Direction Dependence of Savings on Cooling and Heating Loads by Energy Efficient Windows

Abstract

Abstract:The energy saving performance of energy efficient windows has strong dependence on window direction. Transmitted insolation level definitely affected the cooling and heating load. Simple simulation on the decrement of cooling load and the increment of heating load of a shading window compared with those of a transparent window show the prospect of energy saving effect clearly. From southeastward to southwestward, shading window even enlarges total heating and cooling loads when the thermal transmission is the same. However, if the shading coefficient of window is switched between summer and winter, total cooling and heating load can be reduced. This result clarifies the importance of "smart window".

Improving the optical properties of switchable mirrors based on Mg–Y alloy using antireflection coatings

“…When using highshading solar control windows southerly, the increase in heating load in the winter is larger than the decrease in cooling load in the summer. Therefore, switchable optical properties, such as high transmittance of $ 70% in the transparent state and a large dynamic range between the reflective and transparent states are necessary for window applications to reduce the total load of cooling and heating [6]. Furthermore, by applying switchable mirrors with the above properties to windshields of cars, it would be possible to suppress discomfort of hot air after parking in the summer using the reflective state, and also possible to reduce consumption of fuel due to air-conditioning.…”

“…For the calculation we assumed the following conditions: (1) For the AR layer, the refractive index n was constant and the extinction coefficient κ was zero in the visible range; (2) the thicknesses of the Mg 0.4 Y 0.6 H x , Ta, and PdH 1 À δ layers were 50, 2, and 3 nm, respectively; (3) the complex optical indices of Mg 0.4 Y 0.6 H x and PdH 1 À δ layers were the evaluated values from the previous study[5] and those of Ta were the reference values[6]; (4) the refractive index n and the thickness of the substrate were 1.5 and 1 mm. The layer structure to calculate T vis values of AR coated switchable mirrors in the transparent state.…”