Thousands of years ago, the ancient Egyptians created a blue pigment which they used in their depictions of gods and royalty. Derived from calcium copper silicate, the substance is now known as Egyptian blue – and it could be used to both save power and generate electricity.
Previous research has already shown that surfaces coated with Egyptian blue absorb incoming visible light and emit it as near-infrared light.
In a recent study, though, scientists at Lawrence Berkeley National Laboratory found that the fluorescent effect is 10 times stronger than originally thought. In fact, the pigment emits almost 100 percent as many photons as it absorbs, doing so at an energy efficiency rate of up to 70 percent – infrared photons don't carry as much energy as visible-light photons.
Led by Paul Berdahl, the researchers now hope that the pigment could be used in paint or shingles applied to the roofs of buildings, where it would reflect sunlight and thus keep the inside of the buildings cool, lessening the need for power-hungry air conditioning systems. Bright white paint is already used for this purpose, although it's typically only applied to flat roofs that can't be seen from the ground – blue may well be a preferable color choice for more-visible sloping roofs.
Additionally, if the pigment were used to tint window glass, the emitted near-infrared light could conceivably be absorbed by photovoltaic cells located around the edges of the window, which would convert it into electricity.
A paper on the research was recently published in the Journal of Applied Physics.
Source: Berkeley Lab
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