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The power consumption of buildings is exacerbated in modern societies. The most effective load in buildings is heating and cooling systems. Numerous studies have been done on energy saving for buildings recently. Windows are one of the most thermal loads that cause the loss of heat from inside to outside a room during winter. This paper demonstrates an alternative insight into the use of double glazed windows in average climate environments. The proposed system uses an air inject system to impact the heat transfer properties of the window considering the trade-off between the heating load energy saving and air injection power consumption. The theoretical analysis showed a reduction of 52 % in the thermal loss of the window, in addition to a declination in the heat transfer coefficient of the window from 3.5 to 1.8 W/m2K. Consequently, an energy saving of 19 % in the heating capacity has been achieved.

The accumulation of soiling on photovoltaic (PV) modules affects PV systems worldwide. Soiling consists of mineral dust, soot particles, aerosols, pollen, fungi and/or other contaminants that deposit on the surface of PV modules. Soiling absorbs, scatters, and reflects a fraction of the incoming sunlight, reducing the intensity that reaches the active part of the solar cell. Here, we report on the comparison of naturally accumulated soiling on coupons of PV glass soiled at seven locations worldwide. The spectral hemispherical transmittance was measured. It was found that natural soiling disproportionately impacts the blue and ultraviolet (UV) portions of the spectrum compared to the visible and infrared (IR). Also, the general shape of the transmittance spectra was similar at all the studied sites and could adequately be described by a modified form of the Ångström turbidity equation. In addition, the distribution of particles sizes was found to follow the IEST-STD-CC 1246E cleanliness standard. The fractional coverage of the glass surface by particles could be determined directly or indirectly and, as expected, has a linear correlation with the transmittance. It thus becomes feasible to estimate the optical consequences of the soiling of PV modules from the particle size distribution and the cleanliness value.