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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?

#131

Post by jrussino »

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.

> A 20 tonne double-decker bus should sound like it might explode at any moment

I hope you're using "should" as in "that's what I'm accustomed to" rather than "that's how it ought to be"... right? :-D

Personally I feel like quieting buses would be a huge step toward making day-to-day city life more pleasant.

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

#132

Post by MostlyStable »

AnthonyMouse wrote: post #96
jshier wrote: post #32

Earlier quoted context omitted.

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…

Wouldn't an additional advantage of series hybrids be that the engine can be tuned to operate solely in it's most efficient RPM band, since it just charging the battery and doesn't need to deal with changing speeds? This can (according to some very cursory googling), result in efficiency gains of 20-30% relative to the least efficient RPMs. This should at least partially offset some of the size and weight considerations, since you don't need to size the engine for it's energy output in less efficient speeds. This seems like it would be most important in stop-and-go conditions where the engine is spending considerable time at less efficient speeds, such as in a bus.

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

#133

Post by why_at »

manchego wrote: post #107

I'm just waiting for flywheel powered buses to make a return: https://en.m.wikipedia.org/wiki/Gyrobus

Wow I had no idea this existed

>Disadvantages

>Weight: a bus which can carry 20 persons and has a range of 2 km (1.2 mi) requires a flywheel weighing about 3 tons.

>The flywheel, which turns at 3000 revolutions per minute, requires special attachment and security—because the external speed of the disk is 900 km/h (560 mph).

It's truly a mystery why they never caught on

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

#134

Post by em500 »

vardump wrote: post #50
xnx wrote: post #35

Earlier quoted context omitted.

Some hybrid drivetrains have fewer moving parts than a traditional ICE and are more reliable.

Sounds counterintuitive. Any references?

At least for Toyota hybrids, the intuition is that the traditional ICE transmission system is replaced by what Toyota calls a "power split device" which continuously feeds and balances the electric and combustion power sources. This power split device uses a simpler gearing system (enabled by the high torque electric motors) and appears to be mechanically simpler and more reliable than traditional transmission systems (which probably wear out quicker than the engine in most ICEs).

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

#135

Post by golemiprague »

AnthonyMouse wrote: post #96
jshier wrote: post #32

Earlier quoted context omitted.

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…

[dead]

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

#136

Post by pjscott »

neves wrote: post #125

Why? Because Oil Companies are lobbying for inefficient hydrogen to delay a green revolution: https://adamtooze.substack.com/p/carbon-notes-5-green-hydrog... > The members of the hydrogen coalition are all obviously incumbent fossil fuel and petrochemical interests looking for a bridge to the new era. If realized, their ambitious hydrogen projects may overload the available supply of green power, for little real bene…

Do you have actual knowledge of their motives? Or is this speculation, confidently stated as fact?

Another possible motive, mentioned in the the paragraph you quote, is that the oil companies see an energy transition coming and are trying to get aboard the hydrogen train to diversify their future revenue sources. And that sounds like a reasonable motive; the sort of thing that people who don't see themselves as evil villains – i.e. the supermajority of people – could embrace.

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

#137

Post by NikkiA »

Ericson2314 wrote: post #122
manchego wrote: post #107

I'm just waiting for flywheel powered buses to make a return: https://en.m.wikipedia.org/wiki/Gyrobus

Cool :) but reminds me that all energy storage is scary and an accident waiting to happen. Flows > stocks, overhead wire for the win!

I personally think Battery buses with SAE J3105 'docking' points at key stops (basically, the stops that are used to loiter to set timing, rather than leaving as soon as possible) is a better solution than the cost of stringing OHL through every major road in a city.

https://en.m.wikipedia.org/wiki/Battery_electric_bus#Chargin...

https://en.m.wikipedia.org/wiki/SAE_J3105

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

#138

Post by adamanonymous »

why_at wrote: post #133
manchego wrote: post #107

I'm just waiting for flywheel powered buses to make a return: https://en.m.wikipedia.org/wiki/Gyrobus

Wow I had no idea this existed >Disadvantages >Weight: a bus which can carry 20 persons and has a range of 2 km (1.2 mi) requires a flywheel weighing about 3 tons. >The flywheel, which turns at 3000 revolutions per minute, requires special attachment and security—because the external speed of the disk is 900 km/h (560 mph). It's truly a mystery why they never caught on

You missed the last and most funny one

>Driving a gyrobus has the added complexity that the flywheel acts as a gyroscope that will resist changes in orientation, for example when a bus tilts while making a turn, assuming that the flywheel has a horizontal rotation axis.

So you have a giant blender than can travel one mile in a straight line before needing to be recharged

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

#139

Post by mike-the-mikado »

adrian_b wrote: post #110
AnthonyMouse wrote: post #82

Earlier quoted context omitted.

That's efficiency, not range. Suppose hilly terrain reduces range by a third for electric vehicles and half for diesel. The diesel bus just fills up twice as often. The electric bus needs a 50% bigger battery in order to finish the same route without stopping to charge, and then it becomes 70% because it has to lug the bigger battery up the hills. You can just... do that, but that doesn't mean it's not a thing you ha…

It is impossible for a hilly terrain to reduce the range by a third for well-designed electric buses. The efficiency of regenerative braking increases with the power of the vehicle. The electric efficiency should be well over 90%, perhaps even 95%. The mechanical losses will lower the total efficiency to much smaller values, but even so, the total efficiency should be over 80%. A bus with an ICE will consume 5 times…

If the passengers all ride up hill and walk down hill?

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

#140

Post by analog31 »

yummypaint wrote: post #126
calibas wrote: post #109

Back in 2003, President George W. Bush announced the Hydrogen Fuel Initiative. At the time, people criticized the effort as an attempt by the oil industry to shift attention away from electric cars. The oil industry knew that hydrogen power wasn't going to be viable anytime soon, while electric cars were already a direct threat to their profits, so they pushed the US government towards hydrogen power. Not to disparag…

It absolutely was. In the event that breakthroughs happened and it became viable faster than expected, the backup plan was to get the hydrogen from fossil fuels to make sure the industry would still get its cut.

Isn't that the only plan right now? Is commercially viable hydrogen being made from any process other than the shift reaction?
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