New Life-Cycle Assessment Reveals Your Photovoltaic Mileage May Vary
by Jeremy Elton Jacquot, Los Angeles 
on 02. 9.08
Image courtesy of Wikimedia Commons
Not all photovoltaic technologies are created equal; some, in fact, incur quite heavy environmental footprints - producing silicon, for example, consumes a lot of water and energy while refining zinc produces a sizeable chunk of emissions. Environmental Science & Technology's Naomi Lubick reports that Vasilis Fthenakis, a scientist at Columbia University and the Brookhaven National Laboratory, just finished a LCA of some of the leading technologies which determined that new thin-film cadmium-telluride (CdTe) materials - such as the ones we covered here - come out on top.
Benefiting from its highly efficient energy conversion, CdTe photovoltaic systems consumed less energy and produced fewer emissions; in addition, when compared to its multicrystal and ribbon silicon competitors, the CdTe technology had the lowest cost. In order to obtain these results, Fthenakis and his colleagues compared data from more than a dozen solar companies, taking into account the manufacturing process, energy conversion and various components.
Unfortunately, the assessment failed to shed light on the technologies' total environmental impact - "not telling you exactly what your impact is if you were to buy them," as Corinne Reich-Weiser, a graduate student at UC Berkeley, explained. For instance, she notes that the emissions produced during the transportation of components before production and assembly are only partly taken into consideration; moreover, the assessment is based on idealized European and U.S. grids even though most components are built in China.
Still, it provides an effective means of "easily comparing" all of the available technologies, she says, deeming it "incredibly useful." New and future solar technologies should be able to bridge that emissions gap within the coming years as companies continue innovating and expanding their operations. Fthenakis notes that the one missing element from his assessment he hopes to amend soon is the end-of-life and recycling data; he believes this should help make the technologies' emissions profiles even better.
Via ::ES&T: New photovoltaics change solar costs (journal)
See also: ::Hairy Solar Panels Could Result From Nanowire Breakthrough, ::Inflatable Solar: Coolearth Concentrated Photovoltaics
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I like this post because even when we are using a clean energy source, there are emissions somewhere and LCA are important to look into. That is why we should continue to focus on efficiency and conservation because a kWhr saved is a kWhr not generated or something like that.
Don’t get me wrong, I love PVs, but what the post omits is the fact that Cadmium (Cd) is a highly toxic, cancer causing material that is 1 of 6 materials banned by the European Union’s Restriction of Hazardous Substances Directive. http://en.wikipedia.org/wiki/ROHS
The US can’t even use Cadmium in nano-meter thin films on its TANKS! Trust me on this. ;)
Seems like windturbines are more green?
@Mr. Brody: Cadmium plating is still widely used on a number of mil spec fasteners, so the gov't hasn't exactly given it up.
Speaking of Life Cycle Assessments
I've seen no coverage of these studies published in the Journal of Science, which allege that switchgrass may actually increase GHG emissions by 50% if you factor in emissions from land use.
http://www.grist.org/news/2008/02/08/biofu/index.html
The government has yet to give up on nuclear power, either.
@Scott
In future programs like the Army's FCS, NO CADMIUM will be used. They have to design for lead free solder also.
See page 7:
http://www.meggair.com/FCSWorkFlowDown.pdf
Sorry
So the most environmentally friendly power system is one that isn't commercially available? I haven't seen anything about these systems actually being used anywhere.
I also wonder about its efficiency. Your crystalline and polycrystalline cells usually get somewhere in the 12-14% efficiency range but I know the Ovonics thin film panels (we use them on our work trailer) get 8-10% efficiency. If the cdTe systems are along the same lines do they account for the much greater surface area needed to produce the same power and the increase in shipping emissions from ordering more spacial volume of panels (not necessarily weight since I don't know what their weight comparison is).
One other issue with solar installations --all the analyses about
KWh's generated and CO2 eliminated go out the window when a
PV installation under-perform, due to any factors, include neglect, mostly, improper siting & design, workmanship, etc.
I'd like to invite everyone to test our free PV performance benchmark website at --www.pvmonitor.net on it and give us a critique. I'll be happy to run an engineering assessment of any site's performance, if one can provide me with some actual performance numbers and date-times of these numbers. We are trying to refine it for ease of use and add more functionality.
We are focused on enhancing the practice of photovoltaics. Thanks for your interest and response.
Steve Yang, E.E. alias solarMD
scyang@wattminder.com