Improved VLT & Anti-Static, Super Hydrophilic for Solar Panel「Solar AR Maintenance Re-Coat」※VLT=Visible Light Transmittance※AR=Anti-Reflection

1、 Reduced power generation efficiency due to dirt on solar panels& measures to reduce maintenance cleaning costs
2、 The AR coating transmittance, which decreases with time,
improved by 2 to 3%.

ソーラーパネルの防汚コーティングの重要性
Importance of antifouling coating for solar panels
Currently, the photovoltaic power generation market is rapidly spreading throughout Japan and around the world. In particular,
solar power generation facilities are under construction mainly in the Middle East with an average sunshine duration of 12 hours ormore (5.5 hours in Japan). However, there is a problem of a decrease in the amount of power generation due to sand contamination
because there is a lot of sunshine hours = a desert area where it does not rain. Therefore, in order to maintain power generation
efficiency, the panel is always cleaned, and if it is not cleaned, the amount of power generation will be reduced by 20% due to sandcontamination. (A decrease of 16% is also shown in the California area of the United States.) In addition, the AR coating (Antireflection Coat) for increasing the transmittance of the solar panels made in China gradually decreases from the third year, and thepower generation efficiency decreases accordingly. This time, we have developed a ＰＶ-AR UP Coat with an AR ratio of 2 to 3%,
which is effective in solving the above problems and has an anti-static and super hydrophilic function that is hard to get dirty.

The decrease in power generation due to dirt is 5% to 10% in Japan. 10% to 20% in China and Southeast Asia, 10% to 30% in the
Middle East

After 10months
Uncoated

CoatedIt can be confirmed that the area
where the antistatic antifoulingcoat is applied is effective against
dirt caused by yellow sand.

Uncoated

CoatedIn the desert area where it doesn't rain like the panel in the left picture above, the air is a dry and the sand ischarged and easy to adhere. Solar panel glass is required to have a surface that is difficult to adhere.
Also, regular cleaning maintenance makes it easier to remove dirt due to the super hydrophilic effect, shortening
cleaning time, reducing water usage fees, and using detergents.
Therefore, there are many maintenance benefits by reducing the detergent cost and coating.

In 2018, Global solar power generation 500GW
Top 10 countries in 2018, annual installed and cumulative installedamount of photovoltaic power generation system

Power Purchase Agreement (PPA) bid international ranking

1 China

45GW※２

1 China176.1GW

2 India

10.8GW

2 America

62.2GW

3 America

10.6GW

3 Japan

56.０GW

4 Japan

6.5GW

4 Germany

45.4GW

Ranking 2014~2015 Cents / KWh The third quarter~2016
1
UAE/Dubai
5.85
Chile
2
Jordan6.13
UAE
3
Texas, USA
7.5
Mexico4South Africa
7.6
Peru
5
Brazil
8.1
UAE
6
India
8.75
Jordan7
Panama9.0
South Africa
8
Germany
10.06
Chile
9
India

5 Australia

3.8GW

5 India

32.9GW

Source: "Trends 2016 in PV Applications" in the IEA PVPS (10 May 2016) and,
"Trends 2015 in PV applications" (10 May 2015)

6 Germany

3GW

6 Italy

20.１GW

7 Mexico

2.7GW

7 England

13.0GW

8 Korea

2GW

8 Australia

11.3GW

9 Turkey

1.6GW

9 France

9.0GW

10 Netherlands

1.3GW

10 Korea

7.9GW

８.3GW

EU

115.0GW

Annual installation amountWhole WorldEU

Cumulative installation amount

99.9GW※

Whole World

500GW※Estimated when IEA PVPS non-member countries are included

Cents / KWh
2.91
2.99
3.55
4.9
5.8
6.1
6.5
6.5
6.7

Power generation by fuel in 2040; 12879GW

PV５％ in 2016
６179GW
500GW in2018

Forecast to 2040
Industrial solar 22% 2800GW
Small sunlight 10%1287GW（76.4GW in 2016, 98.9GW in 2017）
97.9GW for IEA PVPS member countries only
{IEA （International Energy Agency）、PVPS（PV Power System Programme)}※2、 53GW in 2017, Decreased in 2018

Remarks
・The top 10 countries installed this year account for 87% of the global PV market.
・ The ratio of PV power generation to electric power demand is about 2.6% worldwide.

China 3.3%, Germany 7.9%, India 5.4%, Honduras 14%, Greece 7.5%
・32 countries achieved over 1GW in cumulative installation.
Among them, 10 countries achieved the introduction of more than 1GW in 2018.

About 30% of power generation will be solar powerSolar power feed-in tariff system and Trends in the number of installed solar power plants in Japan(FIT System)

With the start of the FIT system in 2012, the Solar Plant business in Japan expanded
Trends in electricity sales
The electricity selling price of 10kW
or more.Fixed purchase for 20 years

2009
2010
2011

Electric power company
voluntarily purchases
for about 24 yen

Number of solar power plants installed in Japan
Power generation
scale

Number%

100KW～499KW

1160 plants

11，1％

500KW～999KW

2320 plants

22、3%

１MW～1999KW

4298 plants

41，3%
15，8%

2012

40yen+tax

2MW～2999KW

1648 plants

2013

36yen+tax

3MW～3999KW

220 plants

2014

32yen+tax

4MW～4999KW

144 plants

2015

29yen+tax

5MW～5999KW

82 plants

2016

24yen+tax

6MW～6999KW

32 plants

2017

21yen+tax

7MW～7999KW

34 plants

2018

18yen+tax

8MW～8999KW

49 plants

2019

14yen+tax

9MW～9999KW

22 plants

10MW～14.99MW

138 plants

15MW～19,99MW

73 plants

20MW～29.9MW

88 plants

30MW～39,9KW

40 plants

40MW～

40 plants

Since 2018, it will be purchased for 1kW 20 yen or lessPower generation efficiency measures are becoming
severe.
PV cleaning has also become popular since this time.

1kw 4000 pcs 6000㎡ 10388 plants

Total 962
9，2%

Problems and solutions for AR coating (Anti-Reflection Coat)
AR coating is a coating solution that increases glass transmittance for solar panels. Mainly SiO2 is used, and the transmittance increases byaround 5%. Currently, the world's number one PV panel production is made in China, and the AR coating made in China is applied at the timeof PV panel manufacturing. However, since the second year, the transmittance has been reduced and the power generation efficiency has
been reduced. It has been a big problem around the world now.

First generation of AR coat; 2010-2013
AR coating using SiO2 (silica) of 20nm size. Dirt adherence reduces transmittance, and tiny pinholes(very small hole) can cause a further
decrease in transmittance.

Second generation of AR coat; 2014-2019
AR coating using hollow silica obtained by baking and foaming SiO2 from 550 ℃ to 600 ℃. Currently, the mainstream Chinese AR coat costs
about 12 yen per square meter, and the quality is poor. Due to the variation in the particle size of hollow foamed silica, the quality is notconstant, and a pinhole opens after 2 years, causing dust to adhere to it, further reducing the transmittance. Initially, AR Coat manufactured
by German company or Japanese company were good quality and had no pinholes for more than 20 years. There is a history of withdrawal fromthe market because the coating agent made in Japan and Germany cannot compete with the Chinese AR coating of less than 12m 2 per sqm. For
this reason, the AR coating made in China, which has been used all over the world, has been adopted at a low cost, and the transmittancedecreases from the second year onwards.し、As time passes, the amount of dust attached increases, causing a significant decrease in power
generation efficiency.

The third generation of AR coat; from 2020 onward (solving aftermarket problems after installation)
AR Maintenance Re-coat developed by Sketch in the PV maintenance market is the world's first multifunctional coating solution.
It has an AR of 2% or more, room temperature curing, antistatic function, super hydrophilic function, chemical resistance, hard coat function,and overcoat AR rate increasing function.
Currently, we have partnered with a developer of a machine that can automatically clean solar panels. and are developing a coating robot that
can automatically coat solar panels after they have been cleaned. A system that automatically performs cleaning and coating by machine will
be a big business that is attracting worldwide attention.
There are two types of AR recoats developed by Sketch.
Solar AR Maintenance Re-Coat; AR maintenance recoat using APT and platinum to improve chemical resistance, hard coat properties, antistatic and super hydrophilic function. Even if it is overcoated 5 times or more, the transmittance does not decrease, and it is increased by 2%
or more. This product is ideal for the aftermarket. A machine for coating before installation is also under development

Refractive index 1.5

Refractive index 1.5

AR coating deterioration factors
H2SO4

AR CoatRefractive
index 1.25

Refractive index 1

NaOH

Na ionHNO3

AR Coat; Full-scale entry into aftermarket in 2018
DSM Netherlands listed company sales ¥ 120 billion
The Feature of 「Retrofit Anti-Reflective Coating 」
・A track record of coating 250 million PV modules equivalent to70 GW worldwide.
・ 3% improvement in PV power generation efficiency, Amortization
within 3 years.
・Old modules can be coated after installment.
・Can coat 10,000 PV panels a day by spraying.
・Used in eight types of solar power plants in Germany and Italy,
achieving a 2 to 3% increase in power generation efficiency.
・Dirt can be easily cleaned, reducing the number of cleanings,
cleaning labor costs, and the frequency of use of consumables.
・Stable over 1,000 cleaning cycles (equivalent to biweekly cleaningof about 20 years)
・ Demonstrated 4% increase in electricity at China TUVSUD facility.
・1 module average less than 1 second coating time. Complete theentire array in 1-2 minutes.
・ Obtained JINKO SOLAR warranty
Proven in the field for over 8 years.

It will entry to the United States and China market in 2020.

Solar cell module production volume by region in 2018
EU
USA
Japan 1.3% 2.6%
1.2%
India
1.8%

Canada
1.8%

Others
6.2%

Malaysia
5.1%
Korea
6.5%
Taiwan1.2%

In 2018, solar
cell module
production.
The whole is
116GW

China
72.7%

Prevention of power generation efficiency reduction due to dirt on solar panels &maintenance cleaning cost reduction measures"Antistatic antifouling anti-hydrophilic self-cleaning coat" is applied to reduce
power generation efficiency due to dirt on the solar panel surface and to reduce
maintenance cleaning
AR re-coat with Antistatic antifouling, super hydrophilic self-cleaning function① In regular maintenance cleaning, cleaning with detergent is not necessary. The super-hydrophilic self-cleaning effectmakes it easier to remove dirt by simply washing with water. In addition, the maintenance cost can be reduced by reducing
the number of cleanings.
② Since the power generation efficiency of the solar panel decreases due to dirt, the effect of suppressing the decreasein power generation efficiency can be obtained by applying an antifouling coat to the panel surface.
③ Solar panels have a low installation angle and tend to stick to bird droppings, yellow
sand, and pollen. Therefore, the “AR re-coat” can be solved these problem above because
It has an anti-static function by nano-sized tin oxide (SnO2) and Hardness and chemical
resistance by nano-sized Anmonium Para Tungsten(APT) and nano-platinum (Pt) that
increase the surface hardness and chemical resistance of the solar panel.
④By using a nanomaterial of low refractive material, the visible light transmittance of thesolar panel does not decrease even when applied, so the power generation efficiency does
not decrease. When solar AR recoating is applied, the transmittance increases by 2% or
more, and it is the industry's first AR recoating with antistatic function and super hydrophilic
function.

Uncoated
Uncoated

CoatedCoatedAntifouling measures against the cause of dirt, why it gets dirty, how to get dirty〈 Dirt type 〉〈 Measures analysis 〉〈Ａｎｔｉ-fouling measures with SKETCH products 〉

・ Dust, iron powder and oxide ・・・ Since it is an inorganic stain,
it cannot be decomposed with a photocatalyst 。
Reduces adhesion of dirt with・Ｃａｒｂｏｎ， Coal ash, soot, exhaust gas ・・・Even organic stains cannot be decomposed
antistatic function.
with a photocatalyst.
・ Pollen, sap, oil stain ・・・Decompose with photocatalyst or clean easily.
Easy to clean with super hydrophilic and hard coat.
・ Bird droppings and insects ・・・Increase chemical resistanceand decompose with hard coat or photocatalyst.
・ deterioration color fading due to chemical changes caused
Improve chemical resistance.
by NOX, SOX, acid rain and chemicals ・・・Increase chemical resistance.
・ Deterioration and fading due to UV rays ・・・Use UV protection or inorganic coating.
・ Dirt caused by mold ・・・Antibacterial measures or photocatalytic treatment
Inorganic coating
・ Deterioration and fading due to heat and oxidation ・・・ Coat inorganic coating solution from organic .
・ Salt damage due to sodium chloride and mineral adhesion ・・・Easy to remove due to chemical resistance and hard coat.
Increase chemical resistanceand hard coat properties

→
→

→

→
→

→
→
→

→

Solve all the above problems 。
The raw material of
AR Maintenance Re-Coat
SiO2：Improved transmittance,
super hydrophilic performance
SｎO2：Anti-Static, Super Hydrophilic
PT: Chemical resistance, hard film
Improved antifouling performance
APT: Chemical resistance, hard film
Improved photocatalytic
performance and adhesion
Super-hydrophilicity measurementat High Environmental Engineering Co., Ltd.

１）Single nano-sized SiO2 and SnO2 create a nano-sized fine irregular surface
on the base material, improving the transmittance and exhibiting a superhydrophilic effect with a water droplet contact angle of 5 degrees or less.
2) Anti-static effect by SnO2 that extremely reduces the adhesion of
inorganic soil, APT added to improve anti-static, hard coat properties also
improved
3) Addition of APT and PT improves chemical resistance, adhesion andweather resistance. Also, due to the photocatalytic effect, oil stains aredecomposed, and super-hydrophilic performance is improved.
4) All nanomaterials are 100% inorganic metal oxide, so there is no
deterioration over time. Safe and high weather resistance.
5) High adhesion achieved with ultra-thin film with a dry film thickness of 200
nanometers or less. High performance at low cost.

Contact angle 3 degrees6) Immediate effect at room temperature and quick drying.

What is super hydrophilicity?
Which does it get dirty between super-hydrophilic and water repellency?
In the case of Plastic

Super-hydrophilic
is a water droplet
contact angle of
5 to 10 degree.

Water repellencymeans a water droplet
contact angle of 75 to
90 degrees

Drops water droplets on the substrate and measures the contact angle between the substrate and the water
droplets. The water droplet contact angle is from 40 degrees or less to hydrophilic, and 10 degrees or less is superhydrophilic. The waterdrop contact angle is 70 ~ 100 degrees water repellent, 110 ~ 180 degrees super water repellent.
Painting

Dirty

Water drop angle（°）

Dirtiness by water drop angle

Teflon110～115

Easy to take off the dirt

Fluorine resin paint100～105

Easy to adhere the dirt

Silicone paint100～105

Easy to adhere the dirt

Acrylic urethane paint85

Easy to adhere the dirt

NOF Bell clean paint30～40

Difficult to adhere the dirt

Titanium oxide coating～10～

Photo catalyst/Super
hydrophilic

AR Maintenance Re-CoatLess than 3～5Lightnessdifference
Silicone paint

Acrylic urethane paint
Sketch ProductAntistatic/Super hydrophilic

Carbon dirt is intentionally attached to the substrate andsprayed with water to investigate the relationship between watercontact angle and carbon decontamination,
Result) The smaller the water droplet contact angle, the harder itgets and the easier it is to remove it.

Clean

Super hydrophilicity is absolutely hard to get dirty
Contact angle of coating film

Theoretical explanation and features of super hydrophilic self-cleaning function & antistatic function
It is too late after it gets dirty. The best priority is hard to adhere dirt and easy to remove dirt.
The raw material

１, Anti-Static function

SiO2：Improved transmittance,
super hydrophilic performance
SｎO2：Anti-Static, Super Hydrophilic
PT: Chemical resistance, hard film
Improved antifouling performance
APT: Chemical resistance, hard film
Improved photocatalytic
performance and adhesion～200nm２, Super Hydrophilic Self-Cleaning

v

v
v
v

v

v
v
v

v
v

v

v
v

Antistatic function by electronic conductivity
Ultrafine tin oxide (SnO2) has many free electrons, lowelectrical resistance, surface resistance (up to 10 9 Ω / □),does not adhere fine dust and particles floating in the air, dust,
exhaust gas It is hard to stick. Especially in China, the carbon,
coal ash, and yellow sand are so dirty that they cannot be
decomposed by the photocatalytic function, so the antifoulingeffect cannot be expected. Rather than a photocatalyst that
decomposes attached dirt, Super-hydrophilic & anti-static
function is the most effective because it is hard to get dirt andeasily removes dirt.

cv v

Substrate： Solar Panel, Glass, Mirror※What is fractal theory?
The theory that the effect of hydrophilicity becomes stronger due to fineirregularities on the surface. If the unevenness is evenly arranged, it
becomes super water-repellent, and if it is unevenly arranged, it becomessuper-hydrophilic. We have succeeded in creating irregularities with a film
thickness of 200 nanometers or less by using several types of nano-silica
and single nanomaterials. As a result, a super-hydrophilic film is always
formed without photocatalytic function. Substrates such as glass,polycarbonate, and stainless steel appear flat on the surface, but in fact,
there are fine irregularities that are not visible. Therefore, by using ourbinder technology, it is possible to adhere to various materials by controllingsilica and tin oxide of various sizes from 2nm to 10nm. In addition, since
silica with a very small particle size is used, the photocatalyst and antistatic
nanomaterial can be brought out on the surface, so that the function can be
performed very efficiently.

Synergistic super-hydrophilic and powerful self-cleaning
properties based on fractal theory * of fine particles
using several types of silica
Rinse dirt with only rain and running water. In addition, oilstains and organic stains are prevented from sticking, and theattached stains are floated and washed with a superhydrophilic effect.

３, Quick drying at room temperature
Quickly dry after coating, effective immediately

４, Hard Coat film and Chemical resistance
Easy cleaning of acid rain
Easy cleaning of bird droppings and insects

５, Increased transmittance
By combining single nano and 15 nano class materials,
Transmittance improved by 2-3%

６, High transparency and low refraction
The reflection suppressing,visible light transmittance decreases prevention

2 type of products and characteristics
AR Maintenance Re-Coat・・ for after market of existing PV①ＳｉＯ２(Nano sized of Silica)・・・・・・ Increased transmittance, super hydrophilic adhesion binder function②ＳｎＯ２(Nano sized of Tin Oxide)・・・・・Anti-Static function③APT(Nano sized of Ammonium Para Tungsten) ・・・ Photocatalyst④Pt(Nano sized of Platinum)・・・・・・・・ Chemical resistance and hard coat properties⑤Methanol & Distilled water

Improved by ２,9％

VLT
９０,8％

VLT
９3,7％

Solar Maintenance AR Recoat uses multiple silica particles of 10 nanometers or less. Due to the properties of inorganic
100% silica binder, it has high transparency, room temperature curing, quick drying, and super hydrophilicity. In addition,
the antistatic functional material tin oxide = SnO2 is used, and APT = Ammonium Para Tungsten and Pt = platinum are used
to improve chemical resistance and ultra hard coat without reducing visible light transmittance(=VLT). VLT is improved by
2-3% or more.= Undo reduction of visible light transmittance due to deterioration of AR coating.

111) AR maintenance recoat (APT) transmittanceincrease verification
2019年10月19日
The conventional antistatic super hydrophilic antifouling coating for solar panels, “Solar Self-Maintenance Coating,” used
TiO2 to improve weather resistance on glass substrates. In order to further improve functionality, the new material APT, which
has been studied two years ago, has finally become stable, so we will introduce as an AR Maintenance Re-Coat with APT .The
characteristics are described in the following.

～ Functions of APT type compared to TiO2 type ～1. Improved wear resistance
Although the TiO2 type has acertain level of wear resistance, it
has been confirmed that thehydrophilicity of the TiO2 type isreduced by dry friction due to thecoating film structure using surface
irregularities.
* There is no problem with wet
friction in the normal range such as
maintenance.

2. Improved Transmittance

Uncoated Glass
90.8±0.3

About1.5%up

Coated Glasswith TiO2
92.7±0.5

Tio2 surface
after friction↓
Water-repellent

TiO2

APT surface
after friction↓
Hydrophilicity

APT

A state where only the upper part is drypolished. Compared to tio2, which has
become water repellent, APT maintains ahydrophilic state. APT was passed a testof the standard 500 times dry polishingof glass processing manufacturers that
Tio2 did not pass.

About 2～2.5%up

Coated Glasswith APT93.6±0.5

The AR Maintenance Re-coatincreases the transmittancedepending The conventional Tio2 isimproved by 1% to 1.5%, but APT
can be expected to improve by
about 2%.※ The above figures are
not guaranteed values because
they depend on the coating method
and the film formation conditions.

2) AR Maintenance Re-Coat transmittance2019年10月19日
increase verification Part 2
The verification of fluctuations in VL transmittance rate by recoating

Uncoated

Apply twiceStart

3rd time

4th time

5th time

２%UP↑

２.9%UP↑

3.4%UP↑

3.6%UP↑（Compared with Uncoated)（Compared with Uncoated) （Compared with Uncoated) （Compared with Uncoated)

6th time

7th time

8th time

9th time

10th time

4.1%UP↑

4.9%UP↑

4.8%UP↑

0.8%Down↓

1.2%Down↓（Compared with Uncoated)（Compared with Uncoated) （Compared with Uncoated) （Compared with 8th time)（Compared with 8th time)

Even if it recoated, VLT didn’t decrease. But It decreased after 9th time

The weather resistance test results by major glass manufacturer

Uncoated-

Surface resistance（Ω/□）
Before the test

After the test

May 2013 conducted

SSMC※
5.8E+09

90.3

92.9

Contact angle (°)-

0.0

Surface resistance（Ω/□）-

7.5E+08

Visible light transmittance (%)

-

92.2

Contact angle (°)-

3.3

Visible light transmittance (%)※SSMC＝ Solar Self Mainte Coat

■Weathering test content

・Weathering test of 1,000 hours at 85% humidity under 85 ℃ room temperature＝10～15 years equivalent（ Weathering
test of strict criteria to determine whether to adopt as processed products ）・It checks the following three items degradation situation of the membrane surface by the elution of sodium ions.
① Surface resistance value = antistatic effect② Visible light transmittance = transparency ③ Contact angle = super-hydrophilic■ Acceptance criterion■Test results
10Ω/□・ Surface resistance value : less than １０
・ Visible light transmittance

⇒

9Ω/□

10

８Ω/□

～１０

:More than ９０％⇒ 92.9％～92.2％

・ Water droplet contact angle :Less than ２０° ⇒00°～ 3.3°■judgment
Pass ◎
Pass ◎
Pass ◎■ Conclusion ：As for application market, it is passed weathering test equivalent to
14
10 ~15 years

Coating Application result
100 sqm in Ibaraki, Japanin Nepal

310 sqm in Kagoshima, Japan

70sqm in Kagoshima

162 sqm in Korea
100pc of panels

1500 sqm in Osaka, Japan
1000pc of panels

in Thailand

CoatedUncoated15

Coating 施工事例
Application result
Applied for 4000sqm in Tochigi, Japan

Step① Glass Cleaning

Step②Wash with water
and wipe off

Step③ Coating

Step④Dry and storage

Applied for 198pc panels(508.8sqm) in Okayama, Japan16
Step① Glass Cleaning

Step②Wash with water
and wipe off

Step③ Coating

In Nepal, Coating and selling Solar panel with antifouling Coat.

Snow melting promotion effect in Xuzhou, China

Confirmation of the thaw promoting effectafter 3days of 1,000㎡ coating in China
Snow surface becomes a lump, it was easy to slip off.
ReasonIts function is effectively demonstrated and dust and the like in the air hardly
adhere to the surface. In addition, even if it gets dirty, it is possible to self clean
the surface stain due to rainwater or the like due to the superhydrophilic function.
When water is applied to the uncoated surface, it is in a water repellent state,
and the dirt becomes a water spot remaining in the polka dots. If this is repeated
for a long time the surface becomes dirty,Resulting in a decrease in power
generation efficiency.Since the coated surface is in a superhydrophilic state witha contact angle of water of 5 degrees or less,It can easily wash away. Therefore,
it is difficult for water spot to be formed, and reduction in power generation
efficiency can be reduced.

Accelerated dissolution test

CoatedUncoated

Prepare a glass withhalf of this productapplied and half
unapplied, put it in afreezer with water.
Freeze the coatedsurface as a thin film. →It is easy to dissolve
The uncoated surface
freezes as a lump. →hard to melt
I could confirm theresult.

Freeze in thinmembraneCakefreezing

CoatedUncoated

Already Melt

Still ice