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Hyundai Nexo sets new world record 887.5 km travelled on single tank of hydrogen

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Re: Hyundai Nexo sets new world record 887.5 km travelled on single tank of hydrogen

#261

Post by hydrogtehd »

goodpoint wrote: post #181
baybal2 wrote: post #166

Earlier quoted context omitted.

How many people would be ready to drive a hydrogen bomb?

More than a gasoline bomb, hopefully. Gasoline is more dangerous.

No, it isn’t. Gasoline is dangerous, but it’s a liquid. H2 is a gas, under extreme pressure, and with a very low spark energy.

The spark (ignition) energy is very important safety wise. Nothing will light without an ignition source. In fact hydrogen is more dangerous wrt to gasoline than gasoline is wrt to flour (yes, flour can explode). That is:

Flour:gasoline Hydrogen is dangerous. And that’s fine.

[1] http://www.explosionsolutions.co.uk/110411020.pdf

Re: Hyundai Nexo sets new world record 887.5 km travelled on single tank of hydrogen

#262

Post by jandrese »

MayeulC wrote: post #213
baybal2 wrote: post #192

Earlier quoted context omitted.

Few kg of hydrogen are surely more dangerous than 50 kg of gasoline.

120 MJ/kg for H2 vs 46 MJ/kg for gasoline. Both are explosive, so I think (I'm no authority on this) we can compare those values directly, without taking into account the storage pressure. Source: https://hypertextbook.com/facts/2005/MichelleFung.shtml https://hypertextbook.com/facts/2003/ArthurGolnik.shtml

Gasoline will not explode in normal conditions. Even in an accident it is pretty safe, although the risk of fire must always be considered.

A 10k PSI H2 tank is a straight up bomb. A gasoline tank can start a nasty fire but nobody is going to be torn apart by shrapnel or killed by the overpressure wave in an accident. Gasoline cars don't explode like they do in the movies. It must also be noted that the large batteries in EVs are also a fire hazard and in some ways worse than gasoline. For gasoline to act like a bomb it has to be aerosolized first and then ignited. In an accident there's not much that could achieve that. With a high pressure H2 tank something that cracked it open and allowed all of the H2 to be released at once would instantly create the conditions for a massive explosion. All it would need is a single spark.

Re: Hyundai Nexo sets new world record 887.5 km travelled on single tank of hydrogen

#263

Post by donkeyd »

hwillis wrote: post #138
contriban wrote: post #52

Earlier quoted context omitted.

> anyone could trivially break the record "Make it bigger" doesn't really work in cars, otherwise range anxiety wouldn't exist as a concept. The record still makes sense because the Hyundai Nexo is commercially available and it's not a prototype with a comically-large just for the record tank.

While it's true that you could add probably double the H2 storage to most HFC vehicles, I think this is the correct take. The Mirai's fuel tank is 37.25 gallons/141 liters vs 12-15 gallons/45-55 liters of gasoline for most cars. Tank capacity only helps so much. You may have to fill up half as often, but having to go out of your way for a special station is annoying. ICE vehicles could easily have 40 gallon tanks, an…

> but having to go out of your way for a special station is annoying

I went back from a Tesla to a diesel car. I hate going out of my way to special stations to fill up my car with diesel. I much preferred unplugging in the morning and plugging back in in the evening.

Re: Hyundai Nexo sets new world record 887.5 km travelled on single tank of hydrogen

#264

Post by jandrese »

giantg2 wrote: post #132
tyingq wrote: post #99

Earlier quoted context omitted.

Long fill times? This commercially available one says 48 hours to re-charge it. https://www.fuelcellstore.com/hydrogen-equipment/hydrogen-st...

Yeah, but ideally they'd be swappable. Similar to propane tank exchanges. Or even how some EVs were thinking about battery swap stations.

Aren't they really heavy? This is also why swappable batteries in EVs never got off of the ground. You need a crane to do it and that's too much effort for a top-up.

Re: Hyundai Nexo sets new world record 887.5 km travelled on single tank of hydrogen

#265

Post by trutannus »

_gtly wrote: post #248
trutannus wrote: post #84

Earlier quoted context omitted.

Same question from me also. Also, hydrogen is highly explosive, so how can that be safely used in cars without detonating a la Hindenburg whenever there's a collision?

The danger of using hydrogen gas in a vehicle may be on the same order as compressed natural gas (CNG) which is used for e.g.: some busses. Hydrogen is stored under very high pressure in tanks, which if ruptured in an accident can cause a physical explosion. A study on CNG in busses says: "One can therefore conclude that CNG buses are more prone to fire fatality risk by 2.5 times that of diesel buses, with the bus pa…

> 2.5 times that of diesel buses

These are not compelling numbers. Ideally you'd want something safer, not a few times more dangerous.

Re: Hyundai Nexo sets new world record 887.5 km travelled on single tank of hydrogen

#266

Post by hydrogtehd »

NikolaNovak wrote: post #116
KMnO4 wrote: post #12

Since “tank” isn’t a unit of measure, I suppose anyone could trivially break the record with a larger tank. From the article: > The Nexo consumed 6.27kg of H2 For comparison with the other production H2 cars: Toyota Mirai: 5.6kg Honda Clarity: 5.0kg Seems like a promising technology. My understanding is that the current blocker is infrastructure. It’s hard to pressurize up to 10,000 PSI, so many facilities are only a…

Gack... one of my pet peeves: 90% of my friends compare car millage in terms of "how much money I spend to refuel", completely ignoring: 1. Significantly different tank sizes - 53L to 70L on regular cars. 2. Different prices of gas (suburbs vs downtown, 87 vs 91 octane, etc) 3. Different habits - some refuel at 1/3 left, 1/4 left, 50km left, yellow light on, needle at the end of the gauge, etc It drives me absolutely…

You might have poor friends who have cash flow problems. When I was a kid my parents wouldn’t fill up the tank, they’d put L20 000 in it ($15). About half way up. They couldn’t afford more.

For people like this, how much the car costs per stop is important. Especially if a re-fueling typically occurs after the next pay period.

Re: Hyundai Nexo sets new world record 887.5 km travelled on single tank of hydrogen

#267

Post by fouric »

bdamm wrote: post #92
sandworm101 wrote: post #66

Earlier quoted context omitted.

It is, but it doesn't have to be. It is possible to make H2 from H20 and sunlight. At the moment there is little market for such "green" hydrogen but the hope is that hydrogen-based transportation will create that market. Imho I cannot afford to be a market leaders in this field. Until H2 is available everywhere, including at remote locations during Canadian winters, I'll have to stick to gas stations. (I have yet to…

While technically true, the conversion is inefficient. It takes a lot of power to extract H2 from H2O. You could just use that power directly. The problem with electrics in -50 is keeping them plugged in when not in use. -50 is very extreme though, you’re talking far north or Edmonton.

> the conversion is inefficient. It takes a lot of power to extract H2 from H2O.

How inefficient? That number matters. If it takes 500 kWh to make a tank that stores 100 kWh, you'd be a fool to use that energy directly, as that tank is going to store hundreds of times that much (at least) over its lifetime.

Re: Hyundai Nexo sets new world record 887.5 km travelled on single tank of hydrogen

#268

Post by SigmundA »

Mvandenbergh wrote: post #244
SigmundA wrote: post #117

This is at 66.9 km/h (40 mph) in order to greatly increase its range due to lower drag compared to normal highway speeds. As a comparison a Tesla Model 3 got 975km (606 miles) at 40 km/h (25 mph) [1]. I can't seem to find any range tests at a similar speed as the Nexo. I found an EPA dyno test for the Model 3 at 77 km/h (48mph) for 708 km (440 miles). The Nexo and Model 3 have similar dimension and weight and price,…

>It doesn't seem like current fuels cell have much of a energy density / range advantage even though hydrogen itself is much more energy dense, the fuel cell weight and efficiency and high pressure liquid hydrogen tanks must be accounted for. Hydrogen has a better gravimetric scaling than batteries - as stored energy increases, the fixed weight of the fuel cell is amortised over more energy and the weight of high pre…

Lithium batteries still seem to have a way to go in energy density currently at around 250-300 wh/kg and going up year over year with a theoretical maximum (Sulfur cathode) of above 2500 wh/kg.

At around 2000 wh/kg you are equivalent to diesel drivetrain energy density both size and weight based on my rough math.

Expensive large hydrogen tanks in a trailer with high pressure lines to tractor seems like it would cause safety and cost issues offsetting much of the benefit.

Re: Hyundai Nexo sets new world record 887.5 km travelled on single tank of hydrogen

#269

Post by jbarberu »

marvin wrote: post #253
jbarberu wrote: post #215

Earlier quoted context omitted.

When you go in neutral downhill your engine idles, vs if you leave it in gear the ECU cuts fuel supply completely. It's generally better to stay in gear except when you're at a standstill. (This assumes a modern vehicle with fuel-injectors)

Do automatic gearboxes compression brake when going downhill? That's what I was trying to avoid. My point was to conserve your kinetic energy, not optimizing the fuel flow during the times when you don't want the engine to produce power.

Can't speak for all of them, but many will engine brake if you use cruise control downhill.

Re: Hyundai Nexo sets new world record 887.5 km travelled on single tank of hydrogen

#270

Post by jandrese »

SigmundA wrote: post #197
onychomys wrote: post #64

Earlier quoted context omitted.

Presumably it'll eventually be made by splitting water using electricity from renewable sources.

Splitting water with electricity then recombining in the fuel cell back to electricity is extremely inefficient compared to just charging a battery with eletricity.

It may make sense in cases where batteries aren't practical like ocean going container ships.

There was a time a couple of decades ago when it might have made sense for cars when battery power wasn't good enough but that time has passed.

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