In order to improve the efficiency of solar collectors, the only effective way is to maintain the maximum acquisition of solar energy while minimizing its convection and radiation heat loss.
The use of high-quality selective absorption coating materials and high transmittance cover material is an important way to meet the above requirements. With the development of solar thermal Utilization technology, the research work of selective absorbing materials in China has a history of more than 20 years. The development process of solar collector is also the development process of coating technology. During this period, from non-selective ordinary black paint to selective lead sulfide, metal oxide coating, from black nickel, black chromium to aluminum-yang polarization coating, such as the replacement process of generation after generation. With the continuous improvement of coating technology, the performance of coating has been greatly improved.
At present, the absorption surface of plate collector in China mainly uses the anodized coloring of aluminum strip and the selective coating of black chromium on the copper strip band. The coating production technology of selective absorption coating of intermittent magnetron sputtering aluminum-nitrogen-aluminum material is developed with the generation of vacuum tube collector, which basically represents the production level of medium and low temperature selective absorption materials in China at present.
Due to the poor weatherability of the coating, it is not suitable for the use of flat-panel collector. At present, the international developed countries, especially in Europe, selective absorption coating production mainly has two characteristics, one is the use of vacuum coating technology, the second is the use of winding continuous coating method. Continuous coating process is used even in wet coating. For example, the Danish Batec company is the production of black chromium absorption coating, in the copper strip using a continuous electroplating method for production. Annual production capacity of a hundred thousand of square meters, the optical properties and weather resistance of the product are very ideal. In addition, several companies in Germany that produce selective coatings, such as Interpane, Tinox and Alanod, are produced by absorbing coatings using vacuum methods and continuous production methods.