Energy Efficiency Optimization of Different Curved Building Integrated Photovoltaic (BIPV) Façades by a Parametric Shape Design Method: A Cross-Region Study

With the development of green building technologies and photovoltaic materials, the emergence of flexible BIPV products has enriched building aesthetics and can also optimize the energy performance of building envelopes. However, it has yet to be adequately addressed how to maximize the energy potential of curved BIPV façades. Therefore, this paper investigates the energy efficiency of curved BIPV façade by building envelope form optimization. There are 22 types of curved BIPV façade investigated with design parameters including 3 intervals, 5 curvature and 2 combination methods, which is conceived to explore their production capacity in two cities, Beijing, China and Kuala Lumpur, Malaysia. The results prove that (1) There are differences in the annual power generation per unit of PV area for different forms of curved BIPV façade: The annual energy production ranged from 79.13 kW·h/m2 to 110.68 kW·h/m2 in Beijing, while the annual energy production ranged from 52.49 kW·h/m2 to 71.25 kW·h/m2 in Kuala Lumpur. (2) Due to latitude and longitude, the optimized curved BIPV façade in Kuala Lumpur can improve energy efficiency by 4.49% compared to flat BIPV façades, corresponding to a 3.06 kW·h/m2 increase in annual PV system production capacity per unit of PV area. However, in Beijing, the curved BIPV façade has no increased production capacity compared to flat BIPV façades. (3) Different design parameters optimize the energy performance of the curved BIPV facade to different degrees. Firstly, the increased interval of BIPV units can improve energy efficiency by up to 18.55% (Beijing) and 28.12% (Kuala Lumpur) for the convex curved BIPV façade annually, but not significantly for the concave. Secondly, the reduced angle can improve energy efficiency by up to 37.50% (Beijing) and 28.68% (Kuala Lumpur) for the concave BIPV façade, and 11.99% growth for the convex façade in Beijing annually but insignificant in Kuala Lumpur. Thirdly, with the combination of convex and concave BIPV units, it is possible to improve energy efficiency by up to 10.21% (Beijing) and 14.56% (Kuala Lumpur) annually. Thus, it is a feasible method to optimize curved BIPV façade’s energy performance by parametric form design in early stage. In addition, it is proof that the spatial and temporal distribution characteristics of solar energy in different regions cannot be ignored, which determines whether curved BIPV technology can optimize the production capacity efficiency of building façade systems. The methodology and data presented in this paper can provide guidance in both energy performance optimization and equipment selection by assessing benefits of curved BIPV façade application in different regions.