> the weight of batteries is a problem for larger vehicles that need long range, like a bus, truck, or plane. For those hydrogen might be better.
China is already leading the world in electric busses. They work great. Busses are such good vehicles for batteries, that for some routes it may even make sense to run them with super-capacitors, with chargers embedded in the road at stops.
Trucks are always going to be a problem. This is probably the area where H2 might have the best shot. The big problem, however, is that they are a relatively small portion of vehicles. If they're the only ones running H2, it's probably not going to work.
Airplanes, for the most part, aren't going to be electric (although I've heard rumblings of short-range commuter electric aircraft being planned). I doubt they'll be hydrogen powered either. While they aren't as encumbered by the rocket equation as... rockets, they do feel pressure from additional weight. Additionally, the added volume of H2 compared to something like avgas (on a MJ normalized basis) would negatively affect the aerodynamic efficiency of airplanes. Probably going to stay with petroleum for the foreseeable future.
> Busses are such good vehicles for batteries, that for some routes it may even make sense to run them with super-capacitors, with chargers embedded in the road at stops.
I would think busses are a very poor fit for batteries: their economics favours driving around for as long as possible (switching drivers in shifts). Any time spent charging is a waste.
This is less favourable than a consumer car, which sits around unused for most of the time (hence easily charged) and usually only makes a few short trips a day (e.g. commute).
I can understand the desire for supercapacitors on busses, since they are much quicker to charge than batteries. Putting chargers in the stops is a way to mitigate the low energy density of supercapacitors: they only need to last as far as the next charging point.
I think supercapacitors + fast charging stops makes busses very suited for electricity; but I don't think they're best suited for batteries (the fact that there are battery-powered busses shows that there's enough wiggle-room in the economics that they can work despite this unsuitability).
For aircraft, fuel characteristics relative to airframe and payload also matters.
Liquid hydrocarbons store readily in wing tanks at temperatures from (roughly) -50C to 50C. Pasengers and cargo can be allocated to fuselage, arranged in a contiguous space for the length of the craft.
Pressurised hydrogen favours cylyndrical or spherical tanks, located near the fore-aft midpoint of the craft, effectively segmenting the (pressurised) fuselage in two; before-pressure-vessel and aft pressure-vessel . Cryogenic hydrogen would require Dewer vessels and venting with considerations for mitigating hydrogen explosion risk -- present over a wide range of concentrations.
And in both cases, metal embrittlement and molecular leakage occur.
Adding a few carbon chains mitigates all these factors.
>If they're the only ones running H2, it's probably not going to work.
Aren't they practically the only ones running diesel currently? Maybe Trains + other diesel vehicles is a surprisingly large percentage, but... I'd be surprised.
A small percentage of vehicles by sheer number perhaps, but not by miles travelled. An average truck is working 50 hr weeks, plus commute time for the driver etc. As opposed to your average car which runs twice a day for 30 mins.
Still a small percentage. While the average car is 30 minutes twice a day, the small percentage of cars that are not average are still more than the trucks. People on vacation can drive all day. The average car is used for a dentist appoint in the middle of the day once in a while - this all adds up to a lot of cars on the road.
> China is already leading the world in electric busses. They work great. Busses are such good vehicles for batteries, that for some routes it may even make sense to run them with super-capacitors, with chargers embedded in the road at stops.
Alberquerque had to return electric buses because they didn't perform up to the range requirements.
Electric bus range goes down the moment you introduce any sort of elevation, which is why Shenzhen, a relatively flat city, has them, and Hong Kong, an extremely hilly and mountainous city, considered the pilot a failure.
Shenzhen has quite severe elevation differences (which is why a lot of it is unbuilt, even though land values are extremely high) but the bus network was planned to run mostly on the flat bits. HK, being heavily built up already, does not have the luxury of being able to do such planning.
China is already leading the world in electric busses. They work great. Busses are such good vehicles for batteries, that for some routes it may even make sense to run them with super-capacitors, with chargers embedded in the road at stops.
Trucks are always going to be a problem. This is probably the area where H2 might have the best shot. The big problem, however, is that they are a relatively small portion of vehicles. If they're the only ones running H2, it's probably not going to work.
Airplanes, for the most part, aren't going to be electric (although I've heard rumblings of short-range commuter electric aircraft being planned). I doubt they'll be hydrogen powered either. While they aren't as encumbered by the rocket equation as... rockets, they do feel pressure from additional weight. Additionally, the added volume of H2 compared to something like avgas (on a MJ normalized basis) would negatively affect the aerodynamic efficiency of airplanes. Probably going to stay with petroleum for the foreseeable future.