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Hydrogen vs. Battery Buses: A European Transit Reality Check

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Re: Hydrogen vs. Battery Buses: A European Transit Reality Check

#141

Post by ViewTrick1002 »

bluGill wrote: post #117
adgjlsfhk1 wrote: post #37

Earlier quoted context omitted.

Lots of busses are split shift. i.e. they drive from ~6:30am to ~9:30am and ~4pm to 7pm. This means that a significant portion of your bus fleet will be able to charge during the middle of the day when energy demand is relatively low and there's a ton of solar power. As an aside, we have so far really dropped the ball on level 1 electric vehicle chargers at offices. As solar power and EV numbers increase, it's pretty…

Split shift is a stupid idea that needs to die. It only works for people who always work '9 to 5'. Work a different shift and you drive. Need to go shopping - just drive. Have a day off - drive to whatever you do. Going to church one sundap - drive. Have a kid who might get sick at school - you better drive everyday.

In cities with working public transport it aligns the schedules to accommodate the ridership. Which sucks a bit in the late evening when headways might become a bit long.

The absolutely largest peak is in the morning and then a smaller one in the afternoon.

So you might have a baseline like every 10 or 15 mins and then in rush hour it is every 3 or 5 mins.

Re: Hydrogen vs. Battery Buses: A European Transit Reality Check

#142

Post by philjohn »

fluidcruft wrote: post #134
philjohn wrote: post #122

Earlier quoted context omitted.

https://www.sciencedirect.com/topics/engineering/fuel-cell-e... I believe all Hydrogen vehicles are using proton exchange membranes still, which have roughly 40-50% efficiency. And that's before you take into account that even the most cutting edge hydrogen refining processes are around 70% efficient. So 1kWh of energy input (electricity) will net you 3X the motive power when used directly in a BEV than first being c…

BEVs aren't 100% efficient though so it's closer to 2x rather than 3x.

I’ve also gone for the max efficiency figures for the Hydrogen car.

And that’s before we get to the fuel costs - £90 to go 400 miles in a Mirai, versus £5.50 to go 300 in an EV6.

Re: Hydrogen vs. Battery Buses: A European Transit Reality Check

#144

Post by Filligree »

petertodd wrote: post #139
praseodym wrote: post #111

Earlier quoted context omitted.

> Yes, you can refill quicker Unless the hydrogen fueling nozzle freezes to the car, which is apparently quite common in high humidity weather and/or when multiple cars are fueled consecutively. See e.g. https://www.sciencedirect.com/science/article/pii/S036031992...

That's just a minor problem, not a fatal flaw. Obviously you can fix that with a small heater for negligible energy cost.

Now you have a heater in immediate proximity to hydrogen gas.

It’s not impossible, but I think you’re underestimating the complexity of doing that safely.

Re: Hydrogen vs. Battery Buses: A European Transit Reality Check

#145

Post by preisschild »

bluGill wrote: post #118
jillesvangurp wrote: post #67

Earlier quoted context omitted.

Batteries are cheap. Installing lots of copper lines for trolley buses isn't. That's why trolley buses are pretty rare. Old idea, didn't really take that well. There are a handful of cities that have them. And they've had them for decades. Most of those cities now also have battery electrical buses to service all the areas where the cables don't go. Expanding the network of cables doesn't seem to have a very high pri…

Trolly wires generally work out cheaper than batteries if you are running frequent service. Batteries work out better anyway though because they allow you to go around obsticals (roadwork, cars illegally parked in the land...)

> Batteries work out better anyway though because they allow you to go around obsticals (roadwork, cars illegally parked in the land...)

The pantographs of trolleybuses are often pretty long, so they can switch to the other lane to avoid obstacles.

Re: Hydrogen vs. Battery Buses: A European Transit Reality Check

#146

Post by rad_gruchalski »

Filligree wrote: post #144
petertodd wrote: post #139

Earlier quoted context omitted.

That's just a minor problem, not a fatal flaw. Obviously you can fix that with a small heater for negligible energy cost.

Now you have a heater in immediate proximity to hydrogen gas. It’s not impossible, but I think you’re underestimating the complexity of doing that safely.

Hydrogen ignition temperature is 535°C.

Re: Hydrogen vs. Battery Buses: A European Transit Reality Check

#147

Post by crote »

nautilius wrote: post #113
philjohn wrote: post #92

Earlier quoted context omitted.

Yes - but Hydrogen vehicles have not proven to match or even beat EV's in a lot of key metrics that matter. The biggest one is efficiency. 40% efficient is one figure I saw, versus 80% for EV's. Yes, you can refill quicker, but time to "refuel" EV's is dropping precipitously as well, and it's just all around safer than tanking around highly combustible liquid gas.

Efficiency is the standard red herring of the battery crowd - if efficiency was the prime motivation, we would all be driving bicycles and SUV or sportscars would not exist. What are your other metrics? It’s an electric drivetrain with all advantages, but with the range of a gasoline car. Refueling cNG or LNG is standard in Europe, LH2 works just fine. Google “burning Tesla” for that ridiculous take on why batteries…

Range is almost entirely irrelevant.

The average commute distance is 16 miles, and commutes over 50 miles are quite rare. This means a car with a range of 100 miles would cover the vast majority of use cases. Add some buffer for emergencies and cold weather, and even the 150-mile-range Nissan Leaf is more than enough.

You could also look at once-a-year road trips, of course: a range of 250 to 300 miles is becoming quite common for mid-level SUVs. With current technologies that means a charging session of 30 minutes or so every 3.5 to 4 hours - and it's only getting better. For context, the EU-based commercial truckers have a 45-minute break every 4.5 hours, because non-stop driving for even longer than that poses a safety risk.

BEVs aren't stuck in the 1990s anymore. Their range has significantly improved over the 60-mile range of the GM EV1. If 2025 BEV range is an issue for you, you are the outlier.

Re: Hydrogen vs. Battery Buses: A European Transit Reality Check

#148

Post by crote »

01HNNWZ0MV43FF wrote: post #40
rsynnott wrote: post #4

I think battery buses have comprehensively won this one, to be honest. The biggest hydrogen bus fleet seems to be 35 vehicles; there are many BEV bus fleets in the hundreds and some in the thousands. As a certified old person, I'm having trouble getting used to them. It is unnatural for a double-decker bus to pull up near-silently, and then move off smoothly when you get on. They are _supposed_ to vibrate violently a…

I'm surprised hybrids are so under-represented in this considerations. Maybe I'm missing something but I would think at the scale of a bus, a hybrid is even more appealing than at the scale of a sedan. Even locomotives and one or two earthmoving off-highway trucks have electric transmissions, making them series hybrids (With very small batteries not used for traction)

Hybrids are attractive when a short battery range is enough for daily use but you still do semi-frequent long-range driving. Rather than hauling around a heavy and expensive XL battery pack on your daily commute you haul around a tiny combustion engine. It's a great solution for people with range anxiety.

Buses have a completely different use case. They drive a well-known distance, and every day is practically identical. It is fairly easy to scale its battery pack to closely match the actual range needed. Running a true long-distance route like a Greyhound or Flixbus, which physically can't be battery-based yet? Just stick to diesel for now.

Re: Hydrogen vs. Battery Buses: A European Transit Reality Check

#149

Post by crote »

martinald wrote: post #7
m4rtink wrote: post #2

I'm not really sure there is any place for a discussion - you would need a whole new infrastructure for hydrogen powered buses, while keeping a lot of the downsides of fossil fueled air breathing vehicles (eq. air filters filters regardless of if you burn the hydrogen or use it in fuel cells). With battery buses - you might need to slightly beef up the local transformer and installs some new wires and that's it. Or e…

While I agree with you; just to be clear it's not "slightly" beef up the local transformer. If you imagine a medium sized depot with 50 buses stabled at any one time, and 300kW chargers (I believe you could go higher), that's 15MW peak which is not trivial to add in many cities overnight. You really need some sort of HV connection for that kind of load, the existing local LV distribution grid isn't going to handle it…

You wouldn't need 300kW chargers, though!

Battery buses have a battery capacity of around 400kWh. Assuming they are stabled for 6 hours overnight, that's only a charging power of 66kW. Suddenly your depot needs a connection with a peak capacity of 3.3MW instead of the proposed 15MW.

This can get significantly better in practice. There's a peak transit demand during commute hours, but that means there are quite a few unused buses in the middle of the day. Those can charge at the depot to take advantage of cheap daytime solar. A lot of bus routes are timed, with a waiting time of 5 to 10 minutes at the turnaround point. Place an overhead charger here, and the charging demand can be distributed across the day. As a bonus, this also reduced the battery capacity needed - and the associated lower weight reduces total energy demand as well.

Sure, bus depots are going to need beefy connections, but that's hardly an insurmountable obstacle. The ongoing rapid rollout shows that it simply isn't a such a big issue in practice.

Re: Hydrogen vs. Battery Buses: A European Transit Reality Check

#150

Post by crote »

credit_guy wrote: post #125

Hydrogen is difficult to store. But it enjoys the square-cube law. If you increase the size of a tank by a factor of 2 in all 3 dimensions, the capacity increases by a factor of 8, but the cost only by a factor of 4. Hydrogen has some huge advantages over other green options. But, also some huge disadvantages. If you want to diminish the disadvantages, you need to exploit the square-cube law, and that means you need…

> It could work very well for trains.

Only if you completely ignore overhead wires. Electrifying main rail corridors is a no-brainer, and batteries are more than sufficient for short last-mile spurs.

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