Transcript Solar Water Heating Systems: Improvement and Potential

Nano-Materials Solar Selective Paint for
Flat Plate Collectors
Nidal Y Abdalla
National Energy Research Center
[email protected]
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
0.3 –2.5 m
10-8 m
‫تزداد طول الموجة‬
8 km
‫األشعة المرئية‬
‫األشعة تحت الحمراء‬
0.4 – 0.8 m
Infrared radiation
‫ األشعة الحرارية‬Thermal 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 nanomaterials 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 nanoparticles 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 paintsurface 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
No.
1
2
3
4
5
6
7
Surface ID
Carbon black paint
(Reference)
Iron (Fe )
Copper (Cu )
Zinc (Zn )
Chromium (Cr)
Titanium (Ti)
Cr-Ti combination
Thickness
(Micron)
100
Emissivity (ε)
100
100
100
100
100
100
0.91
0.85
0.89
0.79
0.81
0.86
0.90
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
64%
67%
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