Solar filters based on iron oxides used as efficient windows for energy savings

The application of windows coated with solar filters is intended to improve the interior comfort of buildings by blocking the transmittance of heat while allowing visible light to pass through. In this report we test the physical properties and thermal behavior of solar filters based on iron oxides. These filters consisted of a thin film of FeO and Fe2O3. This film was deposited on soda-lime glass substrates of 600 · 300 mm by rf magnetron sputtering using a high-purity Fe target (99.99%) in an argon plasma. Since the sputtering conditions and the dimensions of the equipment used facilitated the oxidation of iron, we subjected small samples of 45 · 22 mm to a heating reduction treatment in a hydrogen and nitrogen atmosphere for 10 min at 400 C. This treatment allowed us to obtain the desired oxidation state of iron within these thin films. The solar filters had a transmittance of 30.2% for the visible light spectrum and 39.9% for the nearinfrared spectrum. Furthermore, the reflectance of these filters was determined to be 17.5% and 19% for visible and near-infrared light, respectively. A simulation of thermal behavior in houses at different locations in Me´xico was performed using Energy-10 software. These data were used to determine energy savings attributed to the use of when iron-based solar filters are used on windows. These solar filters resulted in a 9–16% reduction in the amount of energy required for air conditioning (heating and cooling). In addition, a simulation was made at Mexicali BC using the commercial glass Reflectasol AP Tintex of Vitro Co., which concluded that the FeO-based solar filters performed better than the other tested. 2006 Elsevier Ltd. All rights reserved