An optimal implementation strategy of the multi-function window considering the nonlinearity of its technical-environmental-economic performance by window ventilation system size

To address the problems of the indoor air quality deterioration and energy consumption, this study proposed the multi-function window combined with a ventilation system and solar photovoltaic blind. In this study, multi-objective optimization for determining the optimal design of the multi-function window was conducted along with nonlinearity analysis. The main findings can be summarized as follows. First, from the technical-environmental performance's perspective, the amount of solar radiation and wind volume entering the room were found to be key factors causing nonlinearity. In particular, the total energy consumption and indoor CO₂ concentration decreased whereas the predicted percentage dissatisfied deteriorated with the increasing the size of the window ventilation system. Second, from the economic performance's perspective, the absolute and relative investment values showed nonlinear relationships with the amount of electricity generated and the total energy consumption. Especially, as the window ventilation system size increased, the absolute investment value decreased due to the reduced amount of electricity generated, and the relative investment value decreased except when the energy supply was larger than the energy demand. Finally, the window ventilation system size was most suitable when it was 3–5% of the multi-function window's size according to the orientation, from a holistic view of the technical-environmental-economic performance.