Modern application of ancient Egyptian pigment to improve energy efficiency
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.
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 Lawrence Berkeley National Laboratory confirmed that the fluorescence pigment may be ten times stronger than previously believed.
Measuring the temperature of surfaces coated in Egyptian blue and related compounds while they are exposed to sunlight, Berkeley Lab researchers found the fluorescent blues can emit nearly 100 percent as many photons as they absorb. The energy efficiency of the emission process is up to 70 percent (the infrared photons carry less energy than visible photons).
The finding adds to insights about which colors are most effective for cooling rooftops and facades in sunny climates. Of corse, white, as in Ashgabat, which is co-called white-marble city, is the most conventional and effective choice for keeping a building cool by reflecting sunlight and reducing energy use for air conditioning.
Berkeley Lab researchers have already shown that fluorescent ruby red pigments can be an effective alternative to white; this insight on Egyptian blue adds to the menu of cooling color choices. In addition to its cooling potential for buildings, Egyptian blue's fluorescence could also be useful in producing solar energy.
Used on windows tinted with the blue, photovoltaic cells on the edges can convert the fluoresced near-infrared energy to electricity.
Substantial research over the years from Berkeley Lab’s Group has found that reflective roofs and walls can cool buildings and cars. This reduces the need for air conditioning and mitigates the urban heat island effect.
By reflecting the sun’s rays back to space, these cool materials also release less heat into the atmosphere, thus cooling the planet and offsetting the warming effects of substantial amounts of greenhouse gas emissions.
