

Old car batteries could make cheaper, more efficient solar panels - nkzednan
http://www.washingtonpost.com/news/speaking-of-science/wp/2014/08/18/old-car-batteries-could-make-cheaper-more-efficient-solar-panels/

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gjm11
To rephrase the story a little: Instead of making solar panels out of silicon,
with 20-25% efficiency, we could make them out of perovskite, which contains
lead and yields a little below 20% efficiency. Because then we could reuse
lead from car batteries instead of putting them in landfill.

It seems to me that by the time the car batteries are in the recycling system,
ready for use to make perovskite solar panels, the lead-pollution problem is
already solved. So then the question is: You have a stash of car batteries
that you can reuse if you want to. Do you want to make solar panels out of
silicon or out of perovskite?

It looks to me as if the answer is clearly "silicon". Can it really be harder
to dispose of the lead batteries safely than it is to make perovskite solar
panels out of them?

It had better not be, given that the amount of lead needed by one solar panel
installation is about 1/30 the amount in one car battery. There are a _lot_
more car batteries made per year than 1/30 the number of solar panel
installations.

~~~
cowsandmilk
um, it is not easy to dispose of lead batteries "safely". In fact, there is no
method currently to do so. Do you have a suggestion for how to do so?

There's a reason it is illegal in most (all?) states to throw out a car
battery[1]. Currently, over 98% of battery lead is recycled into new
batteries[2]. This is about affording us the flexibility to put battery lead
to other uses while still having it be largely recoverable.

As for silicon vs. perovskite, did you miss the fact that a solar cell should
be able to have both and show higher output than silicon alone?

[1]
[http://c.ymcdn.com/sites/batterycouncil.org/resource/resmgr/...](http://c.ymcdn.com/sites/batterycouncil.org/resource/resmgr/Lead_Acid_Info/StateLeadAcidBatteryLawsPoin.pdf)
[2]
[http://batterycouncil.org/?page=Battery_Recycling](http://batterycouncil.org/?page=Battery_Recycling)

------
bequanna
'Instead of adding more lead to the environment, this process would actually
prevent lead in defunct car batteries from entering landfills.'

As I understand it, batteries are voluntarily recycled. By changing what the
batteries are recycled into, how is this preventing those who currently throw
used batteries in a dumpster from continuing that practice?

We've done a good job recognizing the health threat lead in our environment
poses and actively working to reducing levels.

Given that there isn't really any safe amount of lead exposure, maybe it is
just more prudent to permanently transition away from using lead in all
products where feasible.

Lead Blood 'Levels of Concern' over time:
[http://www.lead.org.au/lanv14n1/lead_s18.gif](http://www.lead.org.au/lanv14n1/lead_s18.gif)

~~~
tim333
>Instead of adding more lead to the environment

Of course the number of lead atoms on earth is pretty much constant and they
are out there in the environment somewhere. The idea is to have them somewhere
harmless rather in us. Leaded fuel was a bit of a disaster from that point of
view hence the decline in the graph as leaded fuel was banned. (Still
available in Algeria, Iraq, Yemen, Myanmar, North Korea according to
Wikipedia). I think the solar panels could be done without net lead ending up
in people if handled properly. Incidentally there's a probably a fair bit of
lead a few mm from you in the solder of your electronic gadget but it doesn't
do any harm there as it's had to get it from solder in to people. Hopefully
the panels would have similar stability and not be like lead based paints
which are a problem.

There are some similar question marks with cadmium based solar panels of which
First Solar have installed 8GW worth. I think I might worry slightly about
those too, probably more that lead. Indeed I think First Solar have only done
industrial installations for power companies rather than domestic so the
recycling can be done properly.

~~~
wycx
Actually, the number of lead atoms is not constant. It is steadily increasing,
due to U and Th decay.

------
maho
The researchers synthesize 21 kg of PbI2 out of a single battery. PbI2 has a
density of around 6 g/cm^3. The solar cells have a 500nm coat of PbI2. If I do
the math, then I get 7000 m^2 of solar panels out of it [1], which is 10x more
than what they claim. How can this be?

In the paper [2], on the bottom of page 4, they give the answer to this
discrepancy:

"By considering the structure of PSCs (~500 nm-thick PbI2 coating) and the
material loss during the spin-coating process (~89.6%), 21.5 kg of PbI2
enables the fabrication of ~709.0 m2 PSCs."

This seems ridiculous. If you use 21 kg of material for spin coating, 19 kg
don't just vanish into thin air. I would imagine that the material that is
flung off can be collected in the bottom (or somewhere else). But maybe that
is not possible?

If 90% of the material would disappear during spin-coating, then how can the
researches claim that they safely recycle lead? They are doing the exact
opposite!

[1]
[https://www.google.com/search?q=21+kg+%2F+(6+g%2F(cm^3))%2F(...](https://www.google.com/search?q=21+kg+%2F+\(6+g%2F\(cm^3\)\)%2F\(500+nm\))

[2]
[http://pubs.rsc.org/en/Content/ArticleLanding/2014/EE/C4EE00...](http://pubs.rsc.org/en/Content/ArticleLanding/2014/EE/C4EE00965G)

~~~
akiselev
From a quick search [1] it looks like the process for spin coating PbI2 is a
bit more involved than just spinning a substrate. There are several other
solvents an a boiling process which will have byproducts but ones that have
their own recycling process.

[1]
[http://www.rsc.org/suppdata/ra/c3/c3ra43228a/c3ra43228a.pdf](http://www.rsc.org/suppdata/ra/c3/c3ra43228a/c3ra43228a.pdf)

------
raverbashing
Lead batteries are not going away. Modern batteries don't have a lot of the
advantages that they have (cost, float charging, starting current, etc)

The batteries are sealed, it's not like they're being expelled in the exhaust
like in Tetraethyllead or being in close contact with people.

Sure it's better to recycle them or dispose of them properly rather than
throwing in a landfill, but let's stop the knee-jerk reaction "lead == bad"

~~~
frenchman_in_ny
Yes, sealed AGM lead batteries have certain advantages over other batteries,
however I take issue with "it's better to recycle them or dispose of them
properly rather than throwing in a landfill, but let's stop the knee-jerk
reaction 'lead == bad'"

More often than not, the US (as a whole) simply exports the problem to other
countries with weaker regulation, recycles there, and imports the finished
goods after.

[0] [http://ehp.niehs.nih.gov/wp-
content/uploads/117/10/ehp.09006...](http://ehp.niehs.nih.gov/wp-
content/uploads/117/10/ehp.0900696.pdf)

[1]
[http://www.tandfonline.com/doi/pdf/10.1080/15459624.2011.601...](http://www.tandfonline.com/doi/pdf/10.1080/15459624.2011.601710)

[2] [http://www.nytimes.com/2011/12/09/science/earth/recycled-
bat...](http://www.nytimes.com/2011/12/09/science/earth/recycled-battery-lead-
puts-mexicans-in-danger.html?pagewanted=all&_r=0)

------
maho
Original MIT press release: [http://newsoffice.mit.edu/2014/recycling-
batteries-into-sola...](http://newsoffice.mit.edu/2014/recycling-batteries-
into-solar-cells-0818)

Paper (non free, unfortunately):
[http://pubs.rsc.org/en/Content/ArticleLanding/2014/EE/C4EE00...](http://pubs.rsc.org/en/Content/ArticleLanding/2014/EE/C4EE00965G#!divAbstract)

As far as I understand it (I am not a chemist), the video only shows the
production of perovskite crystals. The paper goes into more details on the
fabrictation process of actual solar cells:

\- Patterning the FTO coated glass (glass with a transparent, conductive
layer; you can buy this commercially) using photolithography.

\- Depositing a 500nm thick layer of 20 nm TiO2 nanoparticles

\- Depositing the perovskite (this is what is shown in the video)

\- Depositing a 50nm gold layer

------
ErikRogneby
Lead is certainly a lot more common than the Indium used in high efficiency
silicon panels.

------
mikexstudios
A disadvantage of perovskite solar cells is that they degrade quickly upon
contact with moisture. So they need to be encapsulated very well.

