New Energy Vehicles (NEVs) in China


Nutrient

Junior Member
Registered Member
I think Hydrogen is a dead end. Maybe its because I have watched so many engineers say that, that it has many disadvantages compared to electric.

Hydrogen needs to be taken from natural gas.
It consumes energy to convert natural gas to hydrogen.


No, natural gas is not an absolute necessity for making hydrogen -- it is just the currently most convenient method, as the gas pipelines have already been built.

You can also get hydrogen by electrolyzing water, using electricty from solar panels. Yes, as Elon Musk says, this is less efficient than putting the electricity directly into batteries, but solar farms can generate so much energy during the day that we can afford to waste some.

Hydrogen is portable energy, far more portable than batteries. The best Lithium batteries are at 250 watts/kg, and Hydrogen is like 38,000 watts/kg, over 100 times better. So hydrogen is great for larger vehicles like trucks, ships, airplanes, and so on.

Note that I said "larger". Hydrogen's biggest problem is its very low density: it liquifies at ultra-low temperatures (-269 C), which makes liquid hydrogen impractical for everyday use (it's great for rockets though). You could combine the hydrogen with something else to make a liquid (like methanol), but then you would have to get the hydrogen out again, and that wastes energy. So you need a large tank to hold the gas, which means large vehicles like trucks, ships, etc.

Or you could compress the hydrogen for use in passenger cars. The Toyota Mirai, for example, uses tanks containing 700 atmospheres. That makes me nervous: so much pressure is like a bomb waiting to explode. Toyota reassures everyone that their tanks are strong enough, but I am not so sure.

So for the moment, hydrogen is for the larger vehicles like trucks or ships, or maybe even airplanes.
 

FairAndUnbiased

Junior Member
Registered Member
No, natural gas is not an absolute necessity for making hydrogen -- it is just the currently most convenient method, as the gas pipelines have already been built.

You can also get hydrogen by electrolyzing water, using electricty from solar panels. Yes, as Elon Musk says, this is less efficient than putting the electricity directly into batteries, but solar farms can generate so much energy during the day that we can afford to waste some.

Hydrogen is portable energy, far more portable than batteries. The best Lithium batteries are at 250 watts/kg, and Hydrogen is like 38,000 watts/kg, over 100 times better. So hydrogen is great for larger vehicles like trucks, ships, airplanes, and so on.

Note that I said "larger". Hydrogen's biggest problem is its very low density: it liquifies at ultra-low temperatures (-269 C), which makes liquid hydrogen impractical for everyday use (it's great for rockets though). You could combine the hydrogen with something else to make a liquid (like methanol), but then you would have to get the hydrogen out again, and that wastes energy. So you need a large tank to hold the gas, which means large vehicles like trucks, ships, etc.

Or you could compress the hydrogen for use in passenger cars. The Toyota Mirai, for example, uses tanks containing 700 atmospheres. That makes me nervous: so much pressure is like a bomb waiting to explode. Toyota reassures everyone that their tanks are strong enough, but I am not so sure.

So for the moment, hydrogen is for the larger vehicles like trucks or ships, or maybe even airplanes.
You don't need to get hydrogen out of methanol. You can burn it directly. You can also reform hydrogen into natural gas if the hydrogen is obtained from renewables.
 

AssassinsMace

Lieutenant General
What changes the game for hydrogen cars is when you can fill up your tank with water is where you get the hydrogen from. I remember long ago that was the pitch for hydrogen cars. I don't know if that was unrealistic but by watching that video they aren't even anywhere close to that.
 

Nutrient

Junior Member
Registered Member
You don't need to get hydrogen out of methanol. You can burn it directly.
Yes, you could burn the methanol directly. But methanol (CH3-OH) has carbon in it. Are there any scalable sources of renewable carbon? (There's a reason the English switched to coal: they probably preferred to burn wood, but their forests were almost gone.) Getting carbon from the atmosphere is impractically slow: I believe I said upthread that carbon dioxide is 0.04% of air.


You can also reform hydrogen into natural gas if the hydrogen is obtained from renewables.
Natural gas is methane (CH4). So it's the same problem: a scalable source of renewable carbon.
 
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