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At Last . . . .Some Hydrogen Sense


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Has anyone noticed this;

https://hydrogen-central.com/goodbye-e-cars-bmw-wants-mass-produce-hydrogen-cars/

 

https://discover.bmw.co.uk/article/step-inside-the-new-bmw-ix5-hydrogen

 

We have long needed a mass producer of cars, to commit to hydrogen, either cell or engine, in the face of the PC EV

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2 hours ago, Harbottle said:

Cars will weigh less too:D

You forget the lightweight aluminium or cardboard container for the hydrogen

That'll add weight 

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41 minutes ago, JohnG said:

You forget the lightweight aluminium or cardboard container for the hydrogen

Hmmmm - 700bar.   Might need some gaffer tape wrapped round it to beef it up...... 

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Hobson's choice: lithium battery fires or leaked hydrogen explosions. I would not park either close to the house, and certainly never in a garage.

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16 hours ago, Peter Cobbold said:

Hobson's choice: lithium battery fires or leaked hydrogen explosions. I would not park either close to the house, and certainly never in a garage.

Petter, I must admit that I find the general lack of confidence in Engineering depressing.

 

The idea of parking a leaking petrol driven vehicle in the stables, next to the horses, mirrors your thoughts on hydrogen.

We all know what petrol can do, look at the Buncefield fire

We all know what Hydrogen can do.

There are hydrogen powered cars, on long term trials in both the USA and Europe and both Toyota and Hyundai/Kia, offer hydrogen powered cars in their ranges.

 

Given that the expertise is there to build these cars and make them safe, why would we hark back to what are basically the same fears that our ancestors had about petrol?

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15 minutes ago, JohnG said:

The idea of parking a leaking petrol driven vehicle in the stables, next to the horses, mirrors your thoughts on hydrogen.

We all know what petrol can do, look at the Buncefield fire

We all know what Hydrogen can do.

Even a minor petrol leak is very noticeable by the smell but hydrogen is odourless so you wouldn't know.  On the other hand, petrol vapour is heavier than air and hangs around, whereas hydrogen will quickly disperse. 

Hydrogen is particularly dangerous as it is flammable at concentrations between 4% and 75% by volume in air which is a very wide range. Petrol vapour on the other hand will only burn when in concentrations between 1.2% and 8%.

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I remember chatting to Harold Roxbee Cox (Lord Kings Norton) who worked on the R101 airship back in the 1920's 1930's. I am not sure if it was the R101 or the Hindenburg but  luckily for him he gave up his seat to someone else on the very flight that the airship caught fire killing most of them on board. He witnessed the airship go up in flames knowing that he could easily have been on board. He was quite an interesting character. He used to turn up in a 6.3 litres V8 Bristol 411.  A beautiful car with a superb red leather interior. Look at the link to see detailed photos

Keith

https://www.classicdriver.com/en/car/bristol/411/1970/769805

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5 hours ago, RobH said:

Even a minor petrol leak is very noticeable by the smell but hydrogen is odourless so you wouldn't know.  On the other hand, petrol vapour is heavier than air and hangs around, whereas hydrogen will quickly disperse. 

Hydrogen is particularly dangerous as it is flammable at concentrations between 4% and 75% by volume in air which is a very wide range. Petrol vapour on the other hand will only burn when in concentrations between 1.2% and 8%.

I understand that Rob, my point was that I hope we, as a nation,  have move beyond the fear of what we cannot see.

Yes, hydrogen is dangerous, but so is much of our modern lives, including, as Peter so rightly points out, lithium car batteries

We don't fear the arrival of every day.

I just don't believe that it is beyond the wit of man, to store hydrogen safely onboard a car, lorry or train.

We do it with LPG

We do it with nuclear waste transportation containers, that are designed to survive a 40mph train crash

Somewhere between these two is a solution to safely store hydrogen, it just needs finding.

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On 7/29/2022 at 1:39 PM, RobH said:

Hmmmm - 700bar.   Might need some gaffer tape wrapped round it to beef it up...... 

Yeah, but quite commonly Diesel trucks inline pressure on the head line feed is...1600 bar ! nothing new with the numbers, just the product it's flowing.

Mick Richards

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5 hours ago, Motorsport Mickey said:

Diesel trucks inline pressure on the head line feed is...1600 bar ! nothing new with the numbers, just the product it's flowing.

Yes but those fuel lines are not storing compressed gas Mick.  Diesel is an incompressible liquid so the stored energy is minimal. 

The stored energy in 6 kg of gas at 700 bar is enormous - equivalent to a small bomb*. This is not the energy from combustion of the gas, it is the energy stored in it by the compression. 

 

 

Edited by RobH
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Just now, RobH said:

Yes but those fuel lines are not storing compressed gas Mick.  Diesel is an incompressible liquid so the stored energy is minimal. 

The stored energy in 6 litres of gas at 700 bar is enormous - equivalent to a small bomb. This is not the energy from combustion of the gas, it is the energy stored in it by the compression. 

Good point, well made.:o

Mick Richards

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Quote RobH, "Diesel is an incompressible liquid so the stored energy is minimal."

Water is an incompressible liquid, but have you never seen a water cutting machine?  At least nine INCHES of stainless steel, probably more, at one pass.   

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That isn't stored energy though John - that is continuous external energy supplied from a high-pressure pump, so not the same thing at all.  The water is just acting as a medium to transfer energy from the pump to the metal.  It is a LOT of energy concentrated in a small area though. :o

 

 

Edited by RobH
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In my post above  in reply to Mick I said the stored energy was similar to a small bomb. I was curious to know how big a bomb so I have just done a fag-packet calculation for that. 

The formula for energy stored in a compressed gas is [p1V/(γ-1)] [1-(p2/p1)^(γ-1)/γ] in litre-atmospheres

P1 and P2 are the stored pressure and atmospheric pressure respectively, in bars. V is the volume in litres and y is a constant of 1.4 for most gasses

Using the BMW figures, compressing 6kg of Hydrogen to 700 bar gives a volume of 104 litres. 

Using these numbers I get a stored energy of 154,044 litre-atmospheres which equals 15.6MegaJoules. 

Available equivalence tables give that as roughly the same as 3.7kg of TNT.

 Remember, that is just the stored energy from compressing the gas - nothing to do with burning the Hydrogen. 

 

The engineers must have taken this into account when designing the storage system and will have built-in a suitable safety margin but to me it is still a worrying factor.  Regular inspection and maintenance will be safety-critical and I wonder what the expected life is. One might be rather wary of buying a used car having such a system. 

 

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The ‘fibre glass’ tank manufacture that is used in Japanese CNG fuelled (compressed natural gas)  taxi cabs I saw in trial stage in a manufacturers in Banbury 20 years ago.  They were proving the manufacturing process before shipping the fully operational facility to Japan.   The tanks are made using continuous strand and resin on a what looks like a big bobbin winder.   
 

This is I think a similar item. https://www.mahytec.com/en/compressed-hydrogen-storage/

 

We did have hydrogen powered busses in London in 2010, in full use on one route in Boris’s days as London Mayor.  
https://www.londonreconnections.com/2021/the-second-coming-of-hydrogen-londons-hydrogen-buses/

Edited by BlueTR3A-5EKT
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Yes that is how it is described by BMW Peter -  the overwind is carbon fibre. Nothing new in that, as you say - the process has been in use for many years.  The difference here is the numbers that could be mass produced, and ensuring compliance with the maintenance regime that will be required to ensure long-term safety.  

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Firefighters use fibreglass tanks for their breathing masks (compressed air to approx 200 bar I think) Scuba tanks are steel or aluminium, & again ate rated at 200 or for some 250 bar. These have to be inspected & pressure tested regularly.

Bob

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17 hours ago, RobH said:

That isn't stored energy though John - that is continuous external energy supplied from a high-pressure pump, so not the same thing at all.  The water is just acting as a medium to transfer energy from the pump to the metal.  It is a LOT of energy concentrated in a small area though. :o

 

 

Ah, learn something every day!  Thanks, Rob.

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The problem is fundamental: the hydrogen molecule is the smallest of all molecules and can pass through all solids, even metals. Leakage through the wall of perfctly manufactured containers and hoses is inevitable. The allowable leakage rate is an important factor in safety as this review shows. Garages will need to have known airflow changes:

https://h2tools.org/sites/default/files/2019-08/paper_-_part_1.pdf

They briefly mention risk of hydrogen gas accumulating within the vehicle compartments.

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But hydrogen is just a means to transport and carry energy.     It must be generated, and sindar only tiny quantities of H2 are 'green', produced from renewable energy.  'Blue' H2 is made from fossil fuel energy, but with carbon capture and vastly the most H2 available today is 'Grey', just made from fossil fuel.

Clean fusion nuclear energy has been forty years away for the last fifty years.   It might just be a bit nearer if the ITER project works! See https://www.iter.org/

John

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...and in addition to the energy expended in generating the hydrogen in the first place, it also takes energy to compress it.  For the BMW example  of a 104 litre tank at 700 bar, even with circa 50% compressor efficiency it could take 9kWh of energy to compress the gas for each tank-full. 

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3 hours ago, RobH said:

...and in addition to the energy expended in generating the hydrogen in the first place, it also takes energy to compress it.  For the BMW example  of a 104 litre tank at 700 bar, even with circa 50% compressor efficiency it could take 9kWh of energy to compress the gas for each tank-full. 

Have we now hit the realm of PV panels? 
 Cost more In energy to produce and transport than they will make in their working life time.

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Production of hydrogen from methane using molten tin is still a live area of research. Carbon powder is waste and can be used as soil improver. https://www.internationaltin.org/more-scientists-produce-hydrogen-with-molten-tin/

But it needs green electrcity to power it, and the losses may be a snag.

 

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