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0 pointsraxxorrax7y ago0 comments

I still think there is a limit in chemical density that cannot be overcome without significantly changing technological principles of current batteries. Maybe hydrogen fuel cells would be a better solution after all if we can find an efficient way to contain it. Easier said than done...

0 comments

18 comments · 2 top-level

gambiting7y ago· 15 in thread

Energy density of hydrogen per litre is few orders of magnitude lower than that of petrol. Really the only saving grace of hydrogen vs batteries is the speed of refueling.

chadcmulligan7y ago

If someone invented a cheap round trip processing method CO2 -> petrol then EV's would have a hard time I suspect

kozak7y ago

But we would still need batteries to store regenerative braking energy (i.e. it would be a hybrid).

2 more replies

clouddrover7y ago

Here are two such efforts:

https://carbonengineering.com/

https://www.prometheusfuels.com/

cinquemb7y ago

I think molten salt (latent heat) batteries could push the boundaries further as researchers continue to design salt mixtures with lower melting points and higher and higher delta_k's (economic considerations of compounds included).

Though for usage in cars would imply some kind of small/portable vacuum storage tanks and a way to put the heat to work (most likely initially through a steam engine and eventually directly to electricity via advanced thermocouples[0])

[0] https://arxiv.org/abs/1308.5935

clouddrover7y ago

> Really the only saving grace of hydrogen vs batteries is the speed of refueling.

And range, weight, and (eventually) price. Batteries need to improve in all these areas.

Fuel cell cars are expensive at the moment because they're produced in such low volumes. But Toyota thinks that if they produced FCEVs at scale they could build them cheap:

https://www.thedrive.com/tech/26050/exclusive-toyota-hydroge...

magduf7y ago

Toyota is the only company pushing hydrogen as a fuel for cars, and it's puzzling why, because they really don't have many advantages, and a ton of disadvantages compared to BEVs.

Everyone else is working on BEVs, including the Chinese.

1 more reply

snakeboy7y ago

Am I misreading the gp's cited chart? According to that, it seems like hydrogen is only a factor of around 4x worse in terms of volumetric energy density, and is better than petrol in weight density.

magduf7y ago

Weight density doesn't help you in a car; these aren't rockets where most of the weight of the vehicle is fuel. In a car, the weight of the fuel is barely noticeable. What's much more important is the size of the tank, and a hydrogen tank takes up a lot of room (to get decent range), and is also quite heavy to contain a pressurized gas that literally leaks out constantly because its molecules are so small.

namibj7y ago

Weight density is better. Nothing else comes really close. The volumetric missmatch could be right.

imtringued7y ago

And you can always refine it into methane for an even higher density.

raxxorraxOP7y ago

Still better than current batteries. You could pump that up if you store it in a liquid state to a level above common fossil fuels. Not saying you don't open a can of worms for implementing it...

gambiting7y ago

Hydrogen in liquid state leaks out of any container that you put it in. 70kg lead bottle stores only 1L of hydrogen and all of it evaporates naturally in 1-2 months through the metal. So no, storage of liquid hydrogen is a terrible idea.

1 more reply

magduf7y ago

Besides in-vehicle storage being completely infeasible for many reasons, how exactly do you propose to safely allow consumers to refill a tank with liquid hydrogen? They use it for rockets sometimes, but it's handled very carefully by highly trained technicians under very controlled conditions and the fueling procedure is nothing like a stop at your local gas station.

make37y ago

isn't it still much better than batteries?

LifeLiverTransp7y ago

Dont you forget something- hydrogen if hydrolizes takes place in situa - aka directly below a windpower or solar-plant, has the lowest conversion loss right there.. Also storage can be improved by now chemically - meaning you bind it to a https://en.wikipedia.org/wiki/Hydrogen_storage#Liquid_organi...

and reduce that to a nearly solid material with extremly high energy density. Its okay to be a tesla fanboi, its not okay to propagate ancient technological "insights".

pjc507y ago· 1 in thread

To me, there's not so much difference between batteries and fuel cells - one stores the redox reaction components outside the electrode/electrolyte setup, that's all. The advantage of hydrogen in this setup is the ability to pull oxygen from the air and then dump the reaction product.

raxxorraxOP7y ago

Depending on the process of extracting hydrogen, it could also be more environmental friendly overall. I don't know much about the battery life cycle, but I image there to be "casualties".

I know there are many, many problems to solve for fuel cells and if you are scared of some burning batteries, this solution probably doesn't provide much consolation.

j / k navigate · click thread line to collapse

0 comments

18 comments · 2 top-level

gambiting7y ago· 15 in thread

Energy density of hydrogen per litre is few orders of magnitude lower than that of petrol. Really the only saving grace of hydrogen vs batteries is the speed of refueling.

chadcmulligan7y ago

If someone invented a cheap round trip processing method CO2 -> petrol then EV's would have a hard time I suspect

kozak7y ago

But we would still need batteries to store regenerative braking energy (i.e. it would be a hybrid).

2 more replies

clouddrover7y ago

Here are two such efforts:

https://carbonengineering.com/

https://www.prometheusfuels.com/

cinquemb7y ago

[0] https://arxiv.org/abs/1308.5935

clouddrover7y ago

> Really the only saving grace of hydrogen vs batteries is the speed of refueling.

And range, weight, and (eventually) price. Batteries need to improve in all these areas.

Fuel cell cars are expensive at the moment because they're produced in such low volumes. But Toyota thinks that if they produced FCEVs at scale they could build them cheap:

https://www.thedrive.com/tech/26050/exclusive-toyota-hydroge...

magduf7y ago

Toyota is the only company pushing hydrogen as a fuel for cars, and it's puzzling why, because they really don't have many advantages, and a ton of disadvantages compared to BEVs.

Everyone else is working on BEVs, including the Chinese.

1 more reply

snakeboy7y ago

Am I misreading the gp's cited chart? According to that, it seems like hydrogen is only a factor of around 4x worse in terms of volumetric energy density, and is better than petrol in weight density.

magduf7y ago

namibj7y ago

Weight density is better. Nothing else comes really close. The volumetric missmatch could be right.

imtringued7y ago

And you can always refine it into methane for an even higher density.

raxxorraxOP7y ago

Still better than current batteries. You could pump that up if you store it in a liquid state to a level above common fossil fuels. Not saying you don't open a can of worms for implementing it...

gambiting7y ago

1 more reply

magduf7y ago

make37y ago

isn't it still much better than batteries?

LifeLiverTransp7y ago

and reduce that to a nearly solid material with extremly high energy density. Its okay to be a tesla fanboi, its not okay to propagate ancient technological "insights".

pjc507y ago· 1 in thread

raxxorraxOP7y ago

Depending on the process of extracting hydrogen, it could also be more environmental friendly overall. I don't know much about the battery life cycle, but I image there to be "casualties".

I know there are many, many problems to solve for fuel cells and if you are scared of some burning batteries, this solution probably doesn't provide much consolation.

j / k navigate · click thread line to collapse