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Comment by SigmundA | Hacker News Reader

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, while the Nexo advertises 380 miles vs 353 miles.

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.

Also fuel cell cars seem to use a buffer battery and have lower power output than BEV's as current fuel cells can't output as much burst power and can't store power from regenerative braking with out a battery somewhere.

Pretty skeptical about hydrogen fuel cells compared to the continued advancement in battery tech.

1.https://electrek.co/2018/05/27/tesla-model-3-range-new-hyper...

Edit: very good efficiency comparison of hydrogen vs batteries by Volkswagen, which to me shows the biggest issue with using hydrogen in cars the "well to wheel" efficiency:

https://www.volkswagenag.com/en/news/stories/2019/08/hydroge...

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> 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.

> 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.

I'm curious to know how you come to this conclusion? I don't know much about aerodynamics other than at, as a first order approximation, drag is proportional to the SQUARE of the velocity. Driving 887.5 km at an average speed of 66.9 km/h is, afaict, much more impressive than driving 975 km at 40 km/h.

Drag isn't the only thing in play. They both are driving below highway speeds, one more so than the other, I wish there was some data for a Tesla at 40 mph vs 25 or 48 to compare more directly the difference. The Tesla will have between 975 and 708km range at 40 mph the NEXO is 887km, I will make an assumption the Tesla is less, but how much less, is it "much" different?

What is the energy density delta between a HFCV and BEV currently?

Doesn't matter much. Below about 80km/h rolling resistance is dominant.

>What is the energy density delta between a HFCV and BEV currently?

Depends on what you're counting. Mirai's fuel cell stack, composite overwrapped tank, additional underbody and rear impact crash protection, high pressure filling system, cooling and fan intake system, and lithium battery together masses well over 400kg. Also takes up a lot of cabin and cargo space necessitating a larger vehicle.

Tesla's new 4680 batteries form part of the vehicle's structure and add free torsional rigidity, and will weigh roughly the same as a fuel system for 600km range. I imagine in the compact they'll package it into the unused area under the rear seat in order to drop the floor which should help with CdA.

>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 pressure tanks goes up with their surface area while the energy stores goes up with volume.

So for applications where you want to store a lot of energy and are weight but not volume limited, hydrogen might make enough sense to pay the efficiency penalty required to turn electricity into hydrogen and back again.

That's why it makes more sense for big trucks than it does for passenger cars where volume limitations matter a lot more and where total energy is less.

> 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

Nope, because you don't make hydrogen tanks out of materials that are susceptible to hydrogen embrittlement.

In particular, pressurized automotive-size hydrogen tanks aren't made from metal at all, they are typically epoxy/kevlar/carbon fiber composites.

OOC, since you know what these tanks are made out of, what is the duty cycle/lifespan of those tanks? I was presented some info on Kevlar tanks for drones using fuel cells and remember thinking that the lifespan was very short.

Anything bound by epoxy (or any polymer?) surely will have a comparably short lifespan...

Toyota certify and guarantee their tanks for 15 years, in production cars that you can go out and buy today.

Right you are!

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.

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?

Yes I always like to do my own math it has sniffed out the BS many a time from the likes of Tesla, Nikola and so on. Not always right, but amazing how many times theirs is wrong especially if marketing something.

You should alway try to understand the math / science and make your own judgements rather to falling for arguments from authority. This isn't always feasible but I think most people can do enough to weed out the snake oil to a much better degree than we seem to be doing as a society now.

Note this will also make you a better engineer / programmer in my experience.

Do you see Tesla as a snakeoil company today when it comes to their batteries, drivetrain, range, reliability? I wouldn't put Nikola and Tesla in the same categories. Tesla has one serious issue imho that they can only fix with refunds of the cost, that their auto-driving cars probably won't get there in the next 5+ years, so all the people that paid up to 10k for that will have to get some compensation.

No I don't however I was much more skeptical of them in the past and also the math still lets me know Elon's timelines are lets say "optimistic", however the math also told me they where not completely full of it vs Nikola which is a complete sham.

For instance the Semi being announced in 2017 I said no way, but their range numbers where not outlandish, they just conveniently left off weight numbers for the tractor and cost of the battery seemed to high at the time. What I missed was how quickly battery cost are coming down and energy density going up, however they still haven't delivered a tractor yet so...

Tesla has a real tech lead, not sure if they can keep it and they are way over valued stock wise.

Nikola complete BS.

The people on HN are the same people that work at Toshiba, Volvo and Daimler. Many of them are more accomplished and you'll find sub-par engineers making bad decisions at any company.

Math, physics, and chemistry, don't discriminate.

The Emperor and the downtrodden, the Ivey League and the community college, you'll find the same mathematics wherever you go.

Some may have an advantage in innovation or inspiration, but it should he fair trivial for any sufficiently motivated individual to check the numbers.

The companies are not entirely worried about the total results as they have other aspects to deal with (in fact, you'll sometimes find companies doing things they personally think are silly because "everyone" in the industry is doing it, and they need to be able to check off the box for the Board - example: "Why aren't we doing anything with this blockchain stuff").

They also have large resources and are willing to experiment in things (especially if there are incentives around it from government, etc) - and even if it fails entirely they'll likely get useful and actionable data and results that still can help the company.

Smart engineers chose Hydrogen as the first stage fuel fuel the Space Shuttle, and it turned out to be a terrible choice.

H2 offered the highest ISP, ie energy per fuel mass, and originally they wanted the Shuttle to be a single stage to orbit vehicle. But Hydrogen also added larger, much heavier tanks and engines didn’t have enough thrust for that. So they had to add large Solid Rocket Boosters to get off the pad. And all they additional dry mass meant the higher ISP of H2 was wasted.

And now the SLS is repeating those mistakes, not because engineers didn’t learn those lessons, but because politicians require them to repeat them.

Engineers recommending Hydrogen for cars are influenced by regulatory requirements and benefits, and politically by company objectives. If your CEO says Hydrogen is important to use because our government and regulators say it is, you as an engineer will find a way to make the best of a bad choice.

I have no horse in this race, but the pros and cons of a technology that is aiming to replace an incumbent that has lasted a century across the globe with millions (billions?) of users and units produced have to be evaluated as a complete system and in many more ways than pure engineering calculations. Fuel production, distribution networks, behavioural science, town planning, etc. were of little to no interest to the scientists you deride, but need to be considered too.

I once called BS on a VR article written by John Carmack on HN and he clarified the article. https://news.ycombinator.com/item?id=17348638

Which umm shows you never know who’s posting here.

You'll be surprised how much your predictions improve if you stop for a moment to do some back of the napkin calculations. Lots of overly optimistic or pessimistic news out there just to grab your attention. Having an edge in prediction and BS detection compared to the average Joe is an important life skill IMO.

> So for applications where you want to store a lot of energy and are weight but not volume limited, hydrogen might make enough sense to pay the efficiency penalty required to turn electricity into hydrogen and back again.

It's also not inconceivable that if we have more base load power generation (e.g. through more nuclear) then we could generate hydrogen at night with the excess.

For trucks and other heavy duty applications, liquid hydrogen starts to win out over pressurized. In LH2 tanks, the scaling becomes advantageous as you are optimizing against heat ingress, which goes down as 1/R when you increase the radius R.

Double walled high vacuum tanks that vent hydrogen gas if left unused for less than day and empty themselves after 10 days.

Liquid hydrogen at -253c that is more energy intensive to make than high pressure.

Not sure I see that being practical.

This information is just wrong. Air Liquide built automotive size LH2 tanks using multilayer insulation in the early 2000s that had 3 days of autonomy (time before first venting) and 3% per day boil-off after that.

For trucks where you need bigger tanks, both autonomy and boil-off rate improve by themselves due to the square-cube-law. And you can use the boil-off to charge the batteries in your hybrid electric powertrain, run auxiliary systems etc.

The LH2 trucks currently under planning have sophisticated fuel management systems where the driver inputs where she will stop and for how long, and the truck will optimize LH2 consumption and battery SoC before arriving at the stop point.

As for LH2 versus compressed: do you actually know how energy demanding a hydrogen compression train is? Compressing a low molecular weight gas to 700 bar is just fundamentally inefficient.

At the scale required for mass adoption of hydrogen fuels, both compression and liquefaction are talking 6-8 kWh/kg. For comparison the energy content in hydrogen itself is 33 kWh/kg. So naturally there is great interest in recovering as much as possible of that work before consumption.

This is the BMW tank I got those figures from which looks to be manufactured by Air Liquide [1]:

"To stay a liquid, hydrogen must be cooled and maintained at cryogenic temperatures of, at warmest, −253 °C (20.1 K; −423.4 °F). When not using fuel, the Hydrogen 7’s hydrogen tank starts to warm and the hydrogen starts to vaporize. Once the tank’s internal pressure reaches 87 psi, at roughly 17 hours of non-use, the tank will safely vent the building pressure. Over 10–12 days, it will completely lose the contents of the tank because of this"

At that temperature even sloshing around adds enough energy to heat and cause venting much sooner another reason its not great for mobile use.

Looks like Air Liquide made a different one that you are quoting perhaps an improvement, still high vacuum double walled, so you lose all your fuel in a month instead, thats progress.

This shows liquefaction to be about twice as energy intensive as compression (1.3 vs 3.4 kWh/kg theoretical 6 vs 13 kWh/kg actual) [2] So please point me to better info.

1. https://en.wikipedia.org/wiki/BMW_Hydrogen_7

2. https://www.hydrogen.energy.gov/pdfs/9013_energy_requirement...

Hydrogen needs to be a game changer to command a redirection of investment and effort for consumer transportation.

Even if it offers 20% better range and some allegedly better refuel experience (H2 people keep handwaving that as "solved"), that wouldn't justify the gigantic infrastructure switchover cost.

Electric vehicles can use the grid. That's a massive advantage for infrastructure readiness and scalability, even if the current grid isn't ready for full EV consumer transportation.

EVs can use home solar as well. Easily scalable, adds redundancy and alleviates load to the grid.

H2 would need a huge buildout of hydrogen generators, transporters, refuelling. EVs are so far ahead of all of that.

By the time any significant H2 infrastructure was out there, it'd be 10 years even if they secured 100s of billions in financing yesterday.

In 10 years, the alternative energy / solar / home solar / grid / battery / storage economic proposition is likely to be 50% cheaper in real dollars, and possibly even better.

It's the same problem nuclear faces.

Sure, throw some money at places like aviation or maritime shipping.

But it's just distraction, because I think the oil industry knows that the hydrogen will come from natural gas for the foreseeable (10-40 years) with some "future switchover" to "green hydrogen".

Green hydrogen smacks of "clean coal". Granted the physics/engineering for it are a lot more realizable.

But everyone should see that for the shell game it is.

> But it's just distraction, because I think the oil industry knows that the hydrogen will come from natural gas for the foreseeable (10-40 years) with some "future switchover" to "green hydrogen".

Hydrogen was always a distraction. Fuel cells have been 10 years away from practicality since the 80s, and hydrogen production was only ever non-fossil-fuel-based in theory. It's 100% a smokescreen to protect fossil fuels.

Plus, unlike gas, the hydrogen is never directly burnt "in the engine", it's always converted to electricity first. A hydrogen car is always going to use EV motors (and batteries, because while denser, H2 doesn't yet have anything near the ability to supply power at high demand that current battery tech has) and have all the complexity of an EV, often without the convenience of grid charging (home charging) given much smaller batteries to compensate for the weight of the fuel cell and fuel.

Even the greatest H2 car is always just going to be a second class EV with "weird fuel needs".

Maybe that's where current hydrogen R&D is going, but it isn't inherently true.

https://en.wikipedia.org/wiki/Hydrogen_internal_combustion_e...

But now you're again limited by the low efficiency of ICE, the theoretical limits imposed by the carnot cycle...

Hydrogen makes much more sense for container ships, where electric batteries can't be made practical, but hydrogen storage can be scaled easily.

I agree also perhaps for grid scale storage

Or aluminium smelters.

Ammonia is a better fit for marine applications, as it doesn't require high pressure or cryo storage. It can also be produced using renewable energy, and is cheaper to transport.

One of the largest producers in the world (CF Industries in Louisiana) has committed to producing it using offshore wind, and renewables in general (and their terminals are located in geographic areas where there is already high penetration of renewables on the local grid).

https://www.cfindustries.com/globalassets/cf-industries/medi...

Cryo/pressurized storage isn't technically necessary for ships either. Liquid hydrogen with insulated storage works well enough. The key is evaporation rates. As long as the ship consumes fuel faster than it evaporates, there is no need to maintain pressurization.

In practice, some buffering pressurization may be necessary, but the scale of pressurization needs will be a lot lower than is required to store hydrogen long term.

And if the ship sinks I guess hydrogen pollutes less than oil ?

Sure, but it's not a big concern as it's not that common.

To the person who disagrees - compared to climate change, it's the least of our worries.

No oil spills beats a few oil spills - but these are not an Exxon Valdez sized event, and they don't really matter in the grand scheme of things.

Maybe ever so slightly acidifies water + escapes atmosphere; I don’t think there is real hydrogen spill pollution.

The hydrogen goes up. Most of it will be in space in an hour or two. Any that doesn't will react with atmospheric oxygen to produce water vapor.

By a lot, mostly. The liquid hydrogen eventually doesn't have enough pressure/cold enough temperature to stay liquid so it turns back to gas and most bubbles out of the water (with some of it reacting with Oxygen and becoming more water). It's possible if it were a "big enough" and "concentrated enough" spill it might briefly create anoxic zones where fish will die. https://en.wikipedia.org/wiki/Anoxic_waters (But humans and dumb algae accidentally do that "all the time" and the ocean does have recovery methods from anoxic waters. It's not great for the climate or the ocean, but it is mostly survivable and much more "temporary" problem than the long term effects of oil pollution.)

It is also a greenhouse gas http://agage.mit.edu/publications/global-environmental-impac...

"If a global hydrogen economy replaced the current fossil fuel-based energy system and exhibited a leakage rate of 1%, then it would produce a climate impact of 0.6% of the current fossil fuel based system. "

That doesn't sound so ... bad?

And a Hyundai Kona Electric did 1000km as well, probably at ridiculously low speeds as well :) ( https://thedriven.io/2020/08/14/three-unmodified-kona-electr... )

> The results of the test – conducted over 3 days with three vehicles in Germany in conditions mimicking heavy urban traffic – are impressive for the Hyundai Kona Electric which is already one of the longest range vehicles on the Australian market.

Wow, it must have been brutal to drive 1,000km under faux heavy urban conditions.

The one thing H has going is quicker fills at the pump, right?

Being low on joules is a pain when you're going to work in the morning, but it's a royal pain if you have to wait a half hour to charge.

Yep if you have a hydrogen pump nearby it will probably fill faster than a charger. Not sure if they need attendants like a propane fill.

If you have a plug at home though thats much more convient at least to me when going to work.

You do not need an attendant the hydrogen stations I’ve been to.

At least you get a half hour to think about how you should have plugged it in last night.

For me that'd be half an hour to ruminate on how my apartment has no place to charge a car.

I am not getting an EV anytime soon unfortunately.

The general lack of EVs in multifamily housing is concerning for EV adoption - the only places where it's really possible is if the community offers a garage and the site's willing to book an electrician to install the 240v outlet.

I am fortunate that my building committee is pretty forward looking. It helps that many owners actually live there.

But it is a significant project and it doesn't look like EV charging standards (plugs, power delivery) are set across all manufacturers.

The balance of effort+money vs benefit/risk means we will keep driving what we know for now.

I know the tide will turn sometime, but not anytime soon.

30 mins at a supercharger is hundreds of miles of range...that's quite the commute. But if you're at home - yes, I guess not having any charge is an inconvenience in the morning, but so is not having any gas or hydrogen. Neither should happen if you are even remotely responsible and on top of your life.

On the other hand, if we ever build out electrified road infrastructure, one might be able to recharge a battery electric vehicle without even stopping just by pulling power from rails embedded in the road or overhead power lines.

Even there it's not a clear-cut victory.

The last time I looked at it, it turned out that hydrogen filling stations need a significant time after fueling each car to get back to transfer pressure. If you want to fill your tank right after someone else, you'll have to wait for a bit.

But overall, filling time is not that big of a deal. Most people don't really drive that much, and the car spends the majority of its time in a parking lot. In practice it turns out that just charging it at home every day is more than enough to keep a battery full.

In addition to that, commercial vehicles often have a driving time limit. As long as the recharge period is shorter than the mandatory break, you are not going to care about the recharge speed.

And both battery capacity and charging speed are quickly improving. There might be a small niche for hydrogen, but it's disappearing rapidly.

Unless your work is 300km away, that’s not true. Two minutes = 50km at a supercharger, and for that use you can slow charge at home.

The Nexo is much less aerodynamic than the Model 3. One is an SUV/CUV, the other is a low sedan which looks like wet poop. The Nexo has more frontal area and a higher CD. And the Tesla is known for rigging its EPA tests for higher, but illusory, numbers.

I own a model 3 and I laughed pretty hard at your comment regarding it looking like wet poop.

Ok so go to the Model Y which is slightly heavier (Actually closer to the Nexo) and the worse aerodynamics than the Model 3 should have minimal effect if hypermiling at low speed, which also helps the Nexo vs Model 3.

Model Y will blow the doors off the Nexo in performance due to much larger electric motors.

Pretty much everything is aerodynamic at 25mph when comparing to something else at 40mph...

> And the Tesla is known for rigging its EPA tests for higher, but illusory, numbers.

By that you must mean Tesla bothers to do the full suite of EPA tests instead of accepting a somewhat penalizing multiplier, like how other manufacturers do?

There's no rigging whatsoever and the same option is available for other manufacturers as well. If they bother to do the longer and more demanding test cycle, that is.

Nobody cares exactly how a company gets unrealistically high numbers. What matters is as a consumer your experience won’t match the company’s claims. Best would be for companies just to tell the truth. C.f. the “full self driving” falsehood.

Anyone who has bought a car in the last 50 years is already well aware of how much EPA mileage differs from actual mileage.

My old 2010 Prius was EPA-rated for 50 MPG. If I drove it with kid gloves over flat terrain, I could hit that mileage. If I drove it in a way that doesn't piss other road users off, I would get closer to 46 MPG.

If I was doing 80+ MPH over the Rockies on the Trans-Canada, I'd be getting a cool 35 MPG, because air resistance is very high at those speeds, and because most of my braking was exceeding the regenerative capacity of the car.

> Tesla is known for rigging its EPA tests for higher, but illusory, numbers.

The Tesla numbers are correct and verifiable, actually. The problem is that the EPA "highway" test is designed to capture the "average highway mile" driven by a US vehicle (which makes sense, it was designed to inform purchasers of aggregate fuel use). Here's the driving schedule:

https://www.epa.gov/sites/production/files/2015-10/hwfetdds....

Note that it never goes above 60mph, and spends most of its time between 40 and 50. This isn't wrong, but it corresponds to an urban highway commute (again, which is pretty much the "average highway mile").

The problem is that this does NOT match what typical consumers think of as "highway driving", meaning blasting 75mph+ down an open road. So people get in their Model 3's and measure their consumption at those speeds and it doesn't match.

And it's true that other EV manufacturers (Ford, especially -- the Mach E actually does somewhat better than sticker consumption on the highway) chose not to run the full test and used other methods that put a higher number on their stickers. And in context that's probably more informative.

But nothing was "rigged". In fact Teslas in stop-and-go urban commute traffic really do get close to their sticker mileage. It's just that no one cares because one's battery doesn't run out on an urban commute before you get home to charge it. Ironically, EV owners in this case care LESS about efficiency than gas owners.

> The Tesla numbers are correct and verifiable

There are caveats. The lower end Model 3s hit their estimates pretty reliably. The Performance trim usually misses by a pretty big margin for most people. There are exceptions to every rule, but I owned a P3D and hung out with other P3D owners as well, and this was a commonly shared experience.

I have to wonder how much of that is down to the way the driving habits of people who buy a car labeled "long range" differ from those who buy one that calls itself "performance". It doesn't really refute the notion that the difference between measured and claimed performance is due to the different driving conditions being tested.

IIRC there was some youtube video a year or two back that tested a few variants on a track using what they claimed to be a replica of the EPA highway test, and the cars came out almost dead on.

AFAIK, Tesla uses the same range estimate for all trim levels of the Model 3 (or did in 2019, at least). The problem is that the Performance trim has 20 inch non-aero wheels and sticky tires. I got 325+ Wh/mi steady state cruise on the highway using AP to do the driving (in good weather; was 350+ when colder).

There have been some independent tests and IIRC the consensus is that the standard range Model 3 was rated pretty accurately, and the Performance trim was rated something like 25-30 miles too high compared to reality.

The current site lists the LR at 353 miles EPA range and the performance at 315.

But again, you're using the words "on the highway" to reflect what I assume to be your driving habits in rural open road conditions and not the test that was actually performed to produce the numbers in the product specs. And that was my point. It's not about advertising fidelity at all, it's about regulation and its mismatch with the expectations of a modern EV driver.

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