INTRODUCTORY SPECIAL INTRODUCTORY ... - PHOTON Info

Ask the Editors
Whether it’s about fi nancing, technology, or individual components:
PHOTON’s editorial staff answer question about every aspect of PV in its editorial offi ce hours.
Radioactive modules?
?
Since ruthenium is used as a dye in
pigment-based solar cells, can you
give me conclusive proof that, even if
the material undergoes extreme stress
due to module breaking, disintegrating,
or splintering, no radioactivity will be
released into the environment?
Jan Teckelmann,
by email
!
Pigment-based solar cells use a red
compound containing the metal ruthenium
(Ru) to absorb a specifi c portion
of the sunlight’s wavelength. »Naturally
occurring isotopes of ruthenium
are not radioactive,« explains Nils Metzler-Nolte,
who holds the chair of Inorganic
Chemistry at the Ruhr University
in Bochum, Germany, »so normal pigment-based
solar cells containing ru-
When does it pay to buy thin-film
panels?
? I’ve heard that thin fi lm modules are,
on average, one-third cheaper than
polycrystalline modules, but also only
produce half the power. Is that true?
Klaus Wäring,
by e-mail
! There is really no generic answer to
this question, since local irradiation
conditions must be taken into consideration.
According to PHOTON’s module
price comparison, the average price for
thin-fi lm modules was roughly 20 percent
less than the price for polycrystalline
modules at the beginning of July. At
the beginning of October, the difference
was around 15 percent.
Correspondingly, the effi ciency of
thin-fi lm modules is generally lower
than that of polycrystalline modules,
which have effi ciencies of around 14
percent. The effi ciency of cadmium telluride
(CdTe) and copper-indium-diselenide
(CIS) modules is around 10 percent,
compared to 7 to 8 percent for amorphous
microcrystalline silicon modules.
Panels using amorphous microcrystalline
modules would produce 33 to 50
percent less power per m2 of module
Not a source of radiation: pigment-based solar cells using red dye
containing ruthenium
thenium compounds cannot discharge
radioactive ruthenium.« Fuel elements
from nuclear reactors do contain small
amounts of radioactive ruthenium iso-
An array consisting of crystalline silicon modules
(left), and one with thin-fi lm modules (right). Whereas
the power yield per nominal W is quite similar for both
technologies, thin-fi lm panels’ output per m2 of module
surface is much lower.
surface space than crystalline modules.
But a panel’s effi ciency does not really
tell you how much power you will get per
rated W. Nominal output is measured
under standard test conditions (STC),
topes, but that doesn’t mean
the element itself is always
radioactive. Metzler-Nolte
says there’s no greater risk
of toxicity with these compounds
than with alternative
dyes that don’t contain
metal. As a general rule, if a
dye module containing ruthenium
breaks, you should
handle the debris with care
– but that’s true of all solar
modules. Apart from that, ruthenium
is indispensable in
pigment-based solar cells for
technical reasons. »There’s
currently no substitute dye
that works as well, but we’re still working
on it,« says Henning Brandt, a researcher
at the Fraunhofer Institute for
Solar Energy Systems. djs, ste
which is 1,000 W of irradiation per m 2 .
Thus this measurement only takes one
possible set of conditions into account.
It fails to demonstrate whether the panel’s
performance differs under other solar
conditions.
The results of PHOTON’s fi rst fi eld
test showed that CIS and CdTe modules
surpassed their crystalline competitors
when solar irradiation was between 45
and 80 percent of STC. Above or below
STC, polycrystalline modules perform
better. Nonethelsee, depending on how
prevalent certain solar conditions are at
a given location, thin-fi lm modules can
actually certainly outperform polycrystalline
modules. According to PHOTON’s
test, a polycrystalline and a monocrystalline
module came in fi rst and second
place in terms of power production for
measurements taken throughout 2008.
They were followed by a thin-fi lm panel,
manufactured by First Solar Inc., which
came in third. nw
November 2009 109
Roberto Mettifogo / photon-pictures.com
Greatcell Solar SA
Our editorial offi ce hours is a service for subscribers.
Do you have questions about an article, or general questions
about PV? Our experts can be reached every friday
between 9 and 12 by phone at 415/509-5296.
Please have your customer number available
(it’s located on the magazine address label).
We will answer any questions per email, letter, or fax upon
receipt – include the keyword editorial offi ce hours
Industry Industry Registry Classifieds Job Opportunities Ask As the Editors Internships Education Education Educatio Educatio & Training Events Statistics Test Lab