Why do transit agencies keep falling for the hydrogen bus myth? • Hacker News Board

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

#311

Post by jimnotgym » Sat, Mar 15, 2025, 9:44 AM UTC

VBprogrammer wrote: post #302

jimnotgym wrote: post #296

Earlier quoted context omitted.

Very interesting, but it is a niche specific case that doesn't answer the question at all. Imagine a tractor in a field. What is the solution for that?

I don't think a tractor is necessary a bad use case for batteries. They just need battery packs which can do the equivalent of a days work. Electric motors are almost better suited to the use case due to the torque. I'm sure some of the US mega farms have tractors which run all night (and the emissions of those are the least of their environmental issues) but this isn't common elsewhere.

I believe the problem is that a tractor runs for much of the workday at a very high load. Pulling a plough is constant hard work, not like a car that is only using a lot of power while accellerating hard. If you had your foot to the floor in a Tesla constantly you would run your battery flat in a lot less than 8 hours. I have read that the batteries for this application would therefore be infeasibly large.

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

#312

Post by MayeulC » Sat, Mar 15, 2025, 9:47 AM UTC

jasonkester wrote: post #284

iamthemonster wrote: post #231

Earlier quoted context omitted.

I work for an oil and gas company. It has been specifically stated by my company that they are seeking support for hydrogen as a fuel because it adds value to their gas reserves - natural gas is roughly 75% hydrogen on a molar basis. The idea is to stimulate demand for "green-ish" hydrogen (that is by grid-connected electrolysis); once demand for the hydrogen is there, it can be supplied by blue hydrogen. The O&G com…

Can you define your hydrogen colors for us? It sounds like you have something interesting to say, but I can’t parse what it is out of your company’s jargon.

These are common terms. A random link: https://www.weforum.org/stories/2021/07/clean-energy-green-h...

* Green: produced from surplus renewable capacity (electrolysis)

* Black, brown, grey: convert various fossil fuels to hydrogen via steam reforming. Basically strip carbon from hydrocarbons, emitting a lot of CO2.

* Blue: same as black/brown/Greg but with carbon capture.

There are other (less common) shades as well.

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

#313

Post by jimnotgym » Sat, Mar 15, 2025, 9:50 AM UTC

defrost wrote: post #298

jimnotgym wrote: post #296

Earlier quoted context omitted.

Very interesting, but it is a niche specific case that doesn't answer the question at all. Imagine a tractor in a field. What is the solution for that?

A billion tonnes per annum is niche ? What's the tonnage the tractor moves per annum?

Yes your example is extremely niche. It only works where you are going to work on one specific application for many years in the same place. It doesn't generalise to building a house, a supermarket or a road. It doesn't generalise to ploughing the Mid-West.

Even in your example it only works if you are taking all of the material to one destination, like an ore refinery. If it was road stone, the rock would get loaded onto a diesel truck for the final part of the journey. So again, the tractor, the excavator on a job site, the lorry, will all stay on diesel or hydrogen ICE

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

#314

Post by baq » Sat, Mar 15, 2025, 9:50 AM UTC

m463 wrote: post #193

mixermachine wrote: post #151

Earlier quoted context omitted.

One can extract hydrogen from fossil fuels. So if a hydrogen break through is coming, they already have a cheap source for the material. Not really green though...

not really cheap either. I remember natural gas vehicles (busses and cars, like the honda civic). You could actually fill up at home if you had natural gas, but the electricity just to compress the natural gas for the car cost as much or more than the compressed fuel in the car. For hydrogen, it is even harder. take a look at cars running compressed hydrogen. I remember $17 for the equivalent of a gallon of gasoline.…

Dollars are fake, or more accurately, a social construct, remember that. You can always tax the cheaper fuel and subsidize the more expensive one.

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

#315

Post by D_Alex » Sat, Mar 15, 2025, 9:52 AM UTC

ajb wrote: post #304

D_Alex wrote: post #293

Earlier quoted context omitted.

"Blue hydrogen" is commonly used for hydrogen produced from natural gas. If it is produced by steam reforming (most common), then the associated CO2 emissions are worse than if you just burn the natural gas directly. "Green hydrogen" is usually hydrogen produced from water by electrolysis, using electricity from non-CO2 source, e.g. wind or electricity.

Blue hydrogen is supposed to capture the carbon. If its just emitted, then it's grey hydrogen: https://www.nationalgrid.com/stories/energy-explained/hydrog...

You are entirely correct.

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

#316

Post by baq » Sat, Mar 15, 2025, 9:52 AM UTC

marshray wrote: post #281

somat wrote: post #254

Earlier quoted context omitted.

It flows, you use fluid equations to describe it's state. I will grant that it flows in a different medium than molecular fluids. but that does not prevent it from being a fluid. As for what is flowing, my understanding is that it is electrons in an em field. which if you think about it is almost the same thing that is flowing in a molecular fluid, only that has drag a bunch of protons around at the same time limitin…

What is "static electricity" then?

Potential difference without flow. A discharge is a dam breaking.

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

#317

Post by jillesvangurp » Sat, Mar 15, 2025, 9:53 AM UTC

boplicity wrote: post #176

jillesvangurp wrote: post #67

That goes for anything hydrogen and wheels pretty much. It's actually pretty simple to figure out. Making hydrogen takes energy. You lose some of the energy making the hydrogen. This is not a fixable problem. At least not unless you break the laws of thermodynamics. When you have created hydrogen, you lose more energy compressing the energy. Then you have to transport it to wherever it's going to be pumped into the v…

The argument for hydrogen has to do with energy density. There are certain use cases where batteries are just too heavy, but hydrogen, with its higher energy density, is not. Maybe that will change in the future, but as it stands now, energy density is a significant barrier to adoption of battery/electric in certain areas. The cost of energy doesn't matter if it can't be used due to batteries being too heavy. It's po…

The fallacy with that argument is that hydrogen's volumetric energy density is very low.

In liquid form, methane has about 2.7x more energy by volume than hydrogen. Diesel has 4.2x more energy. Keeping and transporting hydrogen in liquid form takes a lot of energy and requires constantly boiling it off to keep it liquid. In practice, most hydrogen is transported in compressed gas form (700 bars). In that form, you need about 11 hydrogen truckloads to a single diesel truckload.

So, it takes up a lot of space. This makes it very impractical for transport use cases. Unless you convert it to something that maybe contains hydrogen but also other atoms. Like carbon (carbohydrates) or nitrogen (e.g. ammonia). Converting it to those forms takes more energy. And those multiply. And doing the chemical conversion back to energy in a combustion engine has the same problem as all combustion engines: it loses most of the energy as heat. Fuel cells might improve on that; but they'd still be losing energy.

This is why battery electric trucks easily match the ranges of most hydrogen trucks on the road. There are currently no production hydrogen trucks or buses that offer a longer range than their battery-electric equivalents. You'd need significantly larger tanks and adding the same volume in battery would match the range easily. Even with current production batteries (160-200 wh/kg), which are about a third of the energy density of already announced new state of the art batteries (500wh/kg). Batteries are on a path of steady volumetric an mass density improvements. Hydrogen will never get better than it already is.

It's also why hydrogen planes are no longer being considered a viable plan by the likes of Airbus; most of the plane would have to be reserved for hydrogen containment.

For ships, using hydrogen as a fuel is not a serious option either. Simply too much volume. Transporting hydrogen by ship in liquid form loses 1-2% of the load per day to boil off. This is the only way to keep it liquid; boiling it off cools the liquid. The longer the journey, the more hydrogen is lost to unavoidable boil-off, making long-distance transport highly inefficient.

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

#318

Post by jimnotgym » Sat, Mar 15, 2025, 9:58 AM UTC

D_Alex wrote: post #305

jimnotgym wrote: post #292

How much power does it take to charge a bus in a reasonable amount of time? I heard 100kw. If I have 100 buses charging overnight at 100kw I guess I need 10Mw grid connection? Is that an easy thing to get to a city bus depot in the US. In the UK I believe that would require moving to a location with a HV line and building a sub-station.

No, that is not right. The correct answer is "it depends", but let's run some indicative numbers on data for Boston: On average and excluding the minority of routes with dedicated lanes (which may be best run on diesel), the Boston metro buses are in use for 6.6 hours per day, covering on average 53 miles. A full size electric bus uses electricity at a rate of approx 2 kWhr/mile. So, on average the bus would have aro…

Not difficult...

But in the UK you would need HV powerlines overhead and 5 years of planning to get a 1MW connection

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

#319

Post by ajb » Sat, Mar 15, 2025, 10:06 AM UTC

alvah wrote: post #252

semi-extrinsic wrote: post #235

Earlier quoted context omitted.

Oil pipelines, no. Gas pipelines, yes. The effort to requalify existing gas pipelines for hydrogen use is well underway in Europe. There might be a need to run at lower pressure, depending on the type of steel, but leaks are not an issue.

Hydrogen embrittlement is a massive issue, I’d be interested to hear how this can be engineered around. My understanding is it requires more exotic materials than those used in any existing NG or oil pipelines. Everything I’ve seen claiming it’s viable to use existing infrastructure seems reasonable at first glance, but invariably contains a massive hand-wave or 2.

The existing infrastructure was originally built for town gas which is ~50% hydrogen, and run successfully for many decades as such. So this is mainly about checking out the more recently designed parts. My understanding is embrittlement is mainly a problem for storage tanks, which need to use high strength materials due to the enormous pressure -and ironically those materials are more susceptable.

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

#320

Post by Smithalicious » Sat, Mar 15, 2025, 10:11 AM UTC

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…

It seems to me like green fundamentalist see nothing but enemies and subterfuge everywhere. Hydrogen, biofuel, nuclear, switching from oil to natural gas where possible, the list goes on.

I don't have enough of an opinion to comment on anyone of them individually, but I notice a really striking pattern where every time the idea of alternative energy sources are brought up that are not wind or solar, whoever brings it up is accused of sabotaging the energy transition in some way or another.