MIT team proposes process to recycle lead-acid batteries to fabricate solar cells
18 August 2014
Researchers at MIT have devised an environmentally-responsible process to recycle materials from discarded automotive lead-acid batteries to fabricate efficient organolead halide perovskite solar cells (PSCs)—a promising new large-scale and cost-competitive photovoltaic technology. The process simultaneously avoids the disposal of toxic battery materials and provide alternative, readily-available lead sources for PSCs.
The system is described in a paper in the RSC journal Energy and Environmental Science, co-authored by professors Angela M. Belcher and Paula T. Hammond, graduate student Po-Yen Chen, and three others.
Perovskite films, assembled using materials sourced from either recycled battery materials or high-purity commercial reagents, show the same material characterizations (i.e., crystallinity, morphology, optical absorption, and photoluminescence property) and the identical photovoltaic performance (i.e., photovoltaic parameters and resistances of electron recombination), indicating the practical feasibility of recycling car batteries for lead-based PSCs.
—Chen et al.
PSC technology has advanced rapidly from initial experiments to a point where its efficiency is nearly competitive with that of other types of solar cells. The power conversion efficiencies reached over 15% within 18 months of development; perovskite-based photovoltaic cells have now achieved power-conversion efficiency of more than 16%—approaching that of many commercial silicon-based solar cells. Accordingly, interest in the technology in the research community has soared.
(C&EN quoted University of Oxford physicist Henry J. Snaith as saying “It seems we’ve all been bitten by the perovskite bug.”)
However, the researchers note, the manufacture of PSCs raises environmental concerns regarding the over-production of raw lead ore, which has harmful health and ecological effects. Using recycled lead from old car batteries can alter the environmental impact.
Because the perovskite photovoltaic material takes the form of a thin film just half a micrometer thick, the team’s analysis shows that the lead from a single car battery could produce enough solar panels to provide power for 30 households.
As an added advantage, the production of perovskite solar cells is a relatively simple and benign process. “It has the advantage of being a low-temperature process, and the number of steps is reduced” compared with the manufacture of conventional solar cells, Belcher says.
Belcher says that currently, 90% of the lead recovered from the recycling of old batteries is used to produce new batteries, but over time the market for new lead-acid batteries is likely to decline, potentially leaving a large stockpile of lead with no obvious application.
In a finished solar panel, the lead-containing layer would be fully encapsulated by other materials, as many solar panels are today, limiting the risk of lead contamination of the environment. When the panels are eventually retired, the lead can simply be recycled into new solar panels.
Belcher believes that the recycled perovskite solar cells will be embraced by other photovoltaics researchers, who can now fine-tune the technology for maximum efficiency. The team’s work clearly demonstrates that lead recovered from old batteries is just as good for the production of perovskite solar cells as freshly produced metal.
Some companies are already gearing up for commercial production of perovskite photovoltaic panels, which could otherwise require new sources of lead. Since this could expose miners and smelters to toxic fumes, the introduction of recycling instead could provide immediate benefits, the team says.
The work, which also included research scientist Jifa Qi, graduate student Matthew Klug and postdoc Xiangnan Dang, was supported by Italian energy company Eni through the MIT Energy Initiative.
Resources
Po-Yen Chen, Jifa Qi, Matthew T. Klug, Xiangnan Dang, Paula T. Hammond and Angela Belcher (2014) “Environmentally-responsible fabrication of efficient perovskite solar cells from recycled car batteries” Energy Environ. Sci., doi: 10.1039/C4EE00965G
Hui-Seon Kim, Sang Hyuk Im, and Nam-Gyu Park (2014) “Organolead Halide Perovskite: New Horizons in Solar Cell Research” The Journal of Physical Chemistry C 118 (11), 5615-5625 doi: 10.1021/jp409025w
If these perovskite cells are cheap enough clearly we are into a different ball game.
Even the worst areas in the continental US get around 30% off maximum solar insolation in the winter, unlike in Germany and the UK:
http://www.gaisma.com/en/location/brunswick-maine.html
Here is an indication of the size of the solar resource in residential and commercial building rooftops in the US:
http://www.nrel.gov/docs/fy09osti/44073.pdf
It is an old study, but the size of the rooftops available is not going to change much.
The 20% efficiency of these cells puts them on the top curve for the resource size.
The bottom line would seem to be somewhere in the region of 600-1,000GW nominal available in these locations.
Knocking that back a bit to allow for not using the lot and taking out for night times etc then there might be in the region of 150GWe available, disproportionately in the summer of course, but that is when load is highest, and I previously calculated that around 250GW nominal would be needed just to cover the excess of summer load over peak winter.
The viability of an energy source depends on its cost, and this is starting to look interesting everywhere in the continental US.
Posted by: Davemart | 18 August 2014 at 11:54 AM
Here is why they might be very cheap.
They might be able to be sprayed on, and the materials aren't expensive:
http://phys.org/news/2014-08-scientists-spray-on-solar-cells.html
Posted by: Davemart | 18 August 2014 at 11:55 AM
There's a logical disconnect in the article itself. It presumes that recycled lead incurs none of the environmental costs of lead mining. So long as the total amount of lead in the inventory of batteries (not just for automobiles but scooters, UPSs and such) continues to go up, this assumption is false.
Posted by: Engineer-Poet | 19 August 2014 at 09:55 AM
@EP:
I'm no fan of lead anywhere in the environment myself as unlike radiation it really does seem to to damage at any level no matter how low.
However there is no logical disconnect in the article, you just missed it.
Their argument is that lead batteries in cars will get gradually displaced, presumably by the much lighter lithium and in my view in combination with capacitors, so that the lead currently used in batteries is free for solar panels without further mining.
At 30 houses worth, presumably around 150kw nominal, of panels per car since there are more cars than houses that is plenty enough for the job without any increase in the lead inventory, and they argue it will be better locked away.
I'm not keen myself on it though, and wonder if there are alternatives to lead.
Posted by: Davemart | 19 August 2014 at 10:58 AM
So long as the perovskite panels are being made while PBSO4 battery inventories are still rising, there's no net environmental benefit. It's also questionable whether the widespread distribution of lead in panels is better than batteries and other concentrated forms for ultimate disposal.
I think the same questions should be asked about CdTe.
Posted by: Engineer-Poet | 19 August 2014 at 11:16 AM
Fair enough.
That is their argument though, they did not simply miss the point.
At least lead is abundant, which is another strike I had against CdTe.
Posted by: Davemart | 19 August 2014 at 01:21 PM
It looks as though others have thought of the lead problem:
'The performance of solar cell newcomer materials called perovskites has soared in recent months. But they still have big problems when it comes to working in real-world settings. For starters, the best perovskites contain lead, which is highly toxic. Now, two independent research groups report making solar cells with lead-free perovskites. So far, the new devices convert only about 6% of the energy in sunlight to electricity, less than one-third as much as lead-containing versions do. But that’s about how efficient leaded devices were only 3 years ago. So if the lead-free versions improve as quickly as their leaded cousins did, it could help propel perovskites into the marketplace.
Perovskites are a broad class of crystalline minerals that have been known for well over a century. But their ability to convert solar energy to electricity came to light only in 2009. Since then, the efficiency of perovskite solar cells has climbed from 3.8% to 19.3%, a pace of improvement unmatched by any other solar technology. By comparison, crystalline silicon solar cells, the leading commercial technology, convert about 25% of solar energy to electricity.
But lead could be a perovskite killer. In large part, that’s because the compounds are saltlike minerals that readily dissolve in water or even humid air. And the prospect of dissolved lead dripping onto the rooftops of homeowners with solar panels isn’t a pleasant one to companies looking to commercialize the technology.
The new reports could offer the beginnings of a solution. Both groups of researchers take a similar approach, replacing lead in the complex crystalline structure with tin, a metal that sits just above lead in the periodic table and thus shares a similar electronic structure. In a paper posted online on 1 May in Energy & Environmental Science, Henry Snaith, a physicist at the University of Oxford in the United Kingdom, and colleagues report making tin perovskite solar cells that achieve a maximum efficiency of 6.4%. And in an article posted today in Nature Photonics, Robert Chang, a materials scientist at Northwestern University in Evanston, Illinois, and colleagues report similar solar cells with efficiencies up to 5.73%.'
http://news.sciencemag.org/chemistry/2014/05/perovskite-solar-cells-get-lead-out
Gimme that tin! Much nicer!
Posted by: Davemart | 19 August 2014 at 01:26 PM
Durability is a problem too:
'As with organic solar cells, their long term stability is also highly questionable and they are particularly sensitive to moisture – a few drops of water can completely destroy the material.
So building a perovskite solar panel module capable of surviving for decades outdoors is most likely still some way off – in fact there’s no guarantee it’s even possible.'
http://www.businessspectator.com.au/article/2014/8/19/solar-energy/revolutionary-perovskite-solar-cells-could-be-game-changer-questions
Posted by: Davemart | 19 August 2014 at 01:35 PM