[wolfekeeper]

Have you considered the weight and cost of the container?

Every liquid-fuelled rocket designer has.

Actually, the low density of liquid hydrogen fuel is a huge problem even for rocketry. It's only practical if it's used with dense liquid oxygen which raises the average propellant density. But some designs such as beamed power rockets would ideally use only hydrogen fuel (due to its low molecular mass, which gives a high exhaust velocity). But in practice that works badly because the tankage is so heavy relative to the contents.

In a car, the tankage weight is not such an issue, because the rest of the car is so heavy, but it's completely impractical; everything would have to be thermos flasked. Also production of liquid hydrogen is incredibly energy intensive far more so than simply electrolysis of hydrogen. The heat capacity of hydrogen is MASSIVE (multiple times that of H20 which is huge to start with), so the liquefaction gets ridiculous, and there's other complications relating to spin isomers as well.

In rocketry the downsides of liquid hydrogen make it a slight loss during take off compared to hydrocarbon fuels, but the higher exhaust velocity and lower overall stage weight pays off at higher speeds, so it's seen more use for upper stages. Ideally for a launch vehicle you would use a tripropellant design. That's how the space shuttle worked pretty much, it took off mostly on dense fuel solid rocket boosters, and then transitioned to liqhtweight liquid hydrogen fuel as the speed grew.

But even in rocketry, hydrogen is far from an ideal fuel, and it's even worse in vehicles like cars, and it would be an expensive fuel for aircraft.

[hamdani yusuf]

And they are charged by what magic? A typical filling station on an A road may have 10  or more pumps, each delivering 40 MW at roughly 20% duty cycle (a minute to deliver 50 liters, 3 minutes to pay, 1 minute to bring up the next car) so you need 80 MW average and 400 MW peak input to meet normal demand.

Sufficiently advanced technology is indistinguishable from magic. We can build solar panels or wind turbines with various design, which we will need anyway even if we go with green hydrogen.
The batteries at the charging stations are only used to reduce charging duration.

[Bored chemist]

Gas companies owned several "hydrogen mines"

Yes, but what we need are real hydrogen mines without the "quote marks".

[alancalverd]

The sea. Lots of it, all around the UK. Some of it even contains windmills to generate the subsidised electricity used to mine the hydrogen.

[alancalverd]

We can build solar panels or wind turbines

UK average solar input is 100 W/sq m so to recharge one electric car at a time at anything like a sensible rate,  you need at least 1000 square meters of garage roof space, plus sufficient battery storage to cope with the cars that arrive at night (up to 20 hours in the north of Scotland)  or when the wind  isn't blowing.

The real fun begins when there is a queue of battery cars at a single "pump". If each takes 40 minutes to refuel, it's probably quicker to walk. Fights will break out. The electric car is the beginning of the end of civilisation.

[Bored chemist]

The sea. Lots of it, all around the UK. Some of it even contains windmills to generate the subsidised electricity used to mine the hydrogen.

Sea water is not hydrogen; it doesn't burn with a characteristic squeaky pop.

[hamdani yusuf]

The real fun begins when there is a queue of battery cars at a single "pump". If each takes 40 minutes to refuel, it's probably quicker to walk. Fights will break out. The electric car is the beginning of the end of civilisation.

Or you can do it in your own garage over night. With 300 miles range, daily urban commute can last for a week. That's what the hydrogen car company claims in its website. But you are unlikely to refuel hydrogen car in your own garage.
Public charging stations are mostly needed for long journey only.

[walnutclose]

The real fun begins when there is a queue of battery cars at a single "pump". If each takes 40 minutes to refuel, it's probably quicker to walk. Fights will break out. The electric car is the beginning of the end of civilisation.

I find it interesting how little imagination folks have of how profoundly electric cars change the whole notion of refueling.    Personal vehicles are almost universally garaged or parked for 12 or more hours every day at the owner's residence.   Fleet vehicles used for trades, construction, farming, delivery and the like likewise at the owner's business.  They will be charged there, and leave "home" nearly every day fully charged.  They are only rarely driven more than 250 miles in a day.   Most will go months on end without needing to be recharged at a "station."   

[alancalverd]

The sea. Lots of it, all around the UK. Some of it even contains windmills to generate the subsidised electricity used to mine the hydrogen.

Sea water is not hydrogen; it doesn't burn with a characteristic squeaky pop.

Neither is ferric oxide the same as iron.  AFAIK the only substances that are mined as elements rather than compounds, are helium, carbon, and gold. It is a sin to burn carbon and the others don't oxidise readily. Every other element (including hydrogen) is extracted from its stable natural compounds when we need it.

[alancalverd]

Personal vehicles are almost universally garaged or parked for 12 or more hours every day at the owner's residence.

Apart from most of them, which are parked on the public road. You must have an idyllic suburban life in Walnut Close!

[Bored chemist]

The sea. Lots of it, all around the UK. Some of it even contains windmills to generate the subsidised electricity used to mine the hydrogen.

Sea water is not hydrogen; it doesn't burn with a characteristic squeaky pop.

Neither is ferric oxide the same as iron.  AFAIK the only substances that are mined as elements rather than compounds, are helium, carbon, and gold. It is a sin to burn carbon and the others don't oxidise readily. Every other element (including hydrogen) is extracted from its stable natural compounds when we need it.

If diesel oil was an element, you would have a point.

[alancalverd]

You still have to refine, extract and blend it from the gunge that comes out of an oil well. 

[Bored chemist]

You still have to refine, extract and blend it from the gunge that comes out of an oil well. 

Fundamentally; oil burns but water doesn't.

[walnutclose]

Apart from most of them, which are parked on the public road. You must have an idyllic suburban life in Walnut Close!

I do have an idyllic life, but not in the suburbs.   Walnut Close is a farm.   

But your "most" argument is wrong.   Two thirds of American households have covered, on site parking for their autos.   Another fraction beyond that 2/3 are able to park on their own property.   All of these households can, with modest upgrades to their infrastructure, overnite charge an electric vehicle. 

But in truth, these sort of arguments - energy density of hydrogen, at home charging - are not where the real discussion is needed.   Both electric and hydrogen are viable means of energy transmission and short term and mobile storage, and thus are viable fuels for transportation and heating (the only other area where people directly consume energy that is not already effectively electrified).  They present different engineering challenges, and different trade-offs to the consumer, but either can be made to work.

The real question is a system question - which is the better option (from a cost, efficiency, complexity and risk point of view) overall for source-to-consumption energy transmission and storage?   My sense is that hydrogen (compressed gaseous hydrogen that is) has only a relatively small role to play from that point of view.  Liquid hydrogen is too expensive (energy-wise) and complex to be useful for anything other than very specialized applications.

[hamdani yusuf]

A possible way Hydrogen can replace Lithium in a battery is as moving ion inside the battery. H+ has almost 7 times charge per mass ratio compared to Li+. But here we can't call Hydrogen as the fuel source, as we don't say Lithium as fuel source in Lithium ion battery.

We still need to choose/invent suitable materials for anode, cathode, electrolyte, and the separator, which comprise most weight of a battery cell, apart from the container.

[alancalverd]

Two thirds of American households have covered, on site parking for their autos.

Aha! A serious cultural difference. Probably 80% of UK private cars sleep at the roadside. We have a  higher outer-city population density (rows of terraced houses lining the sidewalk and maisonette apartments above shops)  and level of car ownership among city-dwellers, than you would find in the USA. Highest-density apartment blocks were generally not built with on-site parking for the present number of cars.

[alancalverd]

My sense is that hydrogen (compressed gaseous hydrogen that is) has only a relatively small role to play from that point of view. 

Again a cultural (and possibly generational) difference. The UK has an extensive gas grid, currently delivering  methane (most of which is used for generating electricity!)  to almost every home and factory. 60 years ago it carried "town gas", which was 50% hydrogen. The changeover was prompted by concerns of toxicity (most of the rest was carbon monoxide) and the availability of cheap methane from the North Sea, and was pretty well complete in 5 years. No problem in principle to convert to pure  hydrogen. 

[walnutclose]

No problem in principle to convert to pure  hydrogen. 

Other than if you're transporting like for like quantities of energy, you'll need to upgrade most of your lines to either bigger diameter or higher pressure pipes.   Hydrogen has roughly 1/4 the energy density of methane per unit volume at any given pressure.   (Not saying that as an objection - it's "just" a big civil engineering project).

[alancalverd]

But given the original mixture was 50% hydrogen the additional pressure requirement will be small. In any case the main feed pressure is a lot higher than the regulated  delivered flow to domestic gas taps - about 20 millibar. This happily delivers 50 kW to a commercial cooker through a 20 mm hose, so no problem recharging a car at a few megawatts from an adequately manageable 40 mm hose and a 500 mB pump - as they already do in several places in the UK.

[hamdani yusuf]

https://en.m.wikipedia.org/wiki/Hydrogen_vehicle
Most companies that had been testing hydrogen cars have switched to battery electric cars; Volkswagen has expressed that the technology has no future in the automotive space, mainly because a fuel cell electric vehicle consumes about three times more energy than a battery electric car for each mile driven. As of December 2020, there were 31,225 passenger FCEVs powered with hydrogen on the world's roads.[4]

As of 2019, 98% of hydrogen is produced by steam methane reforming, which emits carbon monoxide.[5]

If you think that you know better than those companies, it's an opportunity for you to create a start up in producing better hydrogen vehicles.