Design of Roofs for Increased Solar Potential BIPV/T Systems and their Applications to Housing Units

This paper presents a design methodology of housing units' roofs for increased solar potential, and the application of some of these designs to energy efficient housing units. The basic principle is the utilization of complete near-south facing roof surfaces for solar collectors that generate both heat and electricity. The design of roof surface morphology incorporates the application of building-integrated photovoltaic/thermal (BIPV/T) system that generates simultaneously electrical and thermal energy. The methodology employs a correlation between thermal and electrical output of the BIPV/T system, and analysis of the effect of combinations of tilt and orientation angles of the BIPV/T system. Optimal configurations are implemented in the roof of a rectangular housing unit. Gable roof with 45 tilt angle is used as reference. The basic rectangular shape is redesigned to follow the contour of optimal roof geometries. Energy performance, in terms of heating and cooling demands, is analyzed to evaluate the effect of roof shape. Some roof shape designs enable increasing the potential of BIPV/T systems by up to 30%, as compared to the reference roof. The effect of roof design on heating and cooling loads is not highly significant (<5%). While redesigning unit shapes does not significantly affect their energy performance, it can provide some design flexibility. In addition to optimizing energy production, the integration of photovoltaic/thermal systems in surfaces with different orientations enables a spread of the timing of peak electricity generation over up to 3 hours. This feature can be beneficial in reducing mismatch between demand and supply of the grid.