Old car batteries could make cheaper, more efficient solar panels | Hacker News Reader

Old car batteries could make cheaper, more efficient solar panels

washingtonpost.com

75 pointsnkzednan19 comments

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.

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/... [2] http://batterycouncil.org/?page=Battery_Recycling

Where are you seeing 20-25% effi PV modules? The physics of silicon's bandgap prevents getting much above 18% without (expensive) multiple junction layers (of different material) or concentrators, which tend to reduce module lifecycle time.

My guess is that as lead acid car batteries are phased out, then the lead acid recycling industry will migrate to supplying stationary batteries. By that I mean e.g. residential photovoltaics storage, grid load smoothing, battery banks for rapid charging electric cars. Situations where the weight/bulk doesn't matter, but low cost does matter.

If there are no other economic uses for the lead then those applications should become nice and cheap. However this is just the opinion of an armchair energy wonk, so take it with a big grain of salt.

I think the underlying assumption here is that there is a problem with lead recycling. AFAIK, nearly all lead batteries are recycled.

We are many, many years from the inflection point where electric cars will start displacing internal combustion.

'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

I agree that the argument about keeping lead out of the environment is weak. As for using lead in any products I think it comes down to whether its possible that the lead leaks out into the environment in any way. That is very unlikely with car batteries (assuming they are recycled correctly) and remains to be shown for these solar panels. If the lead in them is bound in a way that makes it impossible to leak out (despite being exposed to weather or broken in a storm etc) I think it's a fair tradeoff.

That's a pretty suggestive graph. If you look a bit more closely you'll see the opposite of what it suggests, we're halfway into the third decade without change in 'level of concern'. That doesn't mean there even is a safe level, it does seem to mean that we are definitely not approaching '0' by 2020.

>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.

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

Its the usual argument for green products "ours produces 25% less blah". Doesn't stop the existing products being on the market, in fact it often looks like more products so likely more environmental damage.

No.

Many people want cars to stop using lead acid batteries, not due to concern about the lead, but because technology has advanced and there are better materials.

If this occurs, then the recycling stream will stop as there is now nowhere to reuse the lead. This is an option for a new way to reuse the lead.

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(...

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

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

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"

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...

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

[2] http://www.nytimes.com/2011/12/09/science/earth/recycled-bat...

Original MIT press release: http://newsoffice.mit.edu/2014/recycling-batteries-into-sola...

Paper (non free, unfortunately): http://pubs.rsc.org/en/Content/ArticleLanding/2014/EE/C4EE00...

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

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

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

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