An­cient Egyp­tian pig­ment can boost en­ergy ef­fi­ciency

Millennium Post - - Mp World -

WASH­ING­TON DC: A colour de­vel­oped by Egyp­tians thou­sands of years ago can boost en­ergy ef­fi­ciency by cool­ing rooftops and walls, and could also en­able so­lar gen­er­a­tion of elec­tric­ity via win­dows, sci­en­tists say.

Egyp­tian blue, de­rived from cal­cium cop­per sil­i­cate, was rou­tinely used on an­cient de­pic­tions of gods and roy­alty, ac­cord­ing to the study pub­lished in the Jour­nal of Ap­plied Physics.

Pre­vi­ous stud­ies have shown that when Egyp­tian blue ab­sorbs vis­i­ble light, it then emits light in the near­in­frared range.

Now, a team led by re­searchers at the Lawrence Berke­ley Na­tional Lab­o­ra­tory (Berke­ley Lab) in the US has con­firmed the pig­ment's flu­o­res­cence can be 10 times stronger than pre­vi­ously thought.

Mea­sur­ing the tem­per­a­ture of sur­faces coated in Egyp­tian blue and re­lated com­pounds while they are ex­posed to sun­light, re­searchers found the flu­o­res­cent blues can emit nearly 100 per cent as many pho­tons as they ab­sorb.

The en­ergy ef­fi­ciency of the emis­sion process is up to 70 per cent (the in­frared pho­tons carry less en­ergy than vis­i­ble pho­tons).

The find­ing adds to in­sights about which colours are most ef­fec­tive for cool­ing rooftops and fa­cades in sunny cli­mates.

Though white is the most con­ven­tional and ef­fec­tive choice for keep­ing a build­ing cool by re­flect­ing sun- light and re­duc­ing en­ergy use for air con­di­tion­ing, build­ing own­ers of­ten re­quire non­white colours for aes­thetic rea­sons.

For ex­am­ple, bright-white as­phalt shin­gles are al­most never used on slop­ing res­i­den­tial roofs.

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 colour choices.

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