The color created by the Egyptians thousands of years ago, has found a modern application. Its pigment can significantly improve the energy efficiency, cooling the roof and walls, as well as collecting sunlight through the Windows.
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The blue color obtained by the Egyptians from the silicate of copper and calcium, often used when creating images of gods and nobles. Previous studies have shown that the absorption of visible light, Egyptian blue emits light in the near infrared range. Today, the team led by researchers from the National laboratory. Lawrence Berkeley confirmed that the fluorescence pigment may be ten times stronger than previously believed. The study described in the journal of Applied Physics.
Measuring the temperature of surfaces covered with Egyptian blue and under the sun, the researchers found that fluorescent blue pigments can emit approximately 100% more photons than they absorb. The energy efficiency of the process reaches 70 percent (infra-red photons carry less energy than visible photons).
This, in turn, helps to understand which colors are most effective for cooling roofs and facades in warm climates. Although the color white is the most traditional and effective for keeping cool in the building due to the reflection of sunlight and reduce energy consumption for air conditioning, owners of buildings often choose other colors for aesthetic reasons. For example, bright white asphalt shingles is almost never used to cover the roofs of houses.
The heating temperature of the Egyptian blue compared to other colors in the sun / © Berkeley Lab
Researchers from the National laboratory. Lawrence Berkeley has already shown that fluorescent red pigments can be an effective substitute for the white color. Now, the choice of the complements of the Egyptian blue. Scientists have also found that fluorescent green and black colors can be produced with yellow and orange accessory pigments.
In addition to the cooling capacity for buildings, fluorescence, Egyptian blue can be useful for solar energy production. When coating Windows of this pigment photovoltaic cells on their edges may convert the energy of fluorescent near-infrared into electricity.