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This paper presents an experimental validation procedure of two solar shading calculation techniques - pixel counting (PxC) and polygon clipping (PgC) - and an inter-software comparison to highlight the capabilities and efficiency of each solar shading calculation method. For the first purpose, digital images were taken from the surfaces of small-scale mock-ups specially constructed to generate experimental data for validating simulation results obtained by cases using three different tools: EnergyPlus (PgC based), Shading II SketchUp plug-in (PxC based) and Domus (PxC based). This first task has shown, for prototypes with simple geometries, that all techniques present results in good agreement with the experimental data. However, for a prototype with a hollowed shading device, the PgC-based technique produced results far from the experimental ones since it is not appropriated to simulate multi-hollowed polygons. In order to further explore the capabilities of the two shading calculation techniques, an inter-software comparison has also been carried out for a complex case, considering different building shading solutions, including non-planar trees. The results, in general, have shown that the PxC technique is not limited to geometrical complexities and leads to an accurate and a very fast assessment of sunlit surface fraction. It has also been shown a difference as high as 10 times on the prediction of a daily-integrated solar heat gain by using the two different techniques. [ABSTRACT FROM AUTHOR]

Highlights • Pixel counting technique for interior sunlit area calculation is experimentally validated. • Simulation skillfulness for complex geometries of the pixel counting is investigated. • Pixel counting has good agreement with the experiments. • The impact of internal sun patch position on surface temperature is highlighted. • Importance of computer graphic development to modernize solar energy assessment. Abstract Pixel counting (PxC) emerged as a powerful technique for external solar shading calculations of buildings, providing accurate results with great computational efficiency even for dense geometries. Motivated by this fact and because the technique can be also adapted to cope with interior surfaces without further ado, this paper aims at experimentally evaluating the PxC technique implemented in Domus software for calculating sun patch distribution within building enclosures. For the validation purpose, digital images were taken from the surfaces of an experimental house to compare with the simulation results obtained by using EnergyPlus and two PxC based tools: Domus and Shading II SketchUp plug-in. This first task has shown that the PxC presents results in good agreement with the experimental data, in terms of both location and area of the sun patch. Also, a second case study was constructed to evaluate the capability of PxC for simulating non-convex zones with perforated shading elements. The results, in general, have shown that the PxC can provide accurate results in situations where polygon clipping based algorithms cannot be applied. [ABSTRACT FROM AUTHOR]