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Why do transit agencies keep falling for the hydrogen bus myth?

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Re: Why do transit agencies keep falling for the hydrogen bus myth?

#91

Post by avidiax »

WalterBright wrote: post #8

The electric airplane is another myth. There is no known battery technology, or one on the horizon, that can provide a large enough power/weight to make them practical. The investors are getting bilked.

I feel there is an unaddressed market for a hybrid gas/electric or diesel/electric powerplant.

Size the battery for takeoff/climbing/go-around/diversion use-cases. Size the fossil-fuel engine for cruising power, which should improve efficiency. During takeoff and climbing power, the two motors work together. During cruise and descent, the electric motor regenerates the battery. I imagine that for general aviation, you would maintain one propshaft and not even bother with a clutch pack, since the gas engine is needed in all phases of flight, and freewheeling an electric motor is simple. Perhaps have the fossil-fuel engine keyed to the shaft with a shearing pin, so that if the engine seizes, the electric motor still turns the prop.

This has the advantage that you now have two independent motors, which could eventually help with ETOPS rating, but would initially improve safety/reliability for general aviation.

Yes, you are still fossil-fuel dependent, but you burn much less of it, first by offsetting some takeoff energy to the electrical grid, and secondly by reducing reserve power in the fossil fuel engine to improve efficiency.

Re: Why do transit agencies keep falling for the hydrogen bus myth?

#92

Post by bolognafairy »

adrian_b wrote: post #49
bobthepanda wrote: post #21

Earlier quoted context omitted.

This depends a lot on local climate and topography. Seattle has kind of been a bust with them because the hills really reduce the amount of charge, and on top of that the existing bus depots are already full, so switching to electric only would mean having to find and locate space for more bus depots, which is quite difficult.

Hills should never reduce the range, because the energy lost during climbing up is recovered when going downhill. This is one of the great advantages of electric vehicles with batteries, when properly designed. Electric buses with batteries are even more suitable for cities with hills than for cities without hills, because they provide greater energy savings over buses with ICEs. While I have never used buses with ba…

This is a weird multi-paragraph evangelical lecture seeing as any EV owner that’s driven in a hilly climate will tell you that this isn’t how things work.

Regen isn’t 100% efficient, for starters.

Re: Why do transit agencies keep falling for the hydrogen bus myth?

#93

Post by bolognafairy »

bluGill wrote: post #66
abdullahkhalids wrote: post #47

Earlier quoted context omitted.

Many bus routes have a 5-10ish min break at some point (usually the main station) in the route. If you can utilize those ten minutes to do a top-up, you can go a lot further on the same sized battery.

No bus route should be more than 15 minutes between full and empty. That is you start at some station, go 15 minutes, then turn around and go back. There are many systems that attempt to do more, but there is no point: people have places to be: on the bus is not on that list. That 15 minutes means an average of 7 minutes, now they walk to some other express bus that gets them nonstop (at faster speeds) to someplace,…

Sorry, but, what the hell? This is Hacker News at its finest: completely talking out of its ass.

This isn’t how bus routes work, and this isn’t how people ride busses, on most if not all of the…many PT systems I’ve used in multiple states / countries.

Re: Why do transit agencies keep falling for the hydrogen bus myth?

#94

Post by bolognafairy »

cf100clunk wrote: post #39

Look into propane (a.k.a. LPG or Autogas). If the goal is anything-but-diesel-or-gasoline/petrol, the use of propane (a fossil fuel that is a byproduct of oil and gas refining) is a well-understood, well-implemented practice. I am not advocating for propane as a primary solution, but rather as part of the journey towards truly clean vehicle emissions and the ramp-down of heavily polluting fossil fuel refining. Propan…

I tell you hwat!

Re: Why do transit agencies keep falling for the hydrogen bus myth?

#95

Post by hatthew »

hannob wrote: post #61
hatthew wrote: post #55

> Fuel cell buses do produce sufficient waste heat, but here’s the problem: it’s exceptionally expensive heat. Every degree of warmth comes from hydrogen — a fuel that’s costly to produce, store, and transport. Unlike diesel, heating with hydrogen’s waste heat is technically easy but economically painful. Isn't waste heat pretty much free by definition?

Within one technology, that'd be true. But not if you have the option to choose another technology that produces a lot less waste heat.

Yeah, I just find the framing very weird. It's talked about as if it's somehow worse than diesel. But then isn't the issue that hydrogen fuel is less economical than diesel in general, regardless of whether the fuel is used for locomotion or for passenger heating? In the context of passenger heating specifically, waste heat is either free for both diesel and hydrogen, or equally non-free for both.

Also the article appears to be arguing for electric instead of hydrogen buses, but for some reason seems to try to frame "winter range" as being an issue for hydrogen buses specifically, and then says "electric buses face a different challenge" -- winter range.

I feel like there are two separate points that can be made:

- Hydrogen fuel is more costly than diesel or electric (not even sure how true this is, but it's what the article seems to indirectly imply).

- Hydrogen fuel doesn't have winter range issues the way electric buses do, but regardless electric is still better for other reasons.

Re: Why do transit agencies keep falling for the hydrogen bus myth?

#96

Post by AnthonyMouse »

jshier wrote: post #32
mschuster91 wrote: post #25

Earlier quoted context omitted.

> The ideal drivetrain was invented over 20 years ago by Toyota and apparently nobody but me and Honda noticed it! The problem is hybrid drivetrains are complex . You don't save anything on the complexity of a combustion engine and exhaust train (over 1000 individual parts that have to be machined at extremely low tolerances), but add a more complex transmission (it needs to be able to work with two distinct inputs)…

As a simple driver of cars, I've never understood why no one has mass produced an EV with a built-in generator. That would avoid the complexity of the hybrid drive train, allow easy plugin and short range electric-only travel, and could even be offered as an optional attachment. So what am I missing? Is the efficiency gained by the generator offset by losses through the EV system?

That is called a series hybrid and the reason they're not popular is that the power split device in common hybrids is simply better.

The power split device isn't an ordinary transmission, it's a set of planetary gears with a fixed gear ratio between three shafts. One goes to the wheels, the other two to the engine and the electric motor respectively. The ratio of the engine speed to the wheel speed is then set by the speed of the electric motor connected to the third shaft, which gives you a CVT with no belts, clutches, torque converters or even synchros.

The transmission is "more complicated" only in the sense that it contains electric motors. In every other respect it's simpler, more efficient and more reliable than an ordinary transmission. Meanwhile those electric motors mean you don't need a starter motor or an alternator because the engine can be started by the electric motor through the transmission and an electric motor is a generator when operated in reverse.

A series hybrid still requires you to have a gas engine with all that entails, but now the gas engine needs its own dedicated electric generator/motor and you can't deliver power from the gas engine directly to the wheels, so the traction motors have to be bigger in order to supply 100% of the torque used in acceleration instead of the gas engine and electric motors both contributing. That makes series hybrids heavier, slower and more expensive, so they're basically useless. Probably the main advantage would be that you could offer the generator as an option on what would otherwise be a full electric vehicle and then only people who need the extra range would pay for it.

Re: Why do transit agencies keep falling for the hydrogen bus myth?

#97

Post by bluGill »

thfuran wrote: post #86
bluGill wrote: post #66

Earlier quoted context omitted.

No bus route should be more than 15 minutes between full and empty. That is you start at some station, go 15 minutes, then turn around and go back. There are many systems that attempt to do more, but there is no point: people have places to be: on the bus is not on that list. That 15 minutes means an average of 7 minutes, now they walk to some other express bus that gets them nonstop (at faster speeds) to someplace,…

Is there any bus route anywhere that never goes more than 15 minutes from the depot?

Not that I know of - but there shouldn't be.

Re: Why do transit agencies keep falling for the hydrogen bus myth?

#98

Post by bluGill »

bolognafairy wrote: post #93
bluGill wrote: post #66

Earlier quoted context omitted.

No bus route should be more than 15 minutes between full and empty. That is you start at some station, go 15 minutes, then turn around and go back. There are many systems that attempt to do more, but there is no point: people have places to be: on the bus is not on that list. That 15 minutes means an average of 7 minutes, now they walk to some other express bus that gets them nonstop (at faster speeds) to someplace,…

Sorry, but, what the hell? This is Hacker News at its finest: completely talking out of its ass. This isn’t how bus routes work, and this isn’t how people ride busses, on most if not all of the…many PT systems I’ve used in multiple states / countries.

There is a reason people complain about buses and prefer to drive in so many cases. Operators try to compromise on cheap and end up with service for those who after 5 DWIs can't get their friends to drive them anymore.

Re: Why do transit agencies keep falling for the hydrogen bus myth?

#99

Post by ttttannenbaum »

PaulHoule wrote: post #75
rsynnott wrote: post #6

Huh. I kind of thought that batteries had comprehensively won in this market, tbh. I still can't quite get used to the electric buses. A 20 tonne double-decker bus should sound like it might explode at any moment; it is unnatural for them to move around more or less silently.

In Tompkins County we were early adopters of the electric bus, at least for the American market. We bought them from a startup which had trouble with the structural aspects and eventually they fell apart https://www.ithaca.com/news/ithaca/tcat-pulls-all-electric-b... Established bus manufacturers make good electric buses now but we don't have the money to buy replacements.

Five months before the company filed for bankruptcy, Proterra's CEO was appointed to the President’s Export Council (PEC), "the principal national advisory committee on international trade."

Re: Why do transit agencies keep falling for the hydrogen bus myth?

#100

Post by abdullahkhalids »

bluGill wrote: post #66
abdullahkhalids wrote: post #47

Earlier quoted context omitted.

Many bus routes have a 5-10ish min break at some point (usually the main station) in the route. If you can utilize those ten minutes to do a top-up, you can go a lot further on the same sized battery.

No bus route should be more than 15 minutes between full and empty. That is you start at some station, go 15 minutes, then turn around and go back. There are many systems that attempt to do more, but there is no point: people have places to be: on the bus is not on that list. That 15 minutes means an average of 7 minutes, now they walk to some other express bus that gets them nonstop (at faster speeds) to someplace,…

There are two critical aspects to the bus routing problem. One is that no matter how well you design your system, there is always variance in the arrival times of a bus at any given stop. If you expect people to switch buses, then you need to account for this variance, and this means adding buffers. Nothing makes people stop using buses faster than missing your connection because your bus was late.

The other aspect is the what city topology you are dealing with. In square grid cities, you can probably put a tram on every road, and with one switch over, get to where ever you need to get to.

But many organically grown cities end up using the hub-and-spoke model, where there are main stations where many different buses meet. People switch over to the next connection (and you need a buffer here). Critically, you need all the buses to meet at roughly the same clock time, say every 30 min. Now, one thing you realize immediately is that not all routes are equal. One route might be only 25 min, Either you make it longer and waste fuel, and time for everyone sitting on the bus, or you wait an extra 5 min at the main station.

Bus scheduling is very difficult problem in real cities with weird topologies and real traffic issues. Buffers are a necessary part of any reasonable solution.

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