Hydrogen pilot abandoned

[fixitflav]

Look at the energy density of liquid hydrogen, and compressed hydrogen, try 1000PSI and 1000Bar, and compare those three numbers to petrol or diesel.
Then factor in the next level of loss being the weight of the container for the hydrogen and look at the net energy density. I cannot see how it makes any economic sense to even try.

The CV of hydrogen is about 137 MJ/kg, compared with 44 MJ/kg, about 35 MJ/litre, for petrol and diesel.
I don't think anybody's suggesting liquid hydrogen for road transport. Might be a case for trains or ships.
I believe compressed hydrogen for cars is at 700 bar, giving about 8 MJ/litre. A lot lower than petrol, but efficiency of a fuel cell is higher than an ICE, which helps.
But it isn't a case of comparing hydrogen with petrol and diesel, because if the government keeps to its threats, they will be banned. The comparison must be between hydrogen and other acceptable solutions, like battery electric.

 

[Mike13]

And liquid hydrogen is 70Kg per cubic metre, makes the internal volume of the tank quite a lot bigger to start with.
looking at compressed hydrogen:
Fuel cell will get about 2x efficiency of a diesel, or about 3x a petrol engine, so for a similar driving range the inside of a 700 bar tank has to be 75 % larger than the petrol tank. So for a larger car we need a 100+ litre bomb in the boot... and that adds an extra 150+Kg to the weight of the car.

 

[robinbanks]

Let's suppose you had a magic device that, once built, produced electricity at zero cost and needed no fuel.

Are you on a "wind" up?

 

[fixitflav]

And liquid hydrogen is 70Kg per cubic metre, makes the internal volume of the tank quite a lot bigger to start with.
looking at compressed hydrogen:

That's right. But with CV ~ 3x and efficiency say 2.5x, it's equivalent to about 500 kg/m^3, still not up to petrol and diesel. In any case, as I said, I don't think liquid hydrogen is being considered for cars.

for a similar driving range the inside of a 700 bar tank has to be 75 % larger than the petrol tank. So for a larger car we need a 100+ litre bomb in the boot... and that adds an extra 150+Kg to the weight of the car.

Agreed, and being pressurised, the tank can't be a shape to fit conveniently into a car body. There's plenty of downsides with hydrogen, and it wouldn't get a look in if ICEs weren't being forced out.