In this paper, hourly terrestrial radiation: direct beam, diffuse and global solar radiation are modelled and calculated based on daily measured data for a horizontal surface. In addition, the same parameters were modelled for inclined surfaces. Most of the parameters modelled in this work represent a part of the input data required by building thermal simulation and solar energy systems software. Important trends of the solar radiation on tilted surfaces as a function of time and direction are

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... being presented and discussed. The comparison of some of the results with measured data from other sources shows good agreement. The effect of tilt angle and orientation on the incident solar radiation fluxes arepresented along with optimum surface tilt angles and directions for maximum solar radiation collection in Muscat area. The results presented in this paper are quite useful for quick estimation of solar radiation for calculations of cooling load and solar collector performance. Also, the models and the computer code developed in this work form the backbone of any computer-aided building thermal design and solar systems design calculations.