THE SECOND LIFE OF A 300 KW PV GENERATOR MANUFACTURED WITH RECYCLED WAFERS FROM
THE OLDEST GERMAN PV POWER PLANT
K. Wambach1, S. Schlenker1, A. Müller1, M. Klenk2, S. Wallat3, R. Kopecek4, E. Wefringhaus5
Deutsche Solar AG, Solar Material, Alfred-Lange-Str.18, D-09599 Freiberg Germany,
Tel. +49-3731301-3900, Fax: +49-3731-301-3910, email: firstname.lastname@example.org
Sunways AG, Macairestraße 3-5, D-78467 Konstanz, Germany, 3 Solarwatt AG, Maria-Reiche-Straße 8, D-01109 Dresden,
Germany, 4 University of Konstanz, Faculty of Sciences, Jakob-Burckhardt-Str. 27, 78464 Konstanz, Germany,
International Solar Energy Research Center Konstanz e. V. (ISC), Rudolf-Diesel-Str.15, 78467Konstanz, Germany
ABSTRACT: Within one year, SolarMaterial, a business unit of Deutsche Solar AG, and their co-operation partners have
recycled Germany’s oldest solar installation on the island Pellworm. By this means, modern cells and modules have been
created of 23 year old wafers. After the recycling of the end-of-life modules the recovered wafers are reprocessed by
Sunways AG in Konstanz. The cells were used for modules assembly at Solarwatt in Dresden. The co-operation project
proves that it is possible to recycle even very old products by modern standard processes in a value-conserving manner. The
cells and modules meet all quality standards of today’s photovoltaic products. There is nothing that prevents the modules
from having a long second life until their next recycling.
Keywords: Recycling, PV Module, Silicon
The oldest German PV-generator with 300 kWp
nominal power was installed in 1983 on Pellworm island
in the north of Germany (Figure 2) . It was already out
of operation for several years because of electrical
insulation defects (shutdown 1989). Most of the 17,568
pieces of AEG PQ20 double glass modules with noble
steel frames with an original cell efficiency of 8% were
still in an excellent condition (Figure 1) but several
defects were found ranging from isolation problems and
glass breakage to delamination. The 300kW PV generator
was removed from its wooden rack during summer/fall
2005 because the solar field was modernized with new
state of the art standard modules for future monitoring by
EON-Hanse AG. The old modules were delivered to the
recycling plant of Deutsche Solar AG in autumn 2005 Figure 2: PV generator on the German island Pellworm
By a thermal and chemical process a large amount of
wafers could be retrieved. First the laminate was burned 2 CELL PROCESSING
off to disunite the module compound structure.
Afterwards the recovered solar cells were treated in an Due to strong anisotropic etching during the first
etching line to remove the metallization, anti-reflecting solar cell process the wafer surface showed significant
coating and pn-junction subsequently. Instead of selling steps between the crystal grains up to 35 µm Figure 3.
the wafers on the market, Deutsche Solar AG in For this reason Laser edge isolation showed better results
cooperation with SolarWorld AG organised the compared to plasma etching. Special care had to be taken
reprocessing, module production and installation of the in the screen printing process to avoid grid interruptions .
new generator. The experiences of the thermal and Highly flexible printing sieves improved the results
chemical treatment are presented in . The subsequent notably.
part of the project the second lifetime from recovered
wafers to a new generator is described in the presented
paper. It was firstly possible to analyse the particularities
of the use of recycled wafers in conventional cell
processing and module production facilities.
Figure 1: Characteristic IV-curve of an old AEG PQ20 Figure 3: Step between crystal grains and cavities due to
Module from Pellworm island ultrasonic welding
The original ultrasonic welding process on the solar cells 3 MODULE ASSEMBLY
caused a change of the material properties of the wafer.
During the chemical treatment of solar cells for removal The company Solarwatt AG, situated in Dresden,
of the metallization holes were etched into the wafer at manufactured modern standard modules with 72 cells and
the welding positions. EDX measurements documented a power between 89 and 104 Wp (Figure 9) as a certified
that after the etching process the cavities were free of OEM-product of SolarWorld AG with full warranty.
metals (Figure 4, ,  ). Characteristic data of new modules are shown in figures
Figure 7 / Figure 8 and table 1. After cell encapsulation
an increase in efficiency up to 2% was obtained.
Figure 4: Metal free cavities after etching process
These cavities lower the yield of the emitter diffusion
and the screen printing process. Shunts and grid line
interruptions (Figure 5) could be observed frequently.
The wafers and cells with such defects were reused as
feedstock material. The average value of the cell
efficiency is 13.47%. As maximum cell efficiency 15.4%
was obtained. Figure 7: Distribution of Isc
Figure 5: Grid-line interruption
The Wacker Silso wafers used in the Pellworm modules
were cut with higher tolerances compared to state of the
art wafers. The length of the wafers varied by more than Figure 8: Distribution of Voc
1 mm. The angles frequently deviated from 90° (Figure
6). Reprogramming of the position system in the solar
cell line therefore was necessary. Somewhat higher
tolerances of the busbar positions and alignment could
not be avoided.
Figure 6: Stepped and inclined edges of solar cell
Figure 9: Distribution of power classes of the new
abiotic global warming ozone layer human photochem. acidification eutro-
depletion (GWP100) depletion toxicity oxidation phication
chemical treatment recycling glass recycling aluminium
thermal treatment avoidance of new wafers transport
Figure 10: Results of the LCA (CML baseline method 2000, characterisation)
and thermal treatment at the recycling plant of Deutsche
Solar a detailed Life Cycle Inventory (LCI) was made.
The LCI data is based on data collected during the
project as well as data from the Ecoinvent 2000 database.
For the evaluation of environmental impacts, the CML
baseline-2000 method was used. In Figure 10 result of
the LCA are shown. The chemical and thermal treatment
as well as the transport to the recycling plant leads to an
environmental burden (positive contribution). This
contribution is opposed to the environmental disburden
(negative contribution) due to the reuse of wafers, glass
and metals. The sum of negative and positive
contribution is scaled to 100%, because each category is
evaluated by a different indicator with its own unit.
For all impact categories the disburden due to the
reuse of wafers, metals and glass is higher than the
burden of the environment due to the recycling process
itself. That is due to the environmental impact of glass
Figure 11: Module assembly at Solarwatt and metal production as well as impact related to wafer
production is credited to the impacts of the recycling
Original New module The impact of the transport of the modules with three
Pellworm module lorries to Freiberg is too small to be visible in the figure.
Module power 17.1± 10% 89 - 104±5 % Its relative contribution amounts between 0,5 and 2 %.
Cells per module 20 72 5 SUMMARY AND RESULTS
Type of silicon multi-Si multi-Si
cells The project displayed:
Cell dimension 100x100x0.4 100x100x0.4 – The old silicon wafers are still of excellent quality.
[mm] That proves the excellent long time stability of
Module 460x560 1282x644 crystalline solar silicon
dimension [mm] – The recycled wafers can be reprocessed to cells
achieving state of the art cell efficiencies in good
Table 1: Comparison of technical data of the original and yield for a speciality market. This is an important
new modules result for replacement of defective modules e.g. in
PV building integration. Even old cell types can be
4 LIFE CYCLE ASSESMENT available allowing repair of such generators.
– Modules can be manufactured with recycled materials
and reinstalled in systems as a full quality product
The recycling of the Pellworm modules was
with today’s technology good for another 25 – 30
evaluated concerning its environmental effects. A Life
Cycle Assessment (LCA) can give information about the
environmental impacts of the recycling process and the
reuse of recovered wafers and materials. For the chemical
Figure 12: Comparison of results of sun-simulator
measurements of an original modules and a module with
 K. Maaß, „40 Jahre Solartechnologie aus We-
del in der Raumfahrt und auf der Erde“, Klima-
schutzfonds Wedel e.V., Heydorn Druckerei &
Verlag, Uetersen 2005 p.38f.
 J. Siemer, „Neues Leben für ein altes Kraft-
werk“, Photon, November 2005, p. 86 – 88
 E. Bombach, I. Röver, A. Müller, S.Schlenker,
K. Wambach, R. Kopecek, E. Wefringhaus,
“Technical Experience During Thermal And
Chemical Recycling Of A 23 Year Old PV-
Generator Formerly Installed on Pellworm Is-
land”, 21th European Photovoltaic Solar Energy
Conference, September 2006
 Forum für Zukunftsenergien e.V., Godesberger
Allee 90, D-53175 Bonn „Energieversorgung
mit erneuerbaren Energien am Beispiel der
Nordseeinsel Pellworm, Ein lokaler Entwick-
lungsplan“, Contract no. 4.1030/Z/95-147
 E. Wefringhaus, „Zwischenbericht Pellworm
Wafer“, internal communication, Konstanz
 R. Kopecek, „Charakterisierung und Solarzel-
len aus recyceltem Material der Deutschen So-
lar AG“, internal communication, Konstanz
Special thanks are given to our cooperation partners
from Eon Hanse AG; University of Utrecht, SolarWorld
AG and Solarnova who made this work possible with
their kind cooperation.