Hydrogen availability
Discussion
Love the styling, far better than the Hyperion XP1 monstrosity.
The tank life is likely to be a function of the number of refills, so it might be feasible to design it for the life of the car, assuming these sorts of cars aren't doing hyper mileage.
I don't know enough about graphene to compare its to a more conventional composite structure subject to low cycle fatigue, it does sound pretty ambitious though, will be interesting to see if it becomes a reality.
The bit they haven't touched on is how they are going to extract the performance from the fuel cell/s.
Without a decent size battery, or some kind of supercapacitor array, how are they going to deliver acceleration and regenerative braking commensurate with this type of car?
In light of this, the 'half the weight of a battery alternative' claim seems very ambitious.
The tank life is likely to be a function of the number of refills, so it might be feasible to design it for the life of the car, assuming these sorts of cars aren't doing hyper mileage.
I don't know enough about graphene to compare its to a more conventional composite structure subject to low cycle fatigue, it does sound pretty ambitious though, will be interesting to see if it becomes a reality.
The bit they haven't touched on is how they are going to extract the performance from the fuel cell/s.
Without a decent size battery, or some kind of supercapacitor array, how are they going to deliver acceleration and regenerative braking commensurate with this type of car?
In light of this, the 'half the weight of a battery alternative' claim seems very ambitious.
anonymous said:
[redacted]
You might be right, but what I wouldn't discount is that sooner or later a hydrogen-powered car is going to be involved in a collision serious enough to rupture the tank/s, particularly if they are integral to the structure of the car. What happens when 700 bar of pressurised highly combustible gas is released and ignites simultaneously?
At least when petrol ignites, it has to vapourise before it burns, and given that it is being stored at ambient pressure, the rate of burn and degree of 'explosion' is controlled to some degree by the vapourisation.
The pressurised hydrogen explosion on the other hand is much more likely to result in a car and its passengers exploding into thousands of pieces over a large area rather than just 'bursting into flames'.
Let's just hope its not a high-speed head-on between two hydrogen powered cars...
anonymous said:
[redacted]
Yes Europe say a tank has a maximum life of 20 years, not a minimum.Here's a report of a US Mirai with a 'do not refuel after' sticker in it - https://www.google.com/amp/s/insideevs.com/news/32...
anonymous said:
[redacted]
I'm well aware of the benefits of several independent cylindrical tanks with regard to safety. I also have first-hand experience of the engineering challenges presented by highly pressurised combustible gases, which I'm pretty sure you don't.I was responding to the idea of integrating the tank into the main structure of the car.
Obviously I haven't seen the physical arrangement of this idea, but I'm not quite sure how you would avoid stress concentrations and load transfer into the tank walls. These things exacerbate the issues arising from low cycle fatigue in composite structures, again something I have first hand experience with.
These are engineering challenges that just add another layer of complexity into what is an already complex system. I wish I could live in ignorance and just comfort myself with a bit of googling, but alas, it's too late for that in my case.
anonymous said:
[redacted]
Yes. And it's also the main problem, because unlike simply solving problems with engineering, changing legislation is MUCH harder and more time consuming.Consider approaching the legislators with a request for your particular 700 bar H2 tanks to be given a 20 year life in legislative terms. Think what the legislators have to win, and what they have to loose. This is why in almost all cases the simple answer is "no" when you ask questions like this..........
Max_Torque said:
anonymous said:
[redacted]
Yes. And it's also the main problem, because unlike simply solving problems with engineering, changing legislation is MUCH harder and more time consuming.Consider approaching the legislators with a request for your particular 700 bar H2 tanks to be given a 20 year life in legislative terms. Think what the legislators have to win, and what they have to loose. This is why in almost all cases the simple answer is "no" when you ask questions like this..........
It is simple to recall, for example, the German vacuum cleaner manufacturers trying to strangle the likes of Dyson through regulation with limits on the power of motors or, in the UK, the industry persuading John Prescott to effectively mandate the scrapping of perfectly decent and maintainable boilers for those ghastly and inefficient condensing boilers with very limited effective lives and appalling whole life costs.
The car industry seems highly proficient at this.
anonymous said:
[redacted]
You are not actually reading what I wrote....It was you who originally said that hydrogen tanks integral to the structure of the car don't sound like a good idea.
Im agreeing with you.... and pointing out that non-cylindrical/more complex composite structures will likely have stress concentration points at the protrusion points to attach other parts of the car. An impact can then transfer external forces into the tank structure at the stress concentration, exactly where you don't want it.
I'm NOT talking about the cylindrical tanks in a 'regular' hydrogen car that have been tested as you have described, Im referring to the hydrogen supercar thingy above.
anonymous said:
[redacted]
er, the legislative limits are general directly driven by the probability curve for failure vs age. The legislators take the real life data and assign a legasltive life that reflects the level of risk they are comfortable with. They will certainly consider the worst case, and just because a tank "could" have a longer life under ideal circumstances does not me that any particular tank will have a longer life. The problem is that humans and fundamentally very poor at both assessing risk, but also appropriately reacting to it ( see Grenfell tower cladding for ref....) How many familys would you be happy to blow up by HP H2 tank failures per year for example?
Max_Torque said:
anonymous said:
[redacted]
er, the legislative limits are general directly driven by the probability curve for failure vs age. The legislators take the real life data and assign a legasltive life that reflects the level of risk they are comfortable with. They will certainly consider the worst case, and just because a tank "could" have a longer life under ideal circumstances does not me that any particular tank will have a longer life. The problem is that humans and fundamentally very poor at both assessing risk, but also appropriately reacting to it ( see Grenfell tower cladding for ref....) How many familys would you be happy to blow up by HP H2 tank failures per year for example?
The reality is that each one is subtly different due to small variations in humidity, temperature, operator experience/habit, machine settings, tool wear, contaminants, etc. during the manufacturing process. There is also the effect of variable environmental conditions, which may influence the rate of in-service moisture absorption and thermal degradation.
It's not impossible to see 25%+ variability of failure stress between two parts that look identical to the casual observer.
100% inspection using NDT methods to identify internal defects such as voids, inclusions and out of tolerance volume fractions to try to remove the worst offenders will help, but you then need to weight that against whatever scrap rate you are prepared to live with.
In a predominantly hoop wound composite structure that is pressurised internally, the failure mechanism to watch for is fatigue of the matrix (i.e. the glue holding it all together) near the inner wall where the radial 'crushing' force between fibres is highest. These forces cycle in magnitude during each discharge and refill, which speeds up the process of crack propagation, i.e. low cycle fatigue.
These cracks can propagate from microscopic defects, scratches or voids as mentioned earlier.
So despite the fact that the fibres themselves are seeing tensile loads an order of magnitude higher than the radial loads on the resin matrix, it's the later that typically limits the service life.
It's quite difficult to comprehend the magnitude of the forces involved. An internal pressure of 700 bar or 10000 psi equates to 700 kg force applied to every square cm of the internal surface. So each tank is containing a total 'force' of several thousand tons.
Edited by GT911 on Friday 13th August 00:43
I started the thread, re supply of hydrogen, ultimately hoping it would improve…
Well it has not!
Closure of Honda in Swindon removed that unreliable supply and the ITM fueling in Swindon closes today.
So basically the South West is stuffed, Heathrow and Birmingham the only options left.
;(
Can’t see many miles being put on the Nexo….
Well it has not!
Closure of Honda in Swindon removed that unreliable supply and the ITM fueling in Swindon closes today.
So basically the South West is stuffed, Heathrow and Birmingham the only options left.
;(
Can’t see many miles being put on the Nexo….
GT911 said:
anonymous][redacted said:
What happens when 700 bar of pressurised highly combustible gas is released and ignites simultaneously?
At least when petrol ignites, it has to vapourise before it burns, and given that it is being stored at ambient pressure, the rate of burn and degree of 'explosion' is controlled to some degree by the vapourisation.
The pressurised hydrogen explosion on the other hand is much more likely to result in a car and its passengers exploding into thousands of pieces over a large area rather than just 'bursting into flames'.
Let's just hope its not a high-speed head-on between two hydrogen powered cars...
ashenfie said:
Never seen a petrol car go up then. Next door had two car one petrol and diesel the diesel one had an electrical problem and court fire in the night burn slowly for a few hours which set the petrol one on fire which exploded. Luckily we saved their house and a few other nearby cars damaged. IMHO petrol and electric cars are quite dangerous in fires
Sure, I've seen a petrol car go up.What 99% of people will have never seen is what happens when pressurised hydrogen explodes.
It's a low probability scenario, but if it did happen, there would most likely be no house left to save.
The pressure wave from the explosion does most of the damage, not the fire.
ashenfie said:
GT911 said:
anonymous][redacted said:
What happens when 700 bar of pressurised highly combustible gas is released and ignites simultaneously?
At least when petrol ignites, it has to vapourise before it burns, and given that it is being stored at ambient pressure, the rate of burn and degree of 'explosion' is controlled to some degree by the vapourisation.
The pressurised hydrogen explosion on the other hand is much more likely to result in a car and its passengers exploding into thousands of pieces over a large area rather than just 'bursting into flames'.
Let's just hope its not a high-speed head-on between two hydrogen powered cars...
The issue with hydrogen is that as a gas, should it leak out slowly, it can form an ignitable mixture in air very easily (4 to 74% in air, vs 1.4 to 7.6% for gasoline) and the flame velocity for such a mixture is around 6 times faster than that of a gasoline vapour and air explosion.
A leak in a petrol tank generally simply sits locally in a puddle on the floor and evapourates, requiring a very local high energy ignition source to start it burning. A hydrogen leak however is incredibly dangerous, because unless it can freely escape upwards into the atmosphere and diffuse, it can be ignited by a very small energy ignition source and it ignites across a massive range of concentrations.
If you've ever worked or been anywhere where a hydrogen gas leak is possible, you will have seen the massive mitigation and control measures in place to try to prevent explosions as a result of a leak!
CoolHands said:
Did you lease the Hyundai? Can it be sent back as the result of no fuel supply? Imagine how much money Hyundai sunk into it to produce an engine etc that is basically defunct as the fuel supply is dead.
It is on a lease, shortly to reach term anyway.Tempted to buy it at an ultra low price
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