Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Hydrogen vs. Battery Buses: A European Transit Reality Check

cleantechnica.com

Post reply on HN
Print view View original

41–50 of 193 posts

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

#41

Post by vardump »

Kirby64 wrote: post #34
vardump wrote: post #33

Earlier quoted context omitted.

Don't fuel cells require air without any contaminants, thus air filters? So you still need filters, this not for the exhaust, but for the intake.

Is that a real problem here? Air filters on ICE cars are easy and not that frequent. You need cabin air filters regardless for passengers, so changing those at the same time isn’t that much different. Filters are cheap unless fuel cell ones are super expensive for some reason.

The air purity requirements for fuel cells are rather demanding. Impurities will destroy them.

ICE air filter would destroy them in no time.

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

#42

Post by londons_explore »

VectorLock wrote: post #29
londons_explore wrote: post #18

Busses currently have big engines and fuel tanks (or motors and batteries). That intuitively makes sense - obviously a big vehicle needs more energy than a small one like a car. However, typical city bus routes spend most of their time under 30 mph, cutting aerodynamic drag by a whopping 90% compared to 70 mph highway cruising that a car does. With more work on rolling resistance (buying super-good bearings and fancy…

I'm not sure how important double glazing is when you're opening the inner air volume to ambient air every few minutes, but maybe?

It's possible something could be done about that with air curtains, PVC strip curtains, etc.

Climate control energy varies widely depending on geography - and appropriate door energy saving approaches will probably depend on where the bus operates, and possibly even the season (ie. winter doors swapped for summer doors), or extra batteries added in summer/winter to account for the extra energy use.

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

#43

Post by Kirby64 »

vardump wrote: post #41
Kirby64 wrote: post #34

Earlier quoted context omitted.

Is that a real problem here? Air filters on ICE cars are easy and not that frequent. You need cabin air filters regardless for passengers, so changing those at the same time isn’t that much different. Filters are cheap unless fuel cell ones are super expensive for some reason.

The air purity requirements for fuel cells are rather demanding. Impurities will destroy them. ICE air filter would destroy them in no time.

Hm, I looked up how much a Toyota mirai filter is and they’re quite expensive. $270 it looks like from a 3rd party? It’s every 36k miles though. Not every year/12k like a normal air filters.

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

#44

Post by vegavis »

Yeah this only reveals a snapshot of the current situation. The truth is that lithium ion has a few more decades of serious R&D and successfully mass produced commercial products on the market. Hydrogen fuel cells arent as fortunate; they still have a high production cost due to low volume, the supply chain has had a fraction of the investment of ICE and EV, and the regulatory environment is even less clear than EV around the world.

But the reality is our society is well on its way to fracturing the fossil fuel dominated infrastructure supporting us, and it wont just be electric to take a piece of the pie. Buses and other large vehicles like mining vehicles, semis, and many Class A vehicles will transition from their diesel engines to instead fuel cell, and not batteries. Battery technology is far too heavy to support vehicle and payload combinations at this level, and these applications prefer the high power density of fuel cells over the accessibility and storage capability of an EV only architecture. Hydrogen is a quicker refuel, and one can imagine a future where industrial sites and logistics warehouses that already have forklifts running on H2 will see the rest of their large work/fleet vehicles transition over to hydrogen as well.

Unfortunately, this premonition is probably at risk of being a few years off thanks to the current government situation.

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

#45

Post by vegavis »

Kirby64 wrote: post #9
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…

> 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). Unless you burn the hydrogen, you aren't producing any emissions... unless you count water as an emission. Fuel cells don't produce any emissions. Burning hydrogen though, does prod…

Fuel Cells have a lot in common to ICE. They require a significant balance of plant that helps provide air to the fuel cell, coolant for many of the components, electronics controller and significant electrical harnessing, bracketry for support, filters, coolant pump, air source, radiator... etc.

in one way it is a downside since its more parts and complication than maybe a pure EV architecture, but the similarities to ICE arch means that its an attractive option to transition to for both the OEMs and a tiered supply base used to working on ICE vehicles. If you can get economies of scale going and bring cost down for fuel cell its a great replacement for many (not all) ICE archs.

They are preferred solutions for larger vehicles because of the weight of lithium ion batteries. also because theyre optimized for power density while electric architectures excel with energy capacity/storage. But if you can implement infrastructure at the locations where these larger Class A vehicles are (or busses), then you dont care about capacity for the known universe's lightest (resting mass) fuel as much since H2 refuel times are fast.

You are correct about boats though, it is also a good solution set there. Planes will only work if we can achieve air cooled hydrogen fuel cells and eliminate the expensive and heavy balance of plant (Hysata).

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

#46

Post by 7e »

vardump wrote: post #33
Kirby64 wrote: post #9

Earlier quoted context omitted.

> 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). Unless you burn the hydrogen, you aren't producing any emissions... unless you count water as an emission. Fuel cells don't produce any emissions. Burning hydrogen though, does prod…

Don't fuel cells require air without any contaminants, thus air filters? So you still need filters, this not for the exhaust, but for the intake.

Yes, hydrogen cars clean the air as your drive them.

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

#47

Post by 7e »

londons_explore wrote: post #30
maxerickson wrote: post #25

Earlier quoted context omitted.

The low speed means they are using the power to accelerate against inertia, not to maintain speed against air resistance.

0.7 m/s^2 is a typical acceleration for a city bus - most people won't fall over whilst standing at that acceleration. A city bus perhaps holds 50 70kg passengers = 3.5 tons of cargo, and a lightweight bus design is perhaps 6.5 tons (typical bus=10 tons). Total = 10 tons. Peak Power required to accelerate 0.7 m/s^2 up to 30 mph = 93 kilowatts. Which is car territory. The cheapest tesla model 3 has a 208 kilowatt moto…

The bus is constantly starting and stopping. Regen doesn't recapture it all. Power isn't the issue, energy is.

Also, current hybrid busses with not-so-heavy batteries weigh about 15 tons without cargo. You are way off.

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

#48

Post by 7e »

VectorLock wrote: post #28
maxerickson wrote: post #25

Earlier quoted context omitted.

The low speed means they are using the power to accelerate against inertia, not to maintain speed against air resistance.

Inertia that can then be recovered, which you can't with air resistance.

There is plenty of air resistance in a low speed bus, which is shaped like a brick and has huge frontal area. That is still a lot of air to push.

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

#49

Post by m463 »

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)

I wonder if diesel electric locomotives are efficient at all.

I think the electric is for infinite torque to get lots and lots of cars moving. But to slow down, "electric" brakes are to bleed off power into resistor banks, not re-capture the electricity.

Meanwhile an electric bus actually has to be efficient, which means batteries and regenerative braking.

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

#50

Post by deepsun »

api wrote: post #13
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…

Where I live in the US my kids still take “cheese buses” to school that haven’t changed a bit. They’re diesel and you can hear them blocks away. When they pull up with their air brakes going off and their diesel shifting to idle it sounds like one of those spice miner things from Dune going to work. If they ever go electric I’m not sure how we’ll know it’s time to take the kids out. Won’t be able to hear them coming.

You'll see the bus on your phone / home hub. Like ridezoom company does, you see whenever your kid checked in/out of the bus, and the bus itself on a map.
Post reply on HN