The solution seems to be liquid vs. air cooling. The article states that air is less dense at higher altitudes and is less efficient in cooling anything even though it's at a lower temperature. Volt has gone to liquid cooling that works. What is Boeing waiting for? Call the GM engineers and find out what they did. A Volt did go on fire a little while ago.
Yes, Gorksi, it's a matter of liquid versus air cooling. It's also a matter of passive versus active cooling. As far as we can tell, Boeing is using passive air cooling. There reportedly are no fans to draw the hot air away. Toyota uses air cooling on its Prius PHV, but it is active air cooling -- they use three fans to draw the heat away from the battery's cells.
I don't know how much it would cost to add liquid cooling, Cabe. In today's electric cars and plug-in hybrids, packaging is said to be about 50% of the cost of the entire battery package. How much that differs between passive and active cooling situations, I don't know. Whatever the cost, though, the production volumes for a 787 are ridiculously small compared to those of a production car, so the cost wouldn't be multiplied by hundreds of thousands of units.
Liquid cooling is not my favorite solution. The thermal energy developed during lithium ion battery charge discharge cycles should be just moved away from the source. To obtain an efficient thermal energy transport the use of heat pipes will bring much more benefit. In case of battery thermal runaway the water system will be a big, big problem.
Thermal runaway occurs at 120 -200 deg. Celsius, is a strong exoterm reaction which can not stop until all active material is consumed. Actually is the liquid electrolyte which starts decompose. The only commercial available technology able to transfer more than100 watt/ cm2 is the heat pipe. Boeing should have experience with this technology. It was extensive in the spacecraft technology to cool the sunside of a spaceship (transfer the heat from the hot to the cool side). More than that the heat can be transferred to a heat exchanger outside the battery walls (trough the firewalls). Another system should be also included to cool down the cells at bellow 20 degrees Celsius where the liquid electrolyte ions stop to move (available for the military technology). This approach is possible to be implemented with special designed hot pipes at reduced volumes. The space for the cooling pipes (integrated into cooling plates between the cells) is the same as with the current (empty space between the cells) Boeing solution. Yes, Walter can be dangerous, if water comes in contact with battery electrodes the battery will explode.
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
Boeing used Lithium systems to reduce weight...liquid cooling just increases weight and the Law of Diminishing Returns suggests that changing the battery system may be the only solution and that involves recertification....a long process.
Internal shorts in cells. Again, in Duracell, zinc dendrites (analagous to stalactites) growing within the cell pierce the separator and create a soft short which becomes gradually worse until the cell dies. There are indications that some researchers are working on reducing dendrite growth in lithium systems. Was dendrite growth the problem in the 787 system?
You've been all over this story, Chuck, and it seems like it will continue for awhile. Great coverage. I agree that it seems to be a liquid vs. air debate. Perhaps some of the latest research I've covered about lithium-ion battery design could be helpful in terms of what best way to design the battery so this doesn't happen again. I guess it's a little too late to start from scratch, though, so Boeing will have to fix the problem based on what it's already done.
Liquid versus air cooling? The present battery has no effective cooling system of any kind as far as I can tell. The case provides conductive cooling and any outside air provides passive convection cooling of the case and that is it. The cells could bake each other with no effective cooling within the battery.
Boeing needs to maintain the energy to weight ratio. So, no other battery chemistry or more complex cooling system is practical for their design goal. Internal heat pipes connected to a cold plate on one side of the case could help reduce internal cell temperature but would add weight and would most likely require active cooling outside the case. So, it looks like they'll be opting for a more fireproof containment, more space between cells and maybe an external venting system to keep the case from rupturing and smoke from pouring into the cabin. Band-aid approach?
This alone will not prevent catastrophic battery failure but will permit them to live with occassional battery failures without endangering the aircraft. Or at least that's what they may be hoping for. The time bought will permit them to eventually phase in a full redesign of the battery system. That's what I'm hoping for.
I think lithium ion batteries should be used only with air cooling and only in ground. While flying, the conventional acid lead batteries can be used alternatively. Why ?During flying some moving energy of the engines can be used energy source, and there is no need big batteries while flying. Water cooling can bring some complex failure initialization in mean time and water must be capsulated very well, if the water face with low atmospheric pressure it can easliy vaporuised and this can generate contamination, dirtiness and aging problems. Air cooling can always be problem in high altitudes, because there is no enough air.
I'll bet Nissan is watching this Boeing incident with great interest. In Florida, I'm hearing the 100 mile range of the Leaf is more like 70 miles due primarily due to the inefficient air cooled batteries - and of course the use of air conditioning.
This is just one more reason I'm glad I chose a Volt 2 years ago . . .
I work in the aircraft industry as an elec. eng. for helicopters and (to quote GM's advert. slogan) what is "Tried, Tested and True" are the ubiquitous lead acid batteries. Intuitively, I've felt that the choice of going to Li-ion in the air wasn't worth the weight/E-density savings. Heck, even transporting Li-ion batteries as air-cargo is a huge issue! Appears to me that weight savings can be made in MANY other places than the main battery source....right? What happens in the situation where the aircraft reverts to battery power only...high currents to run all basic systems when you need them the most and everyone is feeling good because Boeing vented battery smoke to the outside?? What? That's part of the proposed fix? Wow...! I believe that the use of Li-ion batteries in the auto industry is sound. One can always stop the car, get out and watch her burn if the battery pack heads south; not so for aircraft. "Tried, tested and true" should be the slogan for designing aircraft, not "let's try, let's test, let's push certification, oh-oh it's not true".
Many times what we think might be better is not better. The fact that the speak around Li-ion technology is: fire, smoke, explosions, unstable, thermal runaway, advanced cooling, etc. should make designers think twice. Li-ion batteries in space...is a trade off where weight to push 'er into space is critical and energy usage while in space is carefully managed.
To me, it's a no brainer. When we can make lap-tops work reliably without lap fire incidents, then perhpas Li-ion technology can move to the air.
Hope Boeing contributed to the correct political campaign! Then Ray Lahood may well approve. Seems the SC "right to work" move may also affect their approval for the fix.
I know, should not be a political thing but a design decision. But just wanted to throw out some reality of the bureaucracy climate.
I like your point. Driving and flying with Li batteries are not the same animal! I might be very disappointed to see my expensive car burn up. Not so much if my plane burned up (but then my wife would be rich from the life insurance).
Heh...heh. Yeah, but if the ins. co. found out that you flew knowing the published issues/dangers, they might not honour the claim, many don't cover suicide!
I was thinking that instead of cooling or smoke venting systems, they should just make a break away battery with a trap door and drop it out the bottom of the aircraft, that'd do it right? It could catch fire at anytime then. Let's face it, how many times do we actually need only battery power... :-) Yeah, the battery burning at terminal velocity through moist air is kinda like a meteorite. Funny, mention an idea like that and everyone would laugh, but venting smoke is a viable cure?
But those extra large windows and extra cushioning with wine holders in first class sure makes me feel better about flying the DLiner.
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!
"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.
I'm dubious even about the need for liquid cooling in a case like this. Correct me if I'm wrong, but do we even know that the cells reached a high temperature PRIOR TO the fires? This is critical. I assume the battery management system monitors the cell temperatures. If it does, and the cells had reached a high temperature, I'm guessing this would have been announced already. And if the problem occurred without a prior high temperature, then something else, presumably internal to the cell that caught fire, was the cause, and liquid cooling would be superfluous.
I've gone through the NTSB's interim report, Jeffrey, and there's no reference to earlier high temperatures, so I can't answer the question. For what it's worth, though, The Wall Street Journal reported that the temperature during the JAL incident hit 1,250 degrees F.
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.
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?
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?
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.
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