Description
New selective coatings and collector developments in Macedonia
Center for plasma technologies PLASMA LTD
Challenge
To produce solar thermal flat plate or vacuum tubes collectors with high level of coefficient of efficiency,
beside iron-free antireflective glass and good isolation, it is also necessary:
-Very good selective coating where solar radiation will be conversed into heat with maximum absorption,
minimum reflection and minimum heat emission
-High level of heat transmission from selective coating to the medium and
-Increasing absorber area very close to aperture and gross area of the collector as much as possible
Solution
Selective coating:
-Maximum absorption, minimum reflection and minimum IR emission
-Very good stability in temperature higher than 200 °C , 300 °C, 400 °C and more according the application
Heat transmission:
-It is very important the absorber to has very good or maximum heat transmission from selective coating to
the medium which circulate inside of absorber
-For this purpose, PLASMA researched, developed and constructed absorbers where coefficient of heat
transmission is higher than existing
Increasing absorber area very close to the aperture area of the collector
-Almost in all solar thermal collectors, absorbers are soldered with collecting tubes and painted with black
organic paint after soldering
-It means – around 7-8% smaller selective coated absorber surface with: smaller absorption and higher IR
heat emission or higher heat loses compare with selective absorber surface
-Plasma produce collecting tubes with ultrasonically welded selective coated wings and increased absorber
area very close practically the same with aperture area