Nano-Materials Solar Selective Paint for Flat Plate Collectors Nidal Y Abdalla National Energy Research Center n.abdalla@nerc.gov.jo

Contents Solar Radiation Spectrum. Absorber Coating techniques Selective Coating Versus Selective Paints. Project Procedures Preparing The Specimens and Emittance Test Preparing The Flat Plate Solar Collectors Efficiency Test of The Collectors at RSS Solar Lab Results and Discussion Conclusions

Solar Radiation

Solar Spectrum X &  Rays Solar radiation Radio Rays تزداد طول الموجة الأشعة تحت الحمراء Infrared radiation الأشعة المرئية 0.4 – 0.8 m 8 km 10-8 m الأشعة الحرارية Thermal radiation 0.3 –2.5 m Solar radiation

Absorber Coating techniques Solar collector coating technique can be divided into two types : Non-selective coatings technique: Absorber with high absorptance , , as well as high Emittance, , which is found in all local solar collector manufactured in Jordan using ordinary black paints (with λ1 ≈ 0.95 and  λ2 ≈ 0.94).

Absorber Coating techniques Selective coatings deposited by chemical or electrical processes have a high  λ1 and low  λ2 (e.g., in black chrome surface,  λ1 ≈ 0.95 and  λ2 < 0.3) so they are more attractive for use in solar collectors. Efficient absorber has high absorption of irradiation and low emission of heat radiation

Absorber selective coating: Black Nickel Black chrome Physical vapor deposition (PVD), TINOX

Selective Coating Versus Selective Paints Absorber selective coating has lower Emittance than selective paint. For absorber with selective coating  λ is less than 0. 3 (Ti sputtered on Cu, λ =0.02 ). For absorber with selective painting  λ is between 0. 7 and 0.3

Selective Coating Versus Selective Paints In flat plate collector and for absorber temperature lower than 100° C, the collector heat loss is reduced dramatically if  is reduced from 0.95 to 0.3, but a further reduction in  from 0.3 to 0.1 brings only a small benefit.

Selective Coating Versus Selective Paints Therefore the selective paints are cheaper and easier to apply look more attractive for flat plates. It doesn’t need complicated chemical or electrical processes.

Project Objective The aim of this study is to investigating the thermal impact of the modified paints on the collector performance by adding certain nano-materials to the dull carbon black paint

Project Procedures Dull black carbon paint was first prepared by grinding the carbon material into non particles and was well mixed with especial solvent called turpentine. Preparing of the nano-particles was carried out by ICC at RSS. Certain nano particles were prepared and grinded to smaller size and mixed with the carbon black paint formulas.

Project Procedures Different specimens surfaces were painted by the following processes: The specimens surface were cleaned with chemical cleaner to ensure a good paint-surface adhesion. A panel were pained with dull black carbon and considered as a base reference specimen.

Several specimens with different nano-materials (modified paints) were painted. All specimens were dried by using oven at 200 C.

Preparing The Specimens For Emittance Test

Emittance Test of the Specimens Using Emissometer

Measurement Results

Preparing The Flat Plate Solar Collectors Two solar collectors were manufactured at NUR company . One collector was painted with dull black paint. The second one was painted with the new modified (selective) paint. Dimensions, thermal insulation and all other design parameters are kept the same for all collectors.

Design parameters for the collectors

Efficiency Test of The Collectors at RSS Solar Lab

Results and Discussion 67% 64%

Results and Discussion It was found that the optical collector efficiency was increased by about 4.5%. Moreover, the efficiency slope was improved by about 15%

Results and Discussion The actual improvement can be found by estimating the annual useful heat that can be gained using each of the collectors as applied for domestic hot water system. Shortcut method program available, F-Chart software was used.

Results and Discussion The results shows that annual difference heating delivered about 277 kWh per square meter of collector. The annual thermal performance for the modified collector was improved around 11% over the existing local manufactured collector.

Results and Discussion This modification on solar flat plate collector will increase the market penetration of the local manufactured so that it will competes the exported solar collector.

Results and Discussion  Referring to survey which was made by NERC in 2009, the annual solar collector installed by the local manufacturing industries is about 20,000 m². Therefore, annual reduction of CO2 emission from the modified-painted collectors (20,000 m²) will be more than the conventional painted solar collectors by an amount of 3,123 ton per year

Conclusions  Adding nano-chromium particles to the carbon black paint modify the collector as follows: The optical collector efficiency was increased by about 4.5%. The efficiency slope was also improved by about 15%. The annual thermal performance for the modified collector was improved around 11% over the existing local manufactured collector.

Thank You