B) - 7.53 * cos(B) - 1.5 * sin(B), where B = 2π * (Julian day - 81) / 364.
Standard longitude reference: LGTstd = LGT - (LGT mod 15).
SALT = asin(sin LAT * sin DEC + cos LAT * cos DEC * cos HAG) defines solar altitude, where LAT is latitude, DEC is solar declination, HAG is hour angle, and SALT is solar altitude. SAZM = acos((sin SALT * sin LAT - sin DEC) / (cos SALT * cos LAT)) defines solar azimuth, where SAZM is solar azimuth.