Nah, his idea doesn't violate the 2nd law of thermodynamics. Yours is much more interesting.
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Toyota 'Mirai' Fuel Cell Sedan
- Thread starter ivog
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Nah, his idea doesn't violate the 2nd law of thermodynamics. Yours is much more interesting.
I do agree that the best case for H2 is as a plug-in hybrid. I still think that the investment you need to make in filling stations is too much and it doesn't work.
A FC car with a 50 mile EV range will probably end up needing to do at least 25% of its refueling at H2 stations. ( The Volt does 37% of its refueling at gas stations. )
So you've reduced the cost of the H2 stations you need by a factor of 4. But the H2 stations start out somewhere between 20x and 100x more expensive than building a supercharger network.
The problem with a niche product with a niche set of uses is that it still needs a fully fleshed out refueling network or its horribly inconvenient.
adiggs
Well-Known Member
I still think that I don't want to be within 3 city blocks of a vehicle with hydrogen gas under pressure in it, at any time, for any reason. I don't want to see an FCEV show up in the parking lot at work.
And I really don't want to see the "Hydrogen Vehicles are Dangerous" thread show up here on the forums, and then start getting periodic updates. I realize they've put a lot of energy into how to have catastrophic failures of the tank "safely". That will minimize the number of events. It can't eliminate them, and the failures - when they come - won't be like the Tesla fires that so occupied the media. But hey - under "if it bleeds it leads", each one of those events will get lots of press that should do a nice job of slowing adoption (if all the other impediments to adoption doesn't do the trick).
And I really don't want to see the "Hydrogen Vehicles are Dangerous" thread show up here on the forums, and then start getting periodic updates. I realize they've put a lot of energy into how to have catastrophic failures of the tank "safely". That will minimize the number of events. It can't eliminate them, and the failures - when they come - won't be like the Tesla fires that so occupied the media. But hey - under "if it bleeds it leads", each one of those events will get lots of press that should do a nice job of slowing adoption (if all the other impediments to adoption doesn't do the trick).
I was considerably closer to THIS event than 3 city blocks when it occurred. Fortunately I was at work when it happened. It was caused by a very slowly leaking propane Taxi parked overnight beneath the three store townhouses/condos. (garage space was on one level, and was in common with all the units) It was caused by someone flipping on a light switch in the garage that morning. Fortunately it was only propane and not hydrogen.
Apartment Building Explodes in Ottawa, 1 Killed
Put me right off compressed gas vehicle conversions, and my then current car was due to be 'dual-fueled' converted to gasoline/propane. We had a sudden fancy for them in Canada around this time, mostly propane singles (mostly taxis and local delivery trucks) with some dual gasoline/propane dual fuels, and some factory built natural gas single fuels (Ford cars)
Yes, they are rare. Trouble is, when they DO happen, they tend to be catastrophic.
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I doubt that would happen with hydrogen. That stuff is so hard to contain that you wouldn't get any kind of build up (which is part of the stupidity of trying to use it). Also, since the fuel cell doesn't generate as much heat, you couldn't get ignition from the heat of a running vehicle, which has been the cause of other explosions. But if as much money were spent on the fuel system as in current HFCVs, I'd bet there'd be fewer explosions.
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adiggs
Well-Known Member
Here's the paper / study of a hydrogen explosion event that I read:
http://conference.ing.unipi.it/ichs2005/Papers/100096.pdf
It's worth reading. A few big takeaways for me:
- we use hydrogen under pressure for a variety of important industrial reasons
- those situations are effectively ALL static / immobile
- the safety gear to make them safe is big and heavy
- AND we only have a few kg of hydrogen under pressure at a time anyway (make it and use it immediately)
- about the same amount of hydrogen the fuel cell folks are proposing we put into a mobile package and drive around with all the time
- hydrogen is scary stuff
If you don't read the whole paper - the abstract is worth reading. One bit not in the paper - my understanding is that the 5-7 kg of hydrogen and it's pressure in this explosion is the right order of magnitude and pressure for an fcev.
stopcrazypp
Well-Known Member
While it may leak relatively quicker than other gases, I don't think it is true that hydrogen doesn't build up. That is the reason why hydrogen station roofs are required to be designed such that there is no chance for it to collect (the underside slopes upward). As pointed out by Doug_G, the Fukushima incident had explosions from hydrogen build-up.
I disagree.
If you're going to make a range extended BEV where you're using efficient battery power 90%+ of the time, and only using the range extender to be a convenient way to refuel while on a long distance trip, why would you make the range extender an expensive fuel cell that is far more difficult to refuel than a gasoline engine? Add to that that the Chevy Volt has similar greenhouse emissions running on gasoline than the Mirai does running on Hydrogen, and really, what the heck is the point?
a) efficiency, the fuel cell stack outputs DC and can directly drive the motors and/or recharge the batteries, so fewer components involved in a FC-PHEV vs. EREV.
b) net-zero emissions for those who can source their H2 from electrolysis and wind/solar energy.
Maybe it's not worth the development dollars, but it sure offers a more viable successor to the Mirai.
Perhaps fewer components, but not lower cost.
and gasoline engines have had decades to work out their issues.
Net-zero emissions is a lie in today's electricity market.
If you have a surplus of electricity, you should put it on the grid so that the natural gas plant down the street doesn't need to burn it to power your neighbor's house. You should then buy hydrogen produced through steam reformation of natural gas, which is much more efficient than wasting clean electricity to split water.
Any time someone tells me that they have a thought of using clean electricity to split water, I shake my head:
If you have 60 kWh of electricity and you put it on a grid using natural gas, you can save 600 cubic feet of natural gas from being burned.
If you have 60 kWh of electricity and you use it to split water, you can make 1 kg of hydrogen.
If you take 200 cubic feet of natural gas and steam reform it, you can make about 1 kg of hydrogen.
So for every kg that you make with electrolysis instead of steam reformation, you're causing the world to burn some 400 extra cubic feet of natural gas, just so that you can say that you used "clean energy" to power your car.
Equivalently, a HFCV using steam reformed hydrogen emits about as much carbon as a 35 mpg car. (better than most gasoline cars, but not as good as a Prius). A HFCV using hydrogen from electrolysis is causing the world to emit as much carbon as a 12 mpg car. and it does NOT matter if it came from your roof: electricity is electricity, and it's easily shipped over power lines. If your wind turbine produces electricity, putting it on the grid will mean less natural gas needs to be burned than if you put your clean power into your HFCV.
So, no, I really don't see any point to a HFCV range extender; gasoline works perfectly well for that application.
To the argument that a BEV with a HFCV range extender makes more sense than a HFCV alone, well maybe, but that's only because the more your car is a BEV and the less your car is an HFCV, the better it is. You know what would be even better than a BEV with a HFCV range extender? a pure BEV made by Tesla.
I am pretty sure that this is the basic concept of a Fuel cell powered vehicle. It should work perfect in a P85D since the rear motor is bigger than the front. perpetually perfect!
(sadly and engineer honestly asked my why the car didn't have a generator to gain power while the car drove, not referring to regen upon slowing- he might work at Toyota now?)
If you have an EREV with sufficient AER, then the average reduction in fuel could be enough to allow the remainder to use biofuels and synfuels. Given regular gas is typically 10% ethanol, you'd need to replace 93 1/3 % of gasoline with electric and you'd theoretically be able to power gasoline transportation just with current ethanol fuel production. With a combination of BEV and EREV that could be done.
I feel that in any renewable system biofuels and synfuels will be essential to meet the need for high density fuel.
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I was thinking more along the lines of fewer components = lighter weight. The lower cost is a matter of design iterations. As you've said, gas engines have had decades to work this through.
When I said, net-zero emissions, I wasn't talking about now with our current supply of electricity. With many places targeting 100% renewable energy in their future, at some point, they'll have enough solar/wind to crash the local energy market and need ways to time-shift their available energy. And those places won't be looking to maintain a full NG power plant to provide power for the few days of the year when it's both cloudy and still.
Now if you can synthesize methane with CO2 and the extra energy from solar/wind, then that would make it net-zero as well, with far fewer storage issues, but I haven't seen anyone working on this and methane mucks up fuel cell stacks, so am stuck with H2 from electrolysis.
Edit: Just realized you can burn methane to run your range extender. But still need a method to synthesize it first.
JohnSnowNW
Active Member
Are they even within the same physical dimensions? I thought the mirai was categorized as a mid-sized sedan? Why not compare the model S weight to the Mirai, while you're at it?
Comparing an ICE range extender (+ generator, transmission, and fuel tank) to a fuel cell stack (+ inverter, and H2 tank) should be somewhat favorable.
The Mirai is about the same size as a Camry hybrid and weighs 600lbs more. Adding batteries to make the Mirai a plug-in vehicle would add the same weight that adding batteries to make the Camry a plug-in vehicle would.
Seems like a reasonable approach.
A complete Volt pack, largest of the plug in hybrids, is 435 pounds - with five year old technology. The Camry already has a hundred pound battery pack (245V NiMH) and the only other thing you'd need is a charger module.
Thus, the weight impact on the Camry (or presumably the Mirai) should be on the order of ~350 pounds in principle.
Walter
JohnSnowNW
Active Member
It's not exactly like I'm comparing a mid-sized sedan to a sub-compact here. I chose the Volt because it has the largest battery pack of any EREV Sedan (GMs designation). The Mirai's wheelbase is only 4" larger.
The point was that hydrogen powered vehicles are not light.
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