Hundreds of thousands of tons of lead, a heavy metal that can damage the brain and kidneys, is found in the lead-acid batteries used in nearly half the vehicles in the world. Currently as much as 98 percent of all battery lead is recycled, however this may not always be the case. New battery technologies, including lithium-ion batteries, are threatening to replace lead-acid batteries in new vehicles, which could break the relatively sustainable recycling loop.
With this in mind, a newly-harnessed material called perovskite and a new system proposed by MIT researchers proposes a potential use for lead from car batteries that would otherwise be discarded: use it to build solar panels. The system is based on the recent development of solar cells using crystalline structures called perovskite, a material discovered to be useful for manufacturing solar cells back in 2009. Made up mostly of calcium titanate, perovskite is found in deposits all over the world.
Currently less efficient perovskite derivations, meant to reduce the environmental hazards related to the lead variation, use other elements such as tin. However the method of using lead from used car batteries to make solar cells could prove environmentally friendly as it would prevent lead from being discarded dumps and other hazardous sites.
“Once the battery technology evolves, over 200 million lead-acid batteries will potentially be retired in the United States, and that could cause a lot of environmental issues,” said Angela M. Belcher, co-author of the paper which was published in the journal Energy and Environmental Science.
According to Belcher, the lead perovskite photovoltaic cells have achieved power-conversion efficiency of more than 19 percent, which is close to that of many commercial silicon-based solar cells. However, the really exciting thing is how much easier and potentially cheaper the process of making solar cells from perovskite is, as it doesn’t require the same high temperatures or specialized equipment. The researchers even made a demonstration video for those interested in watching the step-by-step process of used-battery-to-solar-cell-conversion unfold.
Once the solution is made it can be used as a thin flexible film with half-micrometer thick perovskite cells. The researchers estimate that since the material is so thin a single car battery could produce enough solar panels to provide electricity to 30 households. In the finished solar panels the layer containing lead would be fully encapsulated by other materials, limiting the risk of environmental contamination. Once the panels run through their lifecycle the material can be recycled into new panels. Although with solar panel technology accelerating at breakneck speeds, it’s hard to know what panels will be made of 20 or 30 years down the road.
“This paper is about the excitement in the field of these perovskite materials and thinking about the environmental implications of extracting lead,” Belcher said. “The beauty is that this new process is pretty interchangeable with the current production method.”
Another course that perovskite solar cells could take is a spray-on solar cell, as was recently developed by researchers at the University of Sheffield. The spray is only 11 percent efficient, but it is cheap to make and could benefit from economies of scale in large-scale panel production that could combine to considerably cut the price per watt figure.
“I believe that new thin-film photovoltaic technologies are going to have an important role to play in driving the uptake of solar-energy, and that perovskite based cells are emerging as likely thin-film candidates,” said Prof. David Lidzey, one of the researchers who helped develop the spray-on technique.