By now you’ve probably heard of the Boeing 787 Dreamliners and the problems they had in their first weeks in the air. Basically, the Dreamliner is an extremely fuel-efficient airliner. It was the first to use composite materials to reduce weight and the first to use “large format” lithium-ion batteries.
Due to fuel leaks and spontaneous fires in the batteries that exceeded the normal growing pains of any new, complex system, the entire fleet was grounded in mid January. Today, Chicago Tribune reports that the Federal Aviation Administration has permitted Boeing to perform a single “ferry flight” to relocate one of their planes so they can continue investigations. There is still no conclusion about the cause of the failures and FAA and National Transportation Safety Board officials don’t expect one for at least a couple months.
I wanted to better understand the problem so I asked Northeastern researchers K.M. Abraham and Pete Manolios for the takes on it all. Abraham is a research professor in the Northeastern University Center for Renewable Energy Technologies with 30 years of experience in the world of lithium batteries. He was quoted in two recent Wired articles about Boeing’s troubles, here and here. Manolios is an associate professor of computer and information science who has worked with Boeing and NASA for nearly a decade. The Dreamliner team commissioned Manolios to build an algorithm (dubbed CoBaSa) that can automatically integrate the various safety systems onboard the plane.
Abraham explained that lithium-ion batteries are such a hot topic (pun not intended) because they can store up to ten times more energy than traditional batteries. This is what makes them so energy efficient but it is also precisely why they carry potential safety hazards. It’s the difference between taking a match to a couple grains of gunpowder or a hand grenade full of the stuff.
Now imagine the gunpowder is in the same vessel as a lit match, and a polymer membrane about half the thickness of a human hair is the only thing separating the two. This is akin to the situation in a lithium-ion battery, where the membrane separates two chemical reagents that are highly reactive with one another. Any failures in the system could allow the two chemicals to come into contact (internally short circuit), which would mean certain death for the battery…and a big explosion.
Lithium-ion batteries are pervasive these days. They’re in our cell phones and our computers. They’re the sole power storage devices in all electric vehicles like the Nissan Leaf and Tesla Roadster. All told, Abraham said there are more than 10 billion lithium-ion batteries out there, powering our digital world one chemical reaction at a time. But that’s no reason to get into a tizzy, as my mom would say. The batteries in these devices have gone through extensive optimization steps over the years. The chance of a fire in any of them is about one in 10 million.
According to the press, the Dreamliner batteries were also manufactured according to accepted specifications. It could be, Abraham speculated, that the specifications relevant in the small-format batteries in our cell phones and electric cars simply aren’t enough at the larger scale.
The real problem may also have stemmed from how the batteries were used, said Manolios. “What seems to have happened is that there was a very large demand placed on the batteries and while they were charging they caught on fire,” he explained, pointing to a Time Magazine article on the topic.
While Manolios’ CoBaSa algorithm wasn’t designed to detect battery failures or fuel leaks, it’s possible that it could be used to prevent the former, he said. “We used my algorithm to synthesize software architectures, which involved figuring out which cabinets to place avionics code on, subject to a very large number of declarative constraints,” he said.
“It seems likely that we could use CoBaSa to express constraints saying that the power demands to the battery do not exceed a particular limit.” CoBaSa could then synthesize a system that doesn’t demand more power than the battery can provide, he explained.
Abraham is taking another approach, working on entirely new systems. He invented a battery called lithium-air, which uses oxygen from the atmosphere as the [cathode] and is significantly less hazardous than those described above. “It’s still in the early stages,” he said, “but there’s a worldwide effort in making it a practical battery.”
Ultimately, we’ll have to wait for the results of Boeing’s field tests to know exactly what happened. But I think it’s important we not put this down in the record books as a fundamental flaw in lithium battery technology. There are loads of researchers in the world, and several at Northeastern, all figuring out ways to make safe energy-efficiency a tangible goal.