Science

Ancient Egyptian pigment may find use on power-saving roofs

Ancient Egyptian pigment may f...
Egyptian blue is considered to be the world's first synthetic pigment
Egyptian blue is considered to be the world's first synthetic pigment
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Egyptian blue is considered to be the world's first synthetic pigment
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Egyptian blue is considered to be the world's first synthetic pigment

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

5 comments
jerryd
Or used to make PV more efficient by converting the full light to ones colors PV uses best, most efficiently.
MartinVoelker
Thermoplastic Polyolefin or TPO is the most commonly used roof membrane on commercial buildings like warehouses because of its easy installation and superior lifespan. If TPO, which is typically white, could be infused with that pigment the added cost might be offset by lower cooling needs, or work in tandem with bi-facial PV which is coming into full scale production now.
Easy
I had the pleasure during the '90s, of living on a few acres of Pacific beach in Costa Rica. The property I'd bought was invaded by 'squatters', who were evicted by the Federal police eventually, but left it bare and unguarded against another attempt. I had to live on the property for over a year, think cross between "Castaway" and Gilligan's Island. In the course of things I built a modest structure to live in, with full bath and septic system-tile field and of course a water well which I dug with a shovel. All that to say that hot water for my morning shower heated up fastest in the green bucket, not the white or the blue, meaning green absorbs a lot of energy. Blue was the slowest, maybe because of the explanation above, that it re-radiates the high frequency (blue, ultra violet) light
Don Duncan
Other than a mirror I didn't know any color was more reflecting than a ceramic white. If infusing this dye is better I would like to use it on my roof to mitigate 100+ days of 100+ temps. Too bad all the infrared can't be harnessed to produce electricity.
Jinpa
Blue glass is a bad idea, because it causes or promotes depression. Brown or green glass doesn't.