Optimal Control of Circuit type Double Skin Façade using Air Conditioning Exhaust in a Cascade Manner

In recent years, there has been increasing number of cases using the double skin façade to satisfy both the indoor views and energy saving. In summer, the double skin façade has a heat shielding effect by exhausting solar heat through natural ventilation and in winter, in addition to the thermal insulation effect by the air layer, a heat collecting effect of solar heat can also be expected. On the other hand, the natural ventilation performance of the double skin façade in summer strongly depends on the outdoor conditions, making it difficult to achieve a stable heat shielding effect. Additionally, high thermal insulation effectiveness is difficult to determine since the air layer is directly influenced by outdoor air temperatures. For this reason, the school facility that is the subject of this study is improving its envelope performance by introducing air conditioning exhaust from classrooms into the circuit-type double skins and using it as a cascade manner. The objective of this paper is to verify the basic performance of this circuit-type double skin façade by unsteady computational fluid dynamics (CFD) analysis, then to propose an optimal control method to improve the effect of reducing the skin load and to clarify its effectiveness by the analysis. In this control, exhaust of air conditioning system cascading into the double skin façade and the direction of airflow (clockwise or counterclockwise) are switched to reduce the skin load by predicting the skin load. 

The following results were obtained:

1. It was confirmed that air temperature in double skin façade was stabilized and heat-load from the surface of buildings was reduced by cascade use compared to a typical double skin façade.
2. Since introduction of the proposed optimal control method makes it possible to select the optimum operation mode, thermal transmission load reduction effect was further improved.