With the root cause of the Boeing 787 battery fire still unclear, one leading battery expert suggested this week that the need for an active cooling system on Dreamliners is even more important.
"This is a step in the right direction," Elton Cairns, a professor of chemical and biomolecular engineering at the University of California Berkeley, said of Boeing’s reported intention to put more space between the battery’s cells. "But it’s not clear that it’s sufficient."
Cairns told Design News that an active cooling system -- particularly one that uses a liquid coolant to draw heat away from the battery pack -- is especially important, given the fact that the failure mechanism in the JAL Boeing 787 fire in January is not fully understood yet. A liquid cooling system -- like the kind used in the Chevy Volt battery pack -- would be more likely to isolate heat and prevent it from passing from cell to cell, he said.
"The battery did catch fire and you don’t want that to happen under any circumstances," Cairns said of the 787 incident. "We know for sure that the thermal management system needs to be changed, even if there was an externally caused short circuit."
Cairns is a well-known expert in the battery community, having designed fuel cells for the Gemini space program, and having served at General Electric Research Laboratory, General Motors Research Laboratory, Argonne National Laboratory, and Lawrence Berkeley National Laboratory.
Click on the image below for a close-up look of the Dreamliner and some of the problems that have plagued it.
Boeing began assessing the idea for a "middle-of-the-market" airplane in 2002. (Source: Boeing Co.)
According to numerous news reports, Boeing plans to fix its 787 battery by employing additional spacing between the battery’s eight cells to allow for more effective cooling. Boeing reportedly will also use a more fire-resistant container, add sensors for monitoring cell temperatures, and equip the 787 with the ability to vent smoke to the outside. Venting would require that Boeing cut and reinforce holes in the jet’s carbon fiber skin, according to a report in The Wall Street Journal.
After more than a month of intense study of the January battery fire, Boeing is confident that its engineers know the way to fix the faulty lithium-ion battery packs that grounded the 787 Dreamliner fleet in January. The company is now awaiting approval from the Federal Aviation Administration (FAA) to test the new battery design. “Ever since the fleet was grounded, our team has been working around the clock,” Boeing Co. spokesman Marc Birtel told Design News. "We brought in experts from outside, as well as within the company, to validate our ideas, and that culminated in our proposal to the FAA."
If the FAA approves the fix, Boeing would still have to demonstrate, through lab tests and flight tests, that the repairs are satisfactory. Afterwards, the aircraft could return to service. Still, approval may not be a slam dunk. Transportation Secretary Ray LaHood has said he wants to personally conduct a thorough review of the 787 battery situation. Satisfying LaHood would be critical, since the US Department of Transportation oversees the FAA.
The incident that provoked the grounding of the 787s occurred on January 7, 2013, at Boston’s Logan Airport. While the aircraft was parked at a gate, a mechanic found smoke and flames coming from the lithium-ion auxiliary power unit battery located in the aft electronic equipment bay. One firefighter sustained a minor injury while dousing the blaze.
Since that time, the National Transportation Safety Board (NTSB) has not found the root cause of the fire. In February, investigators determined that data from the flight recorder, combined with thermal and mechanical damage, pointed to short circuiting in one of the battery’s eight cells, leading to a thermal runaway condition. Temperatures inside the battery case were believed to have exceeded 500F. As of a March 7 press conference, however, NTSB had still not nailed down the cause of the short circuiting.
Cairns told Design News that the biggest safety concern is the low density of air at high altitudes. There, he said, it might be more difficult to draw heat away from the battery.
"A much safer solution would be to have a liquid-based thermal management system," he said. "You don’t want the battery to get too cold and you don’t want it to get too hot." A liquid-based cooling system would not be affected by the density of the surrounding air, he added.
Birtel of Boeing told Design News that the company will provide more details about the fix if it is approved by the FAA. For now, he said, Boeing is working with GS Yuasa Corp., manufacturer of the lithium-ion battery, to implement the improvements. "We see this as a permanent fix and the best fix for the airplane," Birtel told us.
"wouldn't hesitate to fly on an airplane that had this battery in it."
@Robortnorcross: Even I wouldn't hesitate to do the same but don't you think it's a bit risky? Also does these things (this one specially) got updates?
"Transportation Secretary Ray LaHood has said he wants to personally conduct a thorough review of the 787 battery situation. Satisfying LaHood would be critical, since the US Department of Transportation oversees the FAA.
I wouldn't hesitate to fly on an airplane that had this battery in it. After all after Ray La Hood (a career politician) who knows everything about engineering aircraft systems, batteries, etc. is finished with his "review" everything will be fixed. Too bad that he didn't fix the Toyota acceleration problem-- Oh wait he DID.
May be we can get the Navy Admiral who thinks global warming is his biggest problem he has to work with La Hood.
Clearly the cause of over heating needs to be discovered and solved. I' m sure that there are solutions that exsist. I did run across a project where a system was submerged in 3M™ Fluorinert™ Electronic Liquid. What are your thoughts on it or similar products heat transfer and fire suppression abilities?
I'm sure that I read somewhere earlier that the 787 requires two of these new style batteries at approximately 65 pounds each. I think the same article indicated that equivalent batteries of an already proven design type would weigh 20 to 25 pounds more. Since I work in aerospace, I understand the importance and desire to cut weight, but it woud seem that for approximately 50 pounds in weight savings there should be other alternatives. NiCad has been used for years in aircraft without the same risk level as NiMh. Since this is a totally new design aircraft, I would have to think that it includes all the latest levels of EMI sheilding and protection. Since the FAA is re-evaluating the use of on-board electronic devices, maybe Boeing could work with the FAA a bit to get the use of electronic devices approved in the 787 and then they could do away with things like the hundreds of copies of newspapers that get carried on board evey flight. That alone would probably make up for any weight penalty imposed by using proven battery technology, would probably help to improve consumer confidence in the safety of the aircraft and should helpt to get the program back in the air again.
The theoretical upper stability limit of water, above which oxygen should evolve, is 1.23 V and is also pH-dependent. Li-Ion battery works at higher voltage.
The triggering mechanism that induces thermal runaway is directly related to the extent of the cathode thermal instability, and increased oxygen generation Heat generation from the cathode is 3 - 4 times greater than from the graphite anodes at fully charged states because of oxygen that evolves from the cathode lattice above 200 deg C.
I don't think that aqueous cooling will be used to cool direct the electrodes, but there are non-aqueous liquides able to replace the water.
Possibility to implement water in electrode cooling <1%... the risk is to high for this type of Li-Ion battery
But isn't that the key point, Charles? Any peak temperature the battery hit during the combustion is not relevant; once thermal runaway starts, the cell heats itself. The key point is, was the cell running at a temperature high enough to start the thermal runaway, before it got started, and due to some external load or charge condition, such that a cooling system could have kept the cell temperature below the ignition point. If so, some cooling system enhancement is needed. If not, it would not be.
My understanding, which may be wrong, is that once thermal runaway starts, no external cooling will help, the cell just flames itself.
I suspect that the respondents here who are dumping on Boeing are barking up the wrong tree. I think enough testing was done to assure that operation and charging never drove the cells anywhere near the temperature thermal runaway point. This would make speculation about extra cooling systems pointless. And this is what has made the problem so difficult.
I suspect that the problem is in fact in the cells - not necessarily that GS Yuasa "screwed up", that is, permitted a flaw that was known to be wrong, but that some unknown, and therefore uncontrolled and uncontrollable, aspect of production or materials changed.
More interesting than the solution is how can an aircraft go thru nearly 2 years or rigors testing, knowing that the batteries are new technology with specific pitfalls, go into service for less than a year and have several of these dramatic failures. Who is minding the store?
IMHO these batteries failures are inexcusable engineering failures. Could these failures have happened in the air as easily as they did on the ground? Do some people need to be fired?
Republican In Name Only! And he works for the current administration, so...
If the FAA does approve a corrective action plan (understanding that this is an unknown time variable), how long do you think it would be for the 787's that are grounded to be flying again? I assume that the existing fleet would get priority fixes, but would they be fixed where they sit, or would they have to get waivers to fly back to Boeing?
In my mind, even after an approved corrective action, this could be a while before these are seen in commercial use again!
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