Novel sol-gel based selective coatings: From coil absorber coating to high power coating

摘要

Single layer black selective coatings for solar thermal energy conversion were produced by low cost sol-gel dip-coating, spin-coating and coil-coating methods, the last made on the industrial line of the Alanod company (DE). For the deposition, pigment dispersion was prepared by milling a mixture of a black spinet (FeMnO4) pigment, whose surface was modified with trisilanol heptaisobutyl PUSS dispersant, dried and re-milled with (3-glycidoxypropyl)trimethoxysilane (GLYMO) and Ti(i-OPr)(4) acting as binders. The corresponding organic-inorganic hybrid consisted of silica clusters linked together with poly(ethyleneoxide) chains acting as a network former. The as-prepared nanocomposite dispersion served for the deposition of coil absorber coatings (similar to 800 m) on aluminium coil in an industrial plant in the Alanod factory. They gave solar absorptance of 0.905 and thermal emittance of 0.12 and excellent homogeneity. The stability of the coatings at 400 degrees C was excellent but corrosion resistance was moderate (5 days in salt spray).