Oils4AsphaultOnly
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Re: Toyota Mirai Fuel Cell

Thu Jun 13, 2019 8:54 pm

GRA wrote:
Oils4AsphaultOnly wrote:
GRA wrote:GCR: https://www.greencarreports.com/news/1123535_toyota-mirai-gets-deepest-discount-yet-in-the-midst-of-hydrogen-shortage

SQL errors so can't quote, but it's weird considering the H2 situation in the Bay Area right now. You'd think they'd do as they're doing in Norway, and simply stop sales for a while. Maybe this is driven by needing emission credits.


At first it didn't make sense to me. Why would Norway's fueling station explosion (why didn't you link it?) impact Bay Area Mirai sales.

I put it in the general "Hydrogen and FCEVs discussion" topic rather than one of the specific FCEV topics, as fuel shortages apply to all FCEVs. OTOH, the Bay Area fire and shortage was discussed in the either that or California retail H2 stations topic, forget which. cwerdna first posted that one, as I didn't see it until the next day.

Oils4AsphaultOnly wrote:Then I found out about the Santa Clara explosion: https://abc7news.com/bay-area-hydrogen- ... n/5328775/

In the case of Norway, I've pointed out before how dangerous extremely high compression (10,000 psi or 70bar) was, and now the Norway explosive decompression bears it out. People nearby were injured because their airbags deployed from the shockwave of the explosive decompression! Compressed H2 tanks should NOT be roaming around on the highways as any ruptures will affect any vehicle within its blast radius.

And gasoline-fueled ICEs shouldn't be roaming our streets and highways, because they can catch on fire/explode. See my comments in the H2 and FCEVs topic: https://www.mynissanleaf.com/viewtopic.php?f=7&t=14744&start=4220#p559990


Oils4AsphaultOnly wrote:Just google for Russian CNG explosion videos for just a sampling of what 3500psi decompression can do (no flame needed). sample: https://www.youtube.com/watch?v=5-nOPvXiIWQ

Toyota needs to end their obsession with FCEV's and put more effort into their BEV and PHEV vehicles.

Right, so then they can worry about batteries experiencing thermal runaway, catching fire and/or exploding: https://www.youtube.com/watch?time_continue=16&v=AmbHpqWjMVE

This is one of the reasons why Toyota wants to develop solid-state batteries, as they should be much less susceptible to this. Without exception, all of these energy storage methods are hazardous in one way or another. If you want to avoid any possibility of fire or explosion, then you need to use propulsion that doesn't rely on energy stored at high densities. Walk, bike, skate, paddle, sail, rollerblade, swim, etc.


That's a false equivalence. Gasoline fires are explosive if you aerate it (think gasoline fumes in a partially empty tank), otherwise they burn. BEV fires are slow to conflate and generally self-immolate (the china model S explosion was because of poor ventilation that allowed the fumes to pool around the car before igniting - it's a very unlikely situation much like how corn starch is also explosive yet unlikely to do so) - good job on finding the only one example out of the almost a million BEV's on the road. H2 and CNG explosive tank risks are structurally inherent to the design. On top of that, the tank failure happens suddenly and without warning (for both Santa Clara and Norway), giving bystanders zero chance to take any precautions.

Your blind Faith to H2 is clouding your judgement.
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mux
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Re: Toyota Mirai Fuel Cell

Thu Jun 13, 2019 11:10 pm

The thing is though, and at the risk of sounding apologetic to CNG or H2, you can design and maintain to reduce those kinds of failures to close to zero. Most CNG tank explosions you're going to see are in very old, badly maintained vehicles. Same should be true for hydrogen at a certain point in the future.

The issue I have with hydrogen in this regard isn't that it is inherently dangerous to have an extremely explosive gas, with on top of that a good 10% of its embodied energy just in gas pressure added to that. It's the fact that you NEED to maintain, inspect and replace these tanks. It is an inherently fragile chain of trust to get to high reliability.

And it gets worse, from an engineering perspective at least. Most tanks are made from carbon fiber reinforced plastics, not metals. CFRP is extremely strong but brittle, meaning any failure will actually be catastrophic. There are ways to design much more ductile materials in there to reduce this risk and limit 'wear and tear' failures to (quite fast) leaks instead of explosive decompression. But these tanks would be unreasonably heavy to put in a car (rough rule of thumb: about ~2.5x the weight of CFRP tanks, which already weigh about 100kg for the Nexo and Mirai).

All of this isn't as much of an indictment of hydrogen as vehicle fuel as Oils4AsphaultOnly implies though. Things can, should and certainly will be engineered to be safe. But clearly, right now, it isn't. Worldwide there are about 100 commercial hydrogen vending stations and about 5000 currently running H2 vehicles. So far we've had 2 stations catastrophically fail. This is an unreasonable failure rate. If this were the aerospace industry, EVERYTHING would be shut down. This is an enormous deal. I think the industry is just 1 Mirai exploding away from basically shutting down.

GRA
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Re: Toyota Mirai Fuel Cell

Sat Jun 15, 2019 3:57 pm

Oils4AsphaultOnly wrote:
GRA wrote:
Oils4AsphaultOnly wrote:
At first it didn't make sense to me. Why would Norway's fueling station explosion (why didn't you link it?) impact Bay Area Mirai sales.

I put it in the general "Hydrogen and FCEVs discussion" topic rather than one of the specific FCEV topics, as fuel shortages apply to all FCEVs. OTOH, the Bay Area fire and shortage was discussed in the either that or California retail H2 stations topic, forget which. cwerdna first posted that one, as I didn't see it until the next day.

Oils4AsphaultOnly wrote:Then I found out about the Santa Clara explosion: https://abc7news.com/bay-area-hydrogen- ... n/5328775/

In the case of Norway, I've pointed out before how dangerous extremely high compression (10,000 psi or 70bar) was, and now the Norway explosive decompression bears it out. People nearby were injured because their airbags deployed from the shockwave of the explosive decompression! Compressed H2 tanks should NOT be roaming around on the highways as any ruptures will affect any vehicle within its blast radius.

And gasoline-fueled ICEs shouldn't be roaming our streets and highways, because they can catch on fire/explode. See my comments in the H2 and FCEVs topic: https://www.mynissanleaf.com/viewtopic.php?f=7&t=14744&start=4220#p559990


Oils4AsphaultOnly wrote:Just google for Russian CNG explosion videos for just a sampling of what 3500psi decompression can do (no flame needed). sample: https://www.youtube.com/watch?v=5-nOPvXiIWQ

Toyota needs to end their obsession with FCEV's and put more effort into their BEV and PHEV vehicles.

Right, so then they can worry about batteries experiencing thermal runaway, catching fire and/or exploding: https://www.youtube.com/watch?time_continue=16&v=AmbHpqWjMVE

This is one of the reasons why Toyota wants to develop solid-state batteries, as they should be much less susceptible to this. Without exception, all of these energy storage methods are hazardous in one way or another. If you want to avoid any possibility of fire or explosion, then you need to use propulsion that doesn't rely on energy stored at high densities. Walk, bike, skate, paddle, sail, rollerblade, swim, etc.

That's a false equivalence. Gasoline fires are explosive if you aerate it (think gasoline fumes in a partially empty tank), otherwise they burn. BEV fires are slow to conflate and generally self-immolate (the china model S explosion was because of poor ventilation that allowed the fumes to pool around the car before igniting - it's a very unlikely situation much like how corn starch is also explosive yet unlikely to do so) - good job on finding the only one example out of the almost a million BEV's on the road. H2 and CNG explosive tank risks are structurally inherent to the design. On top of that, the tank failure happens suddenly and without warning (for both Santa Clara and Norway), giving bystanders zero chance to take any precautions.

Your blind Faith to H2 is clouding your judgement.

Thermal runaway is hardly limited to a sole occurrence, as numerous videos and accounts of Teslas immolating themselves (sometimes repeatedly) has shown. And I've certainly never claimed that H2 is inherently safe, or that high compression storage is the safest method; indeed, I've said (in the H2 and FCEVs topic, and possibly others) that the ultimate goal for FCEVs is low pressure storage through adsorption or nanotubes, if either can be made to work economically, for both safety and design reasons, as LP storage allows use of tanks shaped to fit the car (especially in a skateboard configuration), rather than cylindrical ones for strength. Here's one such post from 2013, but you can find many others from me if you search for "adsorption nano-tube" with me as the poster: https://www.mynissanleaf.com/viewtopic.php?f=10&t=14638&p=332079&hilit=adsoprtion+nano+tube#p332079

I note, however, that the front seat occupants in your video were able to exit the vehicle, apparently uninjured (hard to say for sure; IDK if anyone was in the back, where injuries would be more likely.

The issue is whether or not high pressure storage, like Li-ion batteries, is adequately safe, not whether or not either is completely safe, and that can only be determined statistically as well as in the court of public opinion. In the specific case of the video you provided, what other info do we have? What kind of tank was in use? Why did it fail? Had it been repaired? How old was it? Was it required to be pressure-tested, and had it passed, etc.? Given that this was apparently in Russia, a country with a notoriously lax and corrupt safety regime, how much relevance does this particular example have to countries with tighter standards and enforcement? And so on.

As to blind faith in H2, I have none. I value it for allowing FCEVs to be ZEVs, and for its operational advantages over BEVs (for now), of greater range, rapid energy replenishment and because it allows dividing energy replenishment from where you live or work, until such time as:

1. recharging stations are universal or

2. We replace virtually the entire fleet with fewer, autonomous MaaS BEVs that can drive themselves to/from charging stations.

The capabilities that FCEVs provide will allow people living in MUDs in dense urban areas in Asia, Africa and South America, which will see the majority of population growth between now and 2050, plus Europe, to use ZEVs, something that won't be possible with privately-owned BEVs alone for decades.

FCEVs also happen to fit my own use case better than BEVs at the moment, but I have no emotional connection to either tech, let alone blind faith. They both have advantages and disadvantages, and I'll be satisfied if either or both succeed commercially. My primary goal is to get off fossil fuels, and we need at least one ZEV tech that can be successful without subsidy or mandate; neither of the above are as yet.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

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Oils4AsphaultOnly
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Re: Toyota Mirai Fuel Cell

Sat Jun 15, 2019 6:32 pm

GRA wrote:
Oils4AsphaultOnly wrote:
GRA wrote:I put it in the general "Hydrogen and FCEVs discussion" topic rather than one of the specific FCEV topics, as fuel shortages apply to all FCEVs. OTOH, the Bay Area fire and shortage was discussed in the either that or California retail H2 stations topic, forget which. cwerdna first posted that one, as I didn't see it until the next day.


And gasoline-fueled ICEs shouldn't be roaming our streets and highways, because they can catch on fire/explode. See my comments in the H2 and FCEVs topic: https://www.mynissanleaf.com/viewtopic.php?f=7&t=14744&start=4220#p559990


Right, so then they can worry about batteries experiencing thermal runaway, catching fire and/or exploding: https://www.youtube.com/watch?time_continue=16&v=AmbHpqWjMVE

This is one of the reasons why Toyota wants to develop solid-state batteries, as they should be much less susceptible to this. Without exception, all of these energy storage methods are hazardous in one way or another. If you want to avoid any possibility of fire or explosion, then you need to use propulsion that doesn't rely on energy stored at high densities. Walk, bike, skate, paddle, sail, rollerblade, swim, etc.


That's a false equivalence. Gasoline fires are explosive if you aerate it (think gasoline fumes in a partially empty tank), otherwise they burn. BEV fires are slow to conflate and generally self-immolate (the china model S explosion was because of poor ventilation that allowed the fumes to pool around the car before igniting - it's a very unlikely situation much like how corn starch is also explosive yet unlikely to do so) - good job on finding the only one example out of the almost a million BEV's on the road. H2 and CNG explosive tank risks are structurally inherent to the design. On top of that, the tank failure happens suddenly and without warning (for both Santa Clara and Norway), giving bystanders zero chance to take any precautions.

Your blind Faith to H2 is clouding your judgement.



Thermal runaway is hardly limited to a sole occurrence, as numerous videos and accounts of Teslas immolating themselves (sometimes repeatedly) has shown.


That wasn't what I meant. I thought it was pretty obvious that It was the explosive self-immolation that has only been one occurance, since the context was about how you've established a false equivalence between fires and explosions, and my examples were all about explosions. Silly me for thinking you'd keep things in context.

GRA wrote:And I've certainly never claimed that H2 is inherently safe, or that high compression storage is the safest method; indeed, I've said (in the H2 and FCEVs topic, and possibly others) that the ultimate goal for FCEVs is low pressure storage through adsorption or nanotubes, if either can be made to work economically, for both safety and design reasons, as LP storage allows use of tanks shaped to fit the car (especially in a skateboard configuration), rather than cylindrical ones for strength. Here's one such post from 2013, but you can find many others from me if you search for "adsorption nano-tube" with me as the poster: https://www.mynissanleaf.com/viewtopic.php?f=10&t=14638&p=332079&hilit=adsoprtion+nano+tube#p332079


I wasn't aware that you felt this negatively about H2 storage, considering how vehemently you've been defending FCEV's. It's just such a contradictory position to hold, since all current FCEV's have relied on high-pressure H2 tanks.

GRA wrote:I note, however, that the front seat occupants in your video were able to exit the vehicle, apparently uninjured (hard to say for sure; IDK if anyone was in the back, where injuries would be more likely.


They survived (but aren't injury free due to the debris), because it was the pressure wave that blew out the trunk and windows, and not pieces of the tank. That's why I hate FCEV proponents who claim that there are barriers in place to protect the occupants in case of an "explosion". Shockwaves aren't inhibited by barriers! Also remember that the video is of a 3500psi CNG tank. An H2 tank (at 10,000psi) would have been much more destructive as evidenced by the Norway explosion!

GRA wrote:The issue is whether or not high pressure storage, like Li-ion batteries, is adequately safe, not whether or not either is completely safe, and that can only be determined statistically as well as in the court of public opinion. In the specific case of the video you provided, what other info do we have? What kind of tank was in use? Why did it fail? Had it been repaired? How old was it? Was it required to be pressure-tested, and had it passed, etc.? Given that this was apparently in Russia, a country with a notoriously lax and corrupt safety regime, how much relevance does this particular example have to countries with tighter standards and enforcement? And so on.

As to blind faith in H2, I have none. I value it for allowing FCEVs to be ZEVs, and for its operational advantages over BEVs (for now), of greater range, rapid energy replenishment and because it allows dividing energy replenishment from where you live or work, until such time as:

1. recharging stations are universal or

2. We replace virtually the entire fleet with fewer, autonomous MaaS BEVs that can drive themselves to/from charging stations.

The capabilities that FCEVs provide will allow people living in MUDs in dense urban areas in Asia, Africa and South America, which will see the majority of population growth between now and 2050, plus Europe, to use ZEVs, something that won't be possible with privately-owned BEVs alone for decades.

FCEVs also happen to fit my own use case better than BEVs at the moment, but I have no emotional connection to either tech, let alone blind faith. They both have advantages and disadvantages, and I'll be satisfied if either or both succeed commercially. My primary goal is to get off fossil fuels, and we need at least one ZEV tech that can be successful without subsidy or mandate; neither of the above are as yet.


Baloney! You're trying to set up an equivalent judgement criteria that's not equivalent and pointless. The fact that you're trying to set that up, shows that you really don't have an issue with high-pressure storage and that your words above were empty. If you still don't get the difference, then I'm wasting my time.
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mux
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Re: Toyota Mirai Fuel Cell

Sun Jun 16, 2019 12:14 am

Really, the big difference between a CNG and H2 tank isn't even the absolute difference in pressure, it's the embodied energy. Natural gas compresses very easily and decompresses fairly benignly because it forms a supercritical fluid at 45 bars, sapping away a decent amount of the compression energy. Upon decompression, consequently, you end up not just with methane in gas form but also a lot of (very cold) liquid at basically atmospheric pressure turning into gas much slower. Effectively, this means that even a 200 bar/3k psi CNG tank will produce a shockwave very similar to an air/nitrogen/h2/whatever tank compressed to about 50 bar.

This doesn't happen to H2. Hydrogen doesn't form anything but a gas down to nearly absolute zero, so ALL of the energy contained in that compression is released upon failure of the tank.

In terms of the energy contained in the shockwave of an explosively decompressing tank, it's not the difference between 200 and 700 bar, it's the difference between 50 and 700. This is why you can walk away basically unscathed from a CNG tank explosion inside your car, but a H2 tank explosion a couple dozen meters away will set off your air bags and cause some considerable personal injury to anyone within a few meters.

Don't forget; there's about 10-15% of the embodied energy of the hydrogen just in compression inside that tank. For a 2.5kg tank (like in the Mirai or Nexo), that's 8kWh or 30MJ of energy that will be distributed over mechanical deformation and a shockwave. This is equivalent to 8kg of TNT detonating in your car.

None of this is to scare anyone per se; any concentrated form of energy will present a risk, but just to put this conversation into context. A H2 tank explosion is not like the CNG tank explosion on video, it's ten times worse.

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Re: Toyota Mirai Fuel Cell

Sun Jun 16, 2019 4:36 pm

Oils4AsphaultOnly wrote:
GRA wrote:And I've certainly never claimed that H2 is inherently safe, or that high compression storage is the safest method; indeed, I've said (in the H2 and FCEVs topic, and possibly others) that the ultimate goal for FCEVs is low pressure storage through adsorption or nanotubes, if either can be made to work economically, for both safety and design reasons, as LP storage allows use of tanks shaped to fit the car (especially in a skateboard configuration), rather than cylindrical ones for strength. Here's one such post from 2013, but you can find many others from me if you search for "adsorption nano-tube" with me as the poster: https://www.mynissanleaf.com/viewtopic.php?f=10&t=14638&p=332079&hilit=adsoprtion+nano+tube#p332079

I wasn't aware that you felt this negatively about H2 storage, considering how vehemently you've been defending FCEV's. It's just such a contradictory position to hold, since all current FCEV's have relied on high-pressure H2 tanks.

GRA wrote:I note, however, that the front seat occupants in your video were able to exit the vehicle, apparently uninjured (hard to say for sure; IDK if anyone was in the back, where injuries would be more likely.


They survived (but aren't injury free due to the debris), because it was the pressure wave that blew out the trunk and windows, and not pieces of the tank. That's why I hate FCEV proponents who claim that there are barriers in place to protect the occupants in case of an "explosion". Shockwaves aren't inhibited by barriers! Also remember that the video is of a 3500psi CNG tank. An H2 tank (at 10,000psi) would have been much more destructive as evidenced by the Norway explosion!

GRA wrote:The issue is whether or not high pressure storage, like Li-ion batteries, is adequately safe, not whether or not either is completely safe, and that can only be determined statistically as well as in the court of public opinion. In the specific case of the video you provided, what other info do we have? What kind of tank was in use? Why did it fail? Had it been repaired? How old was it? Was it required to be pressure-tested, and had it passed, etc.? Given that this was apparently in Russia, a country with a notoriously lax and corrupt safety regime, how much relevance does this particular example have to countries with tighter standards and enforcement? And so on.

As to blind faith in H2, I have none. I value it for allowing FCEVs to be ZEVs, and for its operational advantages over BEVs (for now), of greater range, rapid energy replenishment and because it allows dividing energy replenishment from where you live or work, until such time as:

1. recharging stations are universal or

2. We replace virtually the entire fleet with fewer, autonomous MaaS BEVs that can drive themselves to/from charging stations.

The capabilities that FCEVs provide will allow people living in MUDs in dense urban areas in Asia, Africa and South America, which will see the majority of population growth between now and 2050, plus Europe, to use ZEVs, something that won't be possible with privately-owned BEVs alone for decades.

FCEVs also happen to fit my own use case better than BEVs at the moment, but I have no emotional connection to either tech, let alone blind faith. They both have advantages and disadvantages, and I'll be satisfied if either or both succeed commercially. My primary goal is to get off fossil fuels, and we need at least one ZEV tech that can be successful without subsidy or mandate; neither of the above are as yet.

Baloney! You're trying to set up an equivalent judgement criteria that's not equivalent and pointless. The fact that you're trying to set that up, shows that you really don't have an issue with high-pressure storage and that your words above were empty. If you still don't get the difference, then I'm wasting my time.

Oh, I get the difference, but you're right, I don't consider that HP storage is as yet, proven to be unacceptably safe. Of course, I sleep less than six feet from a couple of steel scuba tanks filled to 3,500 PSI, which were used when I bought them and are now 12 years older. They are right next to a pair of 2,400 PSI steel tanks, also bought used (actually, they can legally be overfilled 10% to 2,640, and I do so) with the same 12 years of use by me, and the latter should be safer AOTBE, so I've undoubtedly decided that the advantages of HP storage (smaller size and weight, better buoyancy characteristics) outweigh the disadvantages in many cases, even though I have no doubt that if any of them were to rupture, any shrapnel would penetrate the wall of the closet without difficulty and be able to reach me, with serious consequences if it did.

Of course, they are all required to be visually inspected as well as having their valves (normal and burst) maintained on a yearly basis, and hydro-pressure tested every five years. There are probably hundreds of thousands if not millions of these in use worldwide with explosive ruptures being extremely rare, so I have more than a little basis for my judgement, but it would undoubtedly be safer to store them further away from me, and if I could, I would.

It's a question of relative risk. For instance, Teslas have experienced a fair number battery fires involving thermal runaway, apparently at a much greater rate than the batteries used by other ZEV manufacturers, although it's possible that Tesla fires are more likely to be reported, and also that there are just more of them out there. Here's a list up to May of last year, although many of these fall into the "well, duh" category where the fires were the least of the problem: https://www.autoblog.com/2018/05/11/a-list-of-tesla-car-fires-since-2013/
Then we had this last month:
Tesla pushes battery software update after recent fires

The over-the-air update is going out to Model S and X cars now ‘out of an abundance of caution’
https://www.theverge.com/2019/5/16/18627746/tesla-fire-battery-software-update-model-s-x

This includes the car in the video I linked to, and another one in Hong Kong in a "parking lot" (given the density of Hong Kong, i wonder if that should be "parking garage", as in the case in Shanghai). Both caught fire while parked.

Tesla packs have the highest specific energy and energy density of any BEV batteries on the market, so even assuming no differences in chemistry or thermal protection (which is not the case), you'd expect them to have a higher rate of fires. Does this mean that I think Tesla batteries are unacceptably safe? No, just less safe than others, and almost certainly still safer than fossil fuels, especially gasoline.

From memory, there are something like 240,000 vehicle fires ranging from minor to catastrophic in the U.S annually, out of a fleet of something over 250M motor vehicles. Since I don't know what percentage of those fires were caused by the loads or external sources rather than inherent to the vehicle, let's just assume they are all inherent and figure a round number of 1 veh. fire/per 1,000 veh./year for fossil-fueled ICEs. From over 100 years of knowledge and experience, we know the public and the government both judge this rate to be acceptably safe, although any steps to improve it will be welcome.

The most recent number I saw for the FCEV fleet in California was 6,300. Let's lump both H2 fires and tank ruptures together; if the rate is under 1/1,000, it will be adjudged acceptably safe. That means that this year, if we have 7 or more such accidents it would be less safe than fossil-fueled ICEs. Production FCEVs have been on the market in California for I think it's 5 years now, and I haven't heard of a single such case, although we could have had something like 10-15 total and still be no less safe than ICEs. There's no doubt that if one did happen we'd hear about it, just as we did in the case of the H2 production and fill station explosions and fires, with references to the Hindenburg and much hand-wringing. There have been no such reports.

Now, if tanks start blowing right and left and/or people start getting barbequed in their FCEVs on a regular basis at a much higher rate than ICEs, then we'd have reason to think that HP H2-fueled FCEVs aren't adequately safe, and I'd be among the first to say pull them from the fleet, but we have no such evidence as yet. Until we do, I'm okay with them on the road, although I'd certainly prefer that one of the LP H2 storage techs gets commercialized and replaces them; LP is safer than HP, AOTBE. YMMV, but do base the decision on statistical evidence rather than gut feeling.
Guy [I have lots of experience designing/selling off-grid AE systems, some using EVs but don't own one. Local trips are by foot, bike and/or rapid transit].

The 'best' is the enemy of 'good enough'. Copper shot, not Silver bullets.

SageBrush
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Re: Toyota Mirai Fuel Cell

Sun Jun 16, 2019 5:30 pm

GRA wrote:The most recent number I saw for the FCEV fleet in California was 6,300. Let's lump both H2 fires and tank ruptures together; if the rate is under 1/1,000, it will be adjudged acceptably safe.

You are making two assumptions that are incorrect:

1. That the ICE fire and high pressure H2 fire have similar characteristics and consequences
2. That the 6,300 FCEV fleet has a year of driving as a denominator.
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Oils4AsphaultOnly
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Re: Toyota Mirai Fuel Cell

Sun Jun 16, 2019 9:14 pm

... prior context trimmed for brevity as acknowledgement of LeftieBiker's point ... I had more to say in my original response, but then felt that the single point was sufficient.

GRA wrote:Oh, I get the difference, but you're right, I don't consider that HP storage is as yet, proven to be unacceptably safe. Of course, I sleep less than six feet from a couple of steel scuba tanks filled to 3,500 PSI, which were used when I bought them and are now 12 years older. They are right next to a pair of 2,400 PSI steel tanks, also bought used (actually, they can legally be overfilled 10% to 2,640, and I do so) with the same 12 years of use by me, and the latter should be safer AOTBE, so I've undoubtedly decided that the advantages of HP storage (smaller size and weight, better buoyancy characteristics) outweigh the disadvantages in many cases, even though I have no doubt that if any of them were to rupture, any shrapnel would penetrate the wall of the closet without difficulty and be able to reach me, with serious consequences if it did.

Of course, they are all required to be visually inspected as well as having their valves (normal and burst) maintained on a yearly basis, and hydro-pressure tested every five years. There are probably hundreds of thousands if not millions of these in use worldwide with explosive ruptures being extremely rare, so I have more than a little basis for my judgement, but it would undoubtedly be safer to store them further away from me, and if I could, I would.

It's a question of relative risk. For instance, Teslas have experienced a fair number battery fires involving thermal runaway, apparently at a much greater rate than the batteries used by other ZEV manufacturers, although it's possible that Tesla fires are more likely to be reported, and also that there are just more of them out there. Here's a list up to May of last year, although many of these fall into the "well, duh" category where the fires were the least of the problem: https://www.autoblog.com/2018/05/11/a-list-of-tesla-car-fires-since-2013/
Then we had this last month:
Tesla pushes battery software update after recent fires

The over-the-air update is going out to Model S and X cars now ‘out of an abundance of caution’
https://www.theverge.com/2019/5/16/18627746/tesla-fire-battery-software-update-model-s-x

This includes the car in the video I linked to, and another one in Hong Kong in a "parking lot" (given the density of Hong Kong, i wonder if that should be "parking garage", as in the case in Shanghai). Both caught fire while parked.

Tesla packs have the highest specific energy and energy density of any BEV batteries on the market, so even assuming no differences in chemistry or thermal protection (which is not the case), you'd expect them to have a higher rate of fires. Does this mean that I think Tesla batteries are unacceptably safe? No, just less safe than others, and almost certainly still safer than fossil fuels, especially gasoline.

From memory, there are something like 240,000 vehicle fires ranging from minor to catastrophic in the U.S annually, out of a fleet of something over 250M motor vehicles. Since I don't know what percentage of those fires were caused by the loads or external sources rather than inherent to the vehicle, let's just assume they are all inherent and figure a round number of 1 veh. fire/per 1,000 veh./year for fossil-fueled ICEs. From over 100 years of knowledge and experience, we know the public and the government both judge this rate to be acceptably safe, although any steps to improve it will be welcome.

The most recent number I saw for the FCEV fleet in California was 6,300. Let's lump both H2 fires and tank ruptures together; if the rate is under 1/1,000, it will be adjudged acceptably safe. That means that this year, if we have 7 or more such accidents it would be less safe than fossil-fueled ICEs. Production FCEVs have been on the market in California for I think it's 5 years now, and I haven't heard of a single such case, although we could have had something like 10-15 total and still be no less safe than ICEs. There's no doubt that if one did happen we'd hear about it, just as we did in the case of the H2 production and fill station explosions and fires, with references to the Hindenburg and much hand-wringing. There have been no such reports.

Now, if tanks start blowing right and left and/or people start getting barbequed in their FCEVs on a regular basis at a much higher rate than ICEs, then we'd have reason to think that HP H2-fueled FCEVs aren't adequately safe, and I'd be among the first to say pull them from the fleet, but we have no such evidence as yet. Until we do, I'm okay with them on the road, although I'd certainly prefer that one of the LP H2 storage techs gets commercialized and replaces them; LP is safer than HP, AOTBE. YMMV, but do base the decision on statistical evidence rather than gut feeling.


explosions and fires are not the same, so stop lumping them together.
Last edited by Oils4AsphaultOnly on Mon Jun 17, 2019 12:41 am, edited 3 times in total.
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LeftieBiker
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Re: Toyota Mirai Fuel Cell

Sun Jun 16, 2019 9:16 pm

Is it really necessary to quote half a page of replies just to post one sentence?
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Re: Toyota Mirai Fuel Cell

Sun Jun 16, 2019 10:56 pm

mux wrote:Really, the big difference between a CNG and H2 tank isn't even the absolute difference in pressure, it's the embodied energy. Natural gas compresses very easily and decompresses fairly benignly because it forms a supercritical fluid at 45 bars, sapping away a decent amount of the compression energy. Upon decompression, consequently, you end up not just with methane in gas form but also a lot of (very cold) liquid at basically atmospheric pressure turning into gas much slower. Effectively, this means that even a 200 bar/3k psi CNG tank will produce a shockwave very similar to an air/nitrogen/h2/whatever tank compressed to about 50 bar.

This doesn't happen to H2. Hydrogen doesn't form anything but a gas down to nearly absolute zero, so ALL of the energy contained in that compression is released upon failure of the tank.

VERY informative, thanks
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