On site renovation of degraded PV panels – Cost and environmental effective technology

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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
license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
On site renovation of degraded PV panels – Cost and environmental
effective technology
Vladislav Poulek
a
, Igor Tyukhov
b
,
*
, Vaclav Beranek
c
a
Czech University of Life Science, Prague, Czech Republic
b
San Jose State University, San Jose, USA
c
Solarmonitoring sro, Prague, Czech Republic
ARTICLE INFO
Keywords:
Life-time of PV power plants
Encapsulation
Renovation technology of PV panels
Polydimethylsiloxane
Carbon footprint
ABSTRACT
The encapsulation of photovoltaic (PV) panels determines the trouble-free lifetime of the panels. The quality of
PV panel encapsulating components has signicantly 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 protable solution.
1. Introduction
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
degradation.
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 conrm
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 [1]. Consequently, the failure of 5%
of PV panels in a PV power plant can cause a substantial reduction in
energy production.
Recently, reports have been published indicating that many IEC
61215 certied 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 leaets 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: poulek@tf.czu.cz (V. Poulek), igor.tyukhov@sjsu.edu (I. Tyukhov).
Contents lists available at ScienceDirect
Solar Energy
journal homepage: www.elsevier.com/locate/solener
https://doi.org/10.1016/j.solener.2023.111956
Received 6 July 2023; Received in revised form 2 August 2023; Accepted 16 August 2023

Solar Energy 263 (2023) 111956
2
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 condential
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 condential [11]. Another
valuable source of degradation data was measured and calculated in
Qatar [12,13].
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 [18] evaluated possibility to
replace PV panels in 10 years period. The high degradation rates result
in signicantly increased expenses for replacing damaged PV panels in
PV power plants. As a result, some panels need to be dismantled after
Table 1
Degradation of usual design glass/polymer-based backsheet c-Si PV panels in demanding climate.
Location Ref.No. Ghana [2] India [3] Algeria [4] Algeria [5] Morocco [6] India [7] Thailand [8] Senegal [9] S.Africa [10]
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
3
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 [17].
Therefore, servicing and maintaining new PV power plants, espe-
cially in harsh climates characterized by high temperatures and hu-
midity, pose signicant 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 [19].
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 [1]. 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
period.
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 signicant 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
method.
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 [20] 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 [21] on c-Si PV panel carbon footprint shows similar
results.
b) The manufacturing carbon footprint of a typical 0.1 mm thin
polydimethylsiloxane lm [22], 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 signicantly 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.
4. Conclusion
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.
Table 2
PV panel replacement and renovation comparison (size 1x1.6 m, power 360 W.
Weight of replacement/
renovation item
Carbon footprint of replacement/
renovation item
Estimated lifetime of replacement/
renovation item
Replacement/renovation cost (material,
labor, transport….)
PV panel replacement by
new one
20 kg ~ 120 kg CO
2
eq About 7–10 years ~ 120 USD
PV panel renovation by
PDMS lm
0.15 kg ~ 0.94 kg CO
2
eq About 5–7 years ~ 11 USD
V. Poulek et al.

Solar Energy 263 (2023) 111956
4
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 protable 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 inuence
the work reported in this paper.
References
[1] Poulek, V., ˇ
Safr´
ankov´
a, J., Cern´
a, L., Libra, M., Ber´
anek, V., Finsterle, T.,
Hrzina, P., 2021 Mar. PV panel and PV inverter damages caused by combination of
edge delamination, water penetration and high string voltage in moderate climate.
IEEE J. Photovoltaics 11 (2), 561–565. https://doi.org/10.1109/
JPHOTOV.2021.3050984.
[2] Atsu, D., Seres, I., Aghaei, M., Farkas, I., 2020. Analysis of long-term performance
and reliability of PV modules under tropical climatic conditions in sub-Saharan.
Renew. Energy 162, 285–295.
[3] Sastry, O.S., Saurabh, S., Shil, S.K., Pant, P.C., Kumar, R., Kumar, A.,
Bandopadhyay, B., 2010. Performance analysis of eld exposed single crystalline
silicon modules. Sol. Energy Mater. Sol. Cells 94 (9), 1463–1468.
[4] Kahoul, N., Cheghib, H., Sidrach-de-Cardona, M., Affari, B.C., Younes, M.,
Kherici, Z., 2021. Performance degradation analysis of crystalline silicon solar cells
in desert climates. Energy Sustain. Dev. 65, 189–193.
[5] Bouraiou, A., Hamouda, M., Chaker, A., Mostefaoui, M., Lachtar, S., Sadok, M.,
Boutasseta, N., Othmani, M., Issam, A., 2015. Analysis and evaluation of the impact
of climatic conditions on the photovoltaic modules performance in the desert
environment. Energ. Conver. Manage. 106, 1345–1355.
[6] Bouaichi, A., Merrouni, A.A., Hajjaj, C., Messaoudi, C., Ghennioui, A.,
Benlarabi, A., Ikken, B., El Amrani, A., Zitouni, H., 2019. In-situ evaluation of the
early PV module degradation of various technologies under harsh climatic
conditions: The case of Morocco. Renew. Energy 143, 1500–1518.
[7] Sharma, V., Chandel, S.S., 2016. A novel study for determining early life
degradation of multi-crystalline-silicon photovoltaic modules observed in western
Himalayan Indian climatic conditions. Sol. Energy 134, 32–44.
[8] Thien Le, N., Asdornwised, W., Chaitusaney, S., Benjapolakul, W., 2021. Annual
degradation rate analysis of mono-Si photovoltaics systems in Thailand using the
mixed effects method. IEEE Access 9, 101335–101343.
[9] Ndiaye, A., K´
eb´
e, C.M.F., Charki, A., Ndiaye, P.A., Sambou, V., Kobi, A., 2014.
Degradation evaluation of crystalline-silicon photovoltaic modules after a few
operation years in a tropical environment. Sol. Energy 103, 70–77.
[10] Vandyk, E., Chamel, J., Gxasheka, A., 2005. Investigation of delamination in an
edge-dened lm-fed growth photovoltaic module. Sol. Energy Mater. Sol. Cells 88
(4), 403–411.
[11] Heubl, B., 2020 Oct. Millions of solar PV panels could fail or degrade prematurely
and may even be at risk of res. But no one knows exactly where they are or how
big the problem is. Eng. Technol. 15 (9), 38–41. https://doi.org/10.1049/
et.2020.0904.
[12] Abdallah, A.A., Ali, K., Kivambe, M., 2023. Performance and reliability of
crystalline-silicon photovoltaics in desert climate. Sol. Energy 249, 268–277.
[13] Aly, S.P., Ahzi, S., Barth, N., Abdallah, A., 2020. Numerical analysis of the
reliability of photovoltaic modules based on the fatigue life of the copper
interconnects. Sol. Energy 212, 152–168.
[14] Buerhop-Lutz, C., Stroyuk, O., Pickel, T., Winkler, T., Hauch, J., Peters, I.M., 2021.
PV modules and their backsheets - A case study of a Multi-MW PV power station.
Sol. Energy Mater. Sol. Cells 231, 111295.
[15] Eder, G.C., Voronko, Y., Oreski, G., Mühleisen, W., Knausz, M., Omazic, A.,
Rainer, A., Hirschl, C., Sonnleitner, H., 2019. Error analysis of aged modules with
cracked polyamide backsheets. Sol. Energy Mater. Sol. Cells 203, 110194.
[16] Voronko, Y., Eder, G.C., Breitwieser, C., Mühleisen, W., Neumaier, L.,
Feldbacher, S., Oreski, G., Lenck, N., 2021. Repair options for PV modules with
cracked backsheets. Energy Sci. Eng. 9 (9), 1583–1595.
[17] Libra, M., Mr´
azek, D., Tyukhov, I., Severov´
a, L., Poulek, V., Mach, J., ˇ
Subrt, T.,
Ber´
anek, V., Svoboda, R., Sedl´
aˇ
cek, J., 2023. Reduced real lifetime of PV panels –
Economic consequences. Sol. Energy 259, 229–234.
[18] International Energy Agency (IEA) PVPS report, https://iea-pvps.org/wp-cont
ent/uploads/2021/11/IEA_PVPS_T12_Preliminary-EnvEcon-Analysis-of-modu
le-reuse_2021_report_slides_summary.pdf. 2021, pp.30-34.
[19] Poulek, V., Strebkov, D.S., Persic, I.S., Libra, M., 2012. Towards 50 years lifetime of
PV panels laminated with silicone gel technology. Sol. Energy 86 (10), 3103–3108.
[20] Reich, N.H., Alsema, E.A., van Sark, W.G.J.H.M., Turkenburg, W.C., Sinke, W.C.,
2011. Greenhouse gas emissions associated with photovoltaic electricity from
crystalline silicon modules under various energy supply options. Prog.
Photovoltaics: Res. Appl. 19, 603–613.
[21] Anctil, A., 2021. Comparing the carbon footprint of monocrystallinesilicon solar
modules manufactured in China and the United States. IEEE 48th Photovoltaic
Specialists Conf. (PVSC). https://doi.org/10.1109/PVSC43889.2021.9518632.
[22] Brandt B, Kletzer E, Pilz H, Hadzhiyska D, Seizov P. Silicon-Chemistry Carbon
Balance: An assessment of Greenhouse Gas Emissions and Reductions. 2012.
V. Poulek et al.