A dual-mode internal window management device for energy conservation

The design of a simple energy conserving window management system is described, and its heat transfer characteristics are calculated. The device serves as a quasi-active solar collector during winter daytime, provides added insulation comparable with that of vented storm windows during winter nighttime, and rejects solar heat during summer cooling periods. The problem of avoiding the intensity of direct sun through windows while obtaining essentially all the associated heat is effectively solved with a window system of this type. The results of the numerical modeling show that the dual shade:will be approximately 90% as energy efficient as an unshaded window while intercepting direct sunlight;will save about 40% on energy losses through a single pane window during winter nighttime;will reduce solar heat gain by about 70% during peak-power summer air conditioning periods.