Abstract
The possibility of obtaining thermal energy from the sun for household bathing and washing has resulted to growth in market for solar thermal applications with new types of solar absorbers currently being investigated either to compliment or to replace existing ones. This study focuses on CuFeMnO4 absorber paint by addressing aspects which have little attention regarding improvement of optical absorption for higher efficiency such as texturing the metal substrates on which to coat CuFeMnO4 absorber paint. In this study, texturing was done controllably in order to match the incoming solar radiation wavelength and the surface topography and morphology. Textured and untextured aluminum sheets coated with titanium dioxide (TiO2)-bound CuFeMnO4 absorber paint were used to fabricate prototype flat plate solar thermal collectors. Titanium dioxide (TiO2) was chosen here as binder to a spectrally selective CuFeMnO4 absorber paint. The TiO2-bound CuFeMnO4 absorber paint was applied by a simple, cheap and up-scalable dip coating method over the aluminum sheets. The aluminum sheets were electro-chemically textured to enhance optical absorption and photo-thermal conversion efficiency for both the textured and untextured prototypes were compared. The efficiency characterization of the prototype collectors was done by measuring the global solar irradiance, fluid inlet, fluid outlet and ambient temperature. Both instantaneous and steady-state efficiencies were determined mathematically, and it was found that the prototype collector whose absorber plates were textured recorded higher instantaneous and steady-state efficiencies compared to the collector fabricated from untextured aluminum plates.
Highlights
Increase in human population accompanied by the energydriven lifestyle has led to the search for more energy sources to complement the existing and established sources to sustain the high energy demands
Paint-based solar absorber offers the opportunity to produce at large scale solar thermal collectors at a cheaper cost and simpler technology as opposed to the conventional electro-chemical, chemical and physical vapor deposited (PVD) coatings whose products were expensive and discouraging the use of solar energy as a renewable source
The straightline graphs are the best line of fit of the data points for both textured and untextured surface exposed to different levels of irradiation (300W/m2, 700W/m2 850W/m2)
Summary
Increase in human population accompanied by the energydriven lifestyle has led to the search for more energy sources to complement the existing and established sources to sustain the high energy demands. Paint-based solar absorber has become cheap alternative to the more sophisticated surface treatment techniques such as electro-chemical, chemical and physical vapor deposited (PVD) coatings. Paint-based solar absorber offers the opportunity to produce at large scale solar thermal collectors at a cheaper cost and simpler technology as opposed to the conventional electro-chemical, chemical and physical vapor deposited (PVD) coatings whose products were expensive and discouraging the use of solar energy as a renewable source. It is until recently that a study by [10] of versatile roll-to-roll (R2R) process based on the anodization of aluminum foils for the controlled nano-texturing that the aspect of surface roughness was highlighted This technique could treat substrates over large area with tunable surface topography. The improvement of absorbance can be accomplished by employing surface texturing of metal substrates on which the absorber paint, CuFeMnO4 is coated [11]; and by use of suitable infrared (IR) transmitting absorber paint binder to reduce thermal emittance [12]
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