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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

#271

Post by eulers_secret »

mastazi wrote: post #69
cogman10 wrote: post #26

Earlier quoted context omitted.

Here a few major issues hydrogen would need to solve. * There isn't a fuel distribution system. The reason BEVs work is because everywhere has power, setting up power distribution is generally just plugging into the local grid. * Hydrogen escapes any container it's placed in. That's a pretty hard thing to deal with. Most approaches have looked at chemically binding hydrogen to something in order to keep it from escap…

> You can get a lot more miles out of the basic combustion engine design Why would there be a combustion engine in a hydrogen car? I expect that there would be a fuel cell powering electric motors. Are there other ways to use hydrogen in cars, other than fuel cell? I'm not an expert.

You can use hydrogen in a modified combustion engine: https://en.wikipedia.org/wiki/Hydrogen_internal_combustion_e...

Doesn't look like a great path forward - deep internal engine parts need to be modified (no "hydrogen kit" for existing cars), they emit NOx emissions (so not zero-emission), and you have all the disadvantages of a combustion engine.

However, combustion engines have 100 years of development behind them and a proven track record of reliability (probably billions of running hours by now). Fuel cells are still newish - "the devil you know". This would also keep mechanics employed and keep dealership service bays busy... kind of a perverse incentive, but it's there for sure.

It may be a stop-gap, or useful for certain situations (long haul trucking is mentioned). It could be part of the tapestry of technologies needed to move to a more renewable-based future.

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

#272

Post by m4rtink »

jacquesm wrote: post #232
HPsquared wrote: post #207

Earlier quoted context omitted.

Even worse than simply leaking, hydrogen can diffuse into the crystal structure of metals and cause havoc with the material properties. It's definitely not as friendly as hydraulic oil.

Exactly. This is a major problem with anything hydrogen related, especially if it has an expected lifespan of a decade+.

And once it gets the thing all brittle and it starts leaking, you won't see it burn as it produces a lot of IR but almost no visible light.

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

#273

Post by abakker »

eternauta3k wrote: post #259
Mvandenbergh wrote: post #244

Earlier quoted context omitted.

>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…

> the weight of high pressure tanks goes up with their surface area while the energy stores goes up with volume. Nope, tank mass scales with volume because bigger tanks need thicker walls: https://en.wikipedia.org/wiki/Pressure_vessel#Scaling

With hydrogen this is especially problematic due to hydrogen embrittlement. https://en.wikipedia.org/wiki/Hydrogen_embrittlement

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

#274

Post by arcticbull »

Correct me if I'm wrong, but isn't the issue with hydrogen the supply chain? I believe the overwhelming majority of hydrogen is currently produced from fossil fuels.

> As of 2020, the majority of hydrogen (∼95%) is produced from fossil fuels by steam reforming of natural gas, partial oxidation of methane, and coal gasification. [1]

[1] https://en.wikipedia.org/wiki/Hydrogen_production

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

#275

Post by daniellarusso »

arcticbull wrote: post #274

Correct me if I'm wrong, but isn't the issue with hydrogen the supply chain? I believe the overwhelming majority of hydrogen is currently produced from fossil fuels. > As of 2020, the majority of hydrogen (∼95%) is produced from fossil fuels by steam reforming of natural gas, partial oxidation of methane, and coal gasification. [1] [1] https://en.wikipedia.org/wiki/Hydrogen_production

How viable is it to extract from water via solar power?

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

#276

Post by labcomputer »

darksaints wrote: post #240
labcomputer wrote: post #236

Earlier quoted context omitted.

That analysis ignores the heat used to raise the reactant (water) temperature to 800C. On its face, the claim doesn't make much sense anyway. If you could convert water to 2 H2 + O2 at zero energy cost, you could make a perpetual motion machine by taking advantage of the exothermic reaction 2 H2 + O2 -> 2 H2O.

That's the difference between LHV and HHV. It is possible to exceed 100% efficiency when using HHV because it is an inherently more conservative convention for energy content due to practical concerns. LHV, by contrast, is bounded by the laws of physics.

Well, no, that's still wrong. The >100% efficiency comes from using two slights of hand:

1. Counting only the electrical energy input. But you also need to supply heat at the same time. That's the whole point of this product--use heat ~~instead of~~ (edit: in addition to) electricity to split water.

Critically, they are assuming you get "free" (as in beer) waste heat at 800C... which is fairly silly. 800C heat is high-grade energy, not waste heat. Exhaust gas from a combined-cycle NG power plant, for example, is more like 250-300C. Thermal steam plants operate with a Th of ~550C (so the waste heat is much, much cooler).

2. Ignoring the fact that you need to heat the reactant (water) to 800C before you can have the discussion in #1. Now, the problem is that the heat capacity of water is much higher than an equal mass of H2 and O2. So, you can't even use the hot as-produced gas to heat the incoming water to anywhere near the operating temperature of the electrolyzer.

The efficiency in a practical application is probably half to two-thirds of what they are claiming.

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

#277

Post by emptyfile »

SigmundA wrote: post #268
Mvandenbergh wrote: post #244

Earlier quoted context omitted.

>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…

I have no clue about batteries or hydrogen tanks.

But I'm always amused to think that posters on HN give more credence to their back-of-the-napkin calculations over opinions of, say, folks at Toshiba, Volvo or Daimler.

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

#278

Post by toast0 »

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…

Feels like the infrastructure and on car issues are going to be similar to CNG, but worse. Need new fuel stations, high pressure storage, no existing delivery network (worse than CNG; although CNG pipelines are much lower pressure than vehicles need, so you needed a compressor at the fueling point); and the killer --- the vehicle tanks expire and replacement may not be economically feasible, in which case your car's value evaporates when the tank expires (generally 15 years after tank manufacture); this is what happened to most CNG cars.

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

#280

Post by daniellarusso »

emptyfile wrote: post #277
SigmundA wrote: post #268

Earlier quoted context omitted.

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…

I have no clue about batteries or hydrogen tanks. But I'm always amused to think that posters on HN give more credence to their back-of-the-napkin calculations over opinions of, say, folks at Toshiba, Volvo or Daimler.

Are these humans mutually exclusive?
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