Solar Energy 263 (2023) 111956
0038-092X/© 2023 The Author(s). Published by Elsevier Ltd on behalf of International Solar Energy Society. This is an open access article under the CC BY-NC-ND
On site renovation of degraded PV panels – Cost and environmental
, Igor Tyukhov
, Vaclav Beranek
Czech University of Life Science, Prague, Czech Republic
San Jose State University, San Jose, USA
Solarmonitoring sro, Prague, Czech Republic
Life-time of PV power plants
Renovation technology of PV panels
The encapsulation of photovoltaic (PV) panels determines the trouble-free lifetime of the panels. The quality of
PV panel encapsulating components has signicantly decreased over the last 25 years. Consequently, large
quantities of PV panels worldwide are experiencing degradation or damage much earlier than expected.
To address this issue, an on-site renovation technology for PV panels has been developed, which involves pre-
deposition diagnosis and polydimethylsiloxane (PDMS) lm deposition. This technology substantially prolongs
the real eld lifetime of PV panels. In terms of carbon footprint, PV panel renovation is over a hundred times
more effective compared to PV panel replacement. It is also a protable solution.
The trouble-free lifetime of PV panels is determined by their
encapsulation by lamination process. However, due to intense market
competition for the production of the cheapest modules, both the
quantity and quality of encapsulating components have decreased over
the past 25 years. For instance, 25 years ago, the front glass thickness of
PV panels ranged from 4.0 to 3.2 mm. Recently, it has been decreased to
3.2–2.8 mm range despite the PV panel area being four times larger. At
glass/glass PV panels the usual front glass thickness was 3.2 mm but it
was decreased to 2.0 mm or even to 1.6 mm. Similarly, the height of
typical PV panel frames was 40–50 mm 25 years ago, but it now ranges
from 30 to 35 mm, despite the PV panel area being four times larger.
Additionally, the use of less durable lms such as PVDF (polyvinylidene
uoride), PET (polyethylene terephthalate), PA (polyamide), etc., has
become common for the polymer-based backsheets, whereas it origi-
nally used the best quality polyvinyl uoride (PVF) lm. Moreover, the
typical PV array system voltage has increased from about 600 V DC to
900 V DC, and more recently, up to 1500 V DC. Therefore, the quality of
insulation and encapsulation materials should be increased rather than
decreased. Furthermore, many new PV plants have been installed in
demanding tropical locations, leading to a decrease in ground imped-
ance (Risol) in real eld conditions due to PV panel back sheet
It should be noted that laboratory simulations and accelerated
testing are not equivalent to real eld tests. Authoritative declarations
about a 25–30 year lifetime of PV panels based on a few years of real
eld tests are also not relevant. Additionally, our experiments conrm
that the ground impedance (Risol) of PV panels in eld conditions (wet
and dirty) is typically reduced by more than 1000 times compared to
laboratory tests of the same PV panel after cleaning and drying.
Although reduced ground impedance is a major factor, it is not the only
source of PV panel degradation. However, this article does not focus on
describing all PV panel degradation models.
Moreover, it is important to note that PV panels are connected in
series to inverters (usually 20 panels), where a failure of a single PV
panel causes the disconnection of the remaining 19 panels in the string,
resulting in a multiplication effect . Consequently, the failure of 5%
of PV panels in a PV power plant can cause a substantial reduction in
Recently, reports have been published indicating that many IEC
61215 certied PV panels, particularly those located in demanding or
tropical climates, have a lifespan of less than 12 years [2–5]. In some
cases, this lifespan is even shorter, lasting less than 4 years [6–10], with
an annual degradation rate exceeding 2% (see Table 1). These panels
reach a total output power degradation limit of 80%, despite commer-
cial leaets declaring a PV panel lifetime of 25–30 years until 80%
degradation. Table 1 illustrates two degradation groups: the rst group
* Corresponding author.
E-mail addresses: firstname.lastname@example.org (V. Poulek), email@example.com (I. Tyukhov).
Contents lists available at ScienceDirect
journal homepage: www.elsevier.com/locate/solener
Received 6 July 2023; Received in revised form 2 August 2023; Accepted 16 August 2023
Solar Energy 263 (2023) 111956
with a panel lifetime of up to 12 years and the second group with a
lifetime of up to 4 years. There are numerous additional reports on
degradation, but they often remain unpublished due to the condential
nature of the data following early failures in PV power plants. An
example of such rapid degradation occurred in an 86 MW PV power
plant in South Africa, where substantial output power reduction was
observed just 3.5 years after the plant’s opening, caused by PV panel
back sheet degradation. This example aligns with the second degrada-
tion group, although exact data remain condential . Another
valuable source of degradation data was measured and calculated in
Even in the moderate climate of Europe [14–17], fast PV panel
degradation ranging from 7 to 12 years is often associated with back
sheet degradation, leading to a reduction in ground impedance (Risol).
International Energy Agency (IEA) report  evaluated possibility to
replace PV panels in 10 years period. The high degradation rates result
in signicantly increased expenses for replacing damaged PV panels in
PV power plants. As a result, some panels need to be dismantled after
Degradation of usual design glass/polymer-based backsheet c-Si PV panels in demanding climate.
Location Ref.No. Ghana  India  Algeria  Algeria  Morocco  India  Thailand  Senegal  S.Africa 
Annual degradation 3.19% 2.5% 3% 2.6% 2.6% 20% 2.7% 2.96% 5.5%
Outdoor exposure 12 years 10 years 11 years 11 years 3 years 2.5 years 3 years 4 years 3 years
Fig. 1. Picture of renovation PDMS lm on back side of PV panel.
Fig. 2. Real eld (wet) Risol of PV panels before and after PV panel renovation.
V. Poulek et al.
Solar Energy 263 (2023) 111956
only 3 to 12 years, which is well before the expected lifetime of 25 to 30
years. However manufacturers increased workmanship/defect warranty
period from 5 years to 12-15 years within last decade. Naturally, this
has corresponding economic consequences .
Therefore, servicing and maintaining new PV power plants, espe-
cially in harsh climates characterized by high temperatures and hu-
midity, pose signicant challenges. However, a new restoration method
has the potential to address these issues.
2. PV panel renovation
The standard approach of replacing damaged PV panels with new
ones is expensive and also not environmentally friendly in terms of
carbon footprint. Several technologies for onsite PV panel renovation
have been tested [1,16]. Some of these technologies utilize a thin pol-
ydimethylsiloxane (PDMS) lm, approximately 0.1 mm in thickness, as
depicted in our Fig. 1. PDMS is a hydrophobic material known for its
excellent thermal stability, with a thermal resistance of 250 ◦C and a
Relative Thermal Index (RTI) of 150 ◦C. It also exhibits good resistance
to ultraviolet radiation. Interestingly, PDMS is the same material used in
high-temperature, long-lasting PV panel lamination technology .
We have developed a new PV panel renovation process that includes
not only on-site thin 0.1 mm PDMS lm deposition technology but also a
comprehensive on-site PV panel diagnosis, including measurements of
ground impedance (Risol), delamination, and other factors, both before
and after the protective lm deposition. The two component PDMS has
been deposited on site by spraying method. Fast cure (30 min at tem-
perature 25◦Celsius) PDMS was used. The lm thickness was measured
by micrometer gauge. The main method to check the renovation lm
quality has been regular testing of ground impedance (Risol) in real eld
(wet) conditions. To double check the renovation quality early morning
inverter switch on time was monitored. Once there are troubles with low
Risol the inverters are switched on several hours later as the inverters
have internal Risol safety control . Besides Risol tests visual check of
chalking and edge delamination was performed.
To evaluate the effectiveness of our renovation process, we selected
two test sets comprising 40 rst-tier (bankable) PV panels rated at 250 W
each. These panels were installed at a 2 MW PV power plant situated in a
moderate climate region of central Europe. The rst set consisted of
damaged PV panels that were repaired using a 0.1 mm thin PDMS lm
with fast curing properties. The repaired panels were observed for a
period of 5 years. As shown in Fig. 2, the real-eld (wet) PV panel
ground impedance (Risol) was successfully restored after the renovation
and remained nearly unchanged throughout the 5-year observation
The tests demonstrate that the lifetime of repaired PV panels could be
extended by 5 years or even more. The low cost renovation can be
performed repeatedly in 5–7 years period. In contrast, the second set of
PV panels without renovation experienced signicant degradation after
5 years, leading to non-repairable failure. This failure was characterized
by the presence of electric discharge channels between the PV panel’s
internal busbars and the grounded PV panel frame (Fig. 3), with Risol
values falling below the critical threshold of 25 Mohm. At the beginning
of the test (10 years of operation) Risol of 18 panels was below 25Mohm.
At the end of the test (15 years of operation) Risol of all 40 PV panels was
well below 25Mohm. Furthermore, delamination of the panel edges
occurred, allowing water penetration and degradation of the back-
surface laminate, resulting in cracks and chalking. It is crucial to
conduct PV panel renovation within approximately one year after a
rapid decrease in Risol is observed. Once an electric discharge channel is
formed, the PV panel becomes irreparable. To date, a total of 41 MW of
PV panels have been successfully repaired using the thin siloxane lm
3. The carbon footprint
The carbon footprint is increasingly becoming an important crite-
rion. We can compare the carbon footprint of a new replacement PV
panel with the carbon footprint of the PDMS renovation lm as follows:
a) The manufacturing carbon footprint  of a typical rst-tier
(bankable) PV panel, sized 1 ×1.6 m and with a power output of 300
W (weighing approximately 20 kg), results in 120 kg CO2 eq. More
recent report  on c-Si PV panel carbon footprint shows similar
b) The manufacturing carbon footprint of a typical 0.1 mm thin
polydimethylsiloxane lm , sized 1 ×1.6 m (weighing 0.15 kg),
results in 0.94 CO2 eq.
The replacement/renovation carbon footprint ratio is 121 to 1, and
the replacement/renovation weight ratio is 133 to 1 (see Table 2). PV
panel renovation is also signicantly less expensive compared to PV
panel replacement, with a replacement/renovation cost ratio of 11 to 1.
Please refer to Table 2 for more details.
A brief review of publications on the reliability of photovoltaic
modules reveals that the modules’ service life is often shorter than the
manufacturer’s warranty. One of the factors contributing to the reduced
service life of solar modules is the quality of materials used on the back
side of the modules.
The proposed technology for on-site upgrading of solar PV modules is
Fig. 3. Discharge channel between internal solar panel busbar and grounded
PV panel frame.
PV panel replacement and renovation comparison (size 1x1.6 m, power 360 W.
Weight of replacement/
Carbon footprint of replacement/
Estimated lifetime of replacement/
Replacement/renovation cost (material,
PV panel replacement by
20 kg ~ 120 kg CO
eq About 7–10 years ~ 120 USD
PV panel renovation by
0.15 kg ~ 0.94 kg CO
eq About 5–7 years ~ 11 USD
V. Poulek et al.
Solar Energy 263 (2023) 111956
approximately 11 times more cost-effective than replacing the entire
modules and about 120 times more effective in terms of carbon footprint
reduction. The PDMS coating is stable for more than 5 years of exposure
and allows the modules to restore their electrical insulation properties.
Therefore, for PV power plant owners (end users), renovating PV panels
proves to be a protable and environmentally sound solution.
Declaration of Competing Interest
The authors declare that they have no known competing nancial
interests or personal relationships that could have appeared to inuence
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