Development of large area sputtered solar absorber coatings

Abstract For effective solar collectors a simple black paint is inadequate. A solution is the use of solar selective coatings, which one of is known as black chromium, deposited electrochemically. The coatings we prepared were produced by reactive dc-magnetron sputtering. The coating consists of a graded mixture of chromium oxide and chromium nitride. Experimental design procedures (face centered cubic plans) were applied for the optimization of the production parameters. The maximum sample size was 0.6 m × 1.1 m in the lab and 2 m × 3 m in a following pilot production plant. The coating is deposited directly on copper sheets without the commonly used anti-corrosion nickel coating in between, on a metallic infrared reflecting coating on float glass or high temperature stable polymers. The durability of the absorbers was found to be sufficient for the application in ventilated flat plate collectors containing moisture according to the tests and requirements proposed by the Solar Heating and Cooling Program of the International Energy Agency.