Modelling and simulation of intelligent facades

Abstracts from the two papers made during the project

Abstract #1

Thermal radiation within buildings is a significant component of thermal comfort. Typically, the methods applied for calculating view factors between a person and its building surfaces requires great computational time. This research developed a view factor calculation method suitable for building energy simulations. The method calculates view factors by numerical integration of projected area factor. Overtime the projected area factor of a person has been simplified by geometrical shapes. These shapes were compared with more complex equations on precision and calculation time. The same was done for the resulting view factors, where the results were compared with view factors found by ray tracing. While geometrical simplifications of the human body gave the fastest calculations, the complex equations gave the most accurate results. Non-rectangular surfaces and obstacles were treated by comparing intersection points with the edges of the surface, making the method applicable to rooms with complex geometry. The method for calculating view factors is robust and applicable to building energy simulation tools. Calculation time can be long depending on the complexity of geometry, grid-size and the choice of method for the projected area factor, but view factor calculations are done only once for a whole year simulation.Thermal radiation within buildings is a significant component of thermal comfort. Typically, the methods applied for calculating view factors between a person and its building surfaces requires great computational time. This research developed a view factor calculation method suitable for building energy simulations. The method calculates view factors by numerical integration of projected area factor. Overtime the projected area factor of a person has been simplified by geometrical shapes. These shapes were compared with more complex equations on precision and calculation time. The same was done for the resulting view factors, where the results were compared with view factors found by ray tracing. While geometrical simplifications of the human body gave the fastest calculations, the complex equations gave the most accurate results. Non-rectangular surfaces and obstacles were treated by comparing intersection points with the edges of the surface, making the method applicable to rooms with complex geometry. The method for calculating view factors is robust and applicable to building energy simulation tools. Calculation time can be long depending on the complexity of geometry, grid-size and the choice of method for the projected area factor, but view factor calculations are done only once for a whole year simulation.

Abstract #2

The research aims to develop a simplified calculation method for double glazing facade to calculate its thermal and solar properties (U and g value) together with comfort performance (internal surface temperature of the glazing). Double glazing is defined as 1D model with nodes representing different layers of material. Several models with different numbers of nodes or in various positions are compared and verified to find a simplified method which can calculate the performance as accurately as possible. The performance calculated in terms of internal surface temperature is verified with experimental data collected in a full-scale facade element test facility at Aalborg University (DK). Comparison was con-ducted between the simplified method and WIS software on the accuracy of calculating internal surface temperature of double glazing facade. The method is based on standards EN410 and EN673, taking the thermal mass of the glazing into account. In addition, angle and spectral dependency of solar characteristic is also considered during the calculation. By using the method, it is possible to calculate entire year performance at different timesteps, which makes it a time economical and accurate tool in design stage of double glazing facade.