Hydrogen vs. Battery

[jkn]

If you can't be bothered to make a real analysis, then please refrain from reaching any conclusions. This is the kind of ignorance that leads to anti vaccination hysteria, radical anti nuclear insanity and other ignorant positions radical environmentalist zealots take.
Without proper quantitative analysis of the REAL impact of such an engine/aircraft, you cannot reach any conclusion, except the extreme zealotry one. Please stop and think.
Ozone is produced naturally continuously. The problem with CFCs is those molecules destroyed O3 non stop and stayed there for a long time. If 1000 lapcats flying at 80000ft all year around consume 0.1%/year of O3 layer then its a non issue, if it consumes 10%/year then its an actual issue.
Leave that job for the actual PhDs in the proper area to study.
BTW it IS being studied:
LAPCAT II

My conclusion is and was: Flying in ozone layer will cause problems. If those problems are only political, requires a study. Effects of water in that altitude needs to be studied.

LAPCAT WAS studied:
LAPCAT - Wikipedia
LAPCAT II, a 10 million euro, four-year, follow on project, started in October 2008.


I strongly suspect energy efficiency of hypersonic flight is good enough for practical use. Skipping out of atmosphere might help, but it is not a practical idea. In those speeds surface of frame of the plane gets very hot. I don't know if it would be red hot, but close.

 

[FutureShock]

The inevitable being realized Audi on fuel cells: Maybe later

Great quote in that article. It refers to Audi, but really could apply to the entire auto industry in general:

"The worst thing you can do is kind of half-bake electric, then go off on another science project with fuel cells, then go running to another science project," Scott Keogh, President of Audi of America, told Automotive News on the sidelines of the Frankfurt auto show.

.

 

[Saghost]

I strongly suspect energy efficiency of hypersonic flight is good enough for practical use. Skipping out of atmosphere might help, but it is not a practical idea. In those speeds surface of frame of the plane gets very hot. I don't know if it would be red hot, but close.

That's problem you have to deal with even at hypersonic (or even high supersonic) speeds. Finding hard numbers online is being challenging right now, but both the SR-71 and the X-15 had to deal with temperatures in the 800-1000F range at noses and wing leading edges.

 

[Jeff N]

"The worst thing you can do is kind of half-bake electric, then go off on another science project with fuel cells, then go running to another science project," Scott Keogh, President of Audi of America, told Automotive News on the sidelines of the Frankfurt auto show.

This is consistent with VW's ElectrifyAmerica (name hint) subsidiary declining to spend any of their first 2.5 year round of their 10-year $2 billion Dieselgate settlement infrastructure money on H2 fueling facilities.

 

[voyager]

"The worst thing you can do is kind of half-bake electric, then go off on another science project with fuel cells, then go running to another science project," Scott Keogh, President of Audi of America, told Automotive News on the sidelines of the Frankfurt auto show.

.

TTAC also picked up the comments on hydrogen.
"You end up with a well to wheel efficiency of roughly 30 percent for hydrogen, as opposed to more or less well to wheel 70 percent efficiency for a battery electric vehicle,” explained Ziebart (Jaguar Land Rover’s technical design director). “So the efficiency of putting the electric energy directly into a battery is about twice as high as the efficiency of producing and using hydrogen.”

Further Proof That Hydrogen Cars Are Stupid

 

[Doug_G]

We're still talking about hydrogen?

 

[FutureShock]

We're still talking about hydrogen?

What's the name of the thread?

If you're talking about in general, as in why is hydrogen still being pushed by some as THE big alternative to ICEs, despite the considerable drawbacks... then yeah, you got me.

.

 

[GoTslaGo]

Well there's one interesting transport experiment using Hydrogen Fuel Cells (as a component) going on right now:

PORT OF CALL N°4 Nantes from 9 to 17 september

 

[dpeilow]

Found a motherload of information here:

http://www.phaedrus-project.eu/userdata/file/Public deliverables/PH-D1.1-Report on fuelling system requirements and targets for capex and opex.pdf

https://www.sintef.no/globalassets/project/novel/pdf/presentations/03-07_hyet_bouwmann_public.pdf


This is a project that was demonstrating the use of electrochemical compressors rather than mechanical compressors to take the hydrogen output from the electrolyser up to 800 bar (for filling 700 bar cars with the necessary pressure differential). This is claimed to be the most efficient way to do it.

They claim 4 kWh / kg to compress but their own graph shows 6 kWh / kg minimum is needed to go to 800 bar...

 

[RubberToe]

We're still talking about hydrogen?

Well, it is on topic at least!

RT

 

[ItsNotAboutTheMoney]

We're still talking about hydrogen?

Until such time as there's a realistic plan for clean, 100% renewable energy system that can handle all energy needs, it's not going to stop.

 

[scaesare]

Found a motherload of information here:

http://www.phaedrus-project.eu/userdata/file/Public deliverables/PH-D1.1-Report on fuelling system requirements and targets for capex and opex.pdf

https://www.sintef.no/globalassets/project/novel/pdf/presentations/03-07_hyet_bouwmann_public.pdf


This is a project that was demonstrating the use of electrochemical compressors rather than mechanical compressors to take the hydrogen output from the fuel cell up to 800 bar (for filling 700 bar cars with the necessary pressure differential). This is claimed to be the most efficient way to do it.

They claim 4 kWh / kg to compress but their own graph shows 6 kWh / kg minimum is needed to go to 800 bar...

So if we pick the middle, and assume it's 5KWh/kg that's an energy cost of roughly 20 miles worth of EV driving to compress a Kg of H2.

A quick google search suggest 70 miles of range per Kg is reasonable for an H2 car. So that's a 29% penalty for compression alone.

 

[dpeilow]

A quick google search suggest 70 miles of range per Kg is reasonable for an H2 car

Actually Autocar magazine in the UK reported a real world economy of 45 miles per kg for the Toyota Mirai. Hyundai quotes an EPA figure of 47 miles per kg for the Tuscon.


What's also quite amazing in that report I linked is the way the efficiency for these electrolysers drops off as they age. They show that the End of Life system efficiency could be as bad as 81.7 kWh/kg - and remember this is coming from the consortium doing the project, led here by Shell. That is *way* higher than anything I ever saw before in the promo material.

Also apparent from the text is they design the station for two refuelings per hour.

 

[scaesare]

Actually Autocar magazine in the UK reported a real world economy of 45 miles per kg for the Toyota Mirai. Hyundai quotes an EPA figure of 47 miles per kg for the Tuscon.

Oof.

Thanks for the more real-world numbers. That makes the compression along more like a 45% energy hit.

 

[Doug_G]

Speaking of cars powered by compressed gasses... here's what happens when an LPG tank blows:

(Oh and the comments are hilarious.)

 

[ohmman]

(Oh and the comments are hilarious.)

Only a very brave individual would venture into the horror that is the YouTube comment feed.

 

[dpeilow]

Hydrogen is the future, not battery-electric cars: Lexus | CarAdvice

 

[Blu Zap]

Remember the Hindenburg.

 

[dpeilow]

I was looking into Toyota's tanks and fuel cell, both of which they say are #1 for energy density.

Toyota says the Mirai tanks are 5.7% hydrogen by total weight. Most others are 5.5 or 5.4. It doesn't sound much but for 1 kg of hydrogen it means the difference between a 16.5 kg tank and 17.5 kg tank.

I found some details on the tanks in the SAE paper here Development of High-Pressure Hydrogen Storage System for the Toyota “Mirai” (you can get info from the preview but if anyone can get the whole paper and check that would be handy).

Now, if they are at 5.7% then with those tank weights they would need 5.25 kg of H2, but to fit that into the 122.4 litre capacity it needs to be at 800 bar.

However, the car and filling stations are rated for 700 bar (nominal working pressure 70 MPa, above). They do say that 800 bar is used by the filling stations to create a pressure differential to get the H2 to flow into the car (e.g. I've seen that in the literature of the pump manufacturers), and the tank itself has a max safe fill pressure of 875 bar, but that is not what the pumps are supposed to fill to.

If I work out the weight of hydrogen that 122.4 litres can hold at 700 bar, it's 4.8 kg. So that's hydrogen by total weight of 5.2%. It's almost 10% less hydrogen.


So now I wonder whether the EPA rating is done at 800 bar or 700 bar. If the former, it would explain why Autocar got a much lower real world range number on their test.


Anyone care to check my calculations?

 

[jkn]

That's problem you have to deal with even at hypersonic (or even high supersonic) speeds. Finding hard numbers online is being challenging right now, but both the SR-71 and the X-15 had to deal with temperatures in the 800-1000F range at noses and wing leading edges.

I saw a video of the X-15 after record flight. Small details in its frame had started to melt! Yes we can(?) deal it, but it is not energy efficient. I guess everyone has seen Elons passenger rocket concept (idea is old). In long distance that is surprisingly energy efficient. (Raptor burns 3.5 kg oxygen for every kg of methane.) Hydrogen is best rocket fuel, if we ignore fuel tank size. Perhaps carbon nanotubes will make hydrogen popular in future.