Are Fuel Cells a Viable Alternative to Batteries Given Their Challenges?

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http://img301.imageshack.us/img301/857/800pxwasserstoffeinfc3b.jpg

 

[mgb_phys]

Also from the same company as the BMW system.
Uses H2 fuel cells instead of batteries and regenerates H2/O2 at sea from diesels .

 

[mheslep]

Also see previous threads
https://www.physicsforums.com/showthread.php?t=276757&referrerid=70823"
https://www.physicsforums.com/showthread.php?t=204457&referrerid=70823"
and
http://www.rsc.org/images/NEWS-p14-395_tcm18-99997.jpg

 

[mheslep]

(Liquid hydrogen has about 1/2 the BTU content of gasoline.)

Yes and no. Liquid H2 has a 3x greater energy density by weight (143MJ/kg) than gasoline (47MJ/kg), but a 1/3 lower volumetric density (10 MJ/L vs 34MJ/L). Typically the addition of an impact resistant cryogenic tank eats away the weight advantage. Of course if a spacecraft is the goal, where a weight is mostly the only concern then one can't beat liquid H2 for a fuel / energy carrier / whatever.

 

[Phrak]

Take out the back seat, and install a tank good for a 120 mile range. That's 1% of a compromise dsolution.

That tank wouldn't fit in the 'skateboard' chassis so excitedly promoted on the Planet Green channel. Why is that? But, then again, they were talking about perpetual motion automobiles last Sunday.

 

[mgb_phys]

Take out the back seat, and install a tank good for a 120 mile range. That's 1% of a compromise dsolution.

They are covering their backs in case someone somewhere demands a mandatory % of ZEV in your lineup. BMW are feeling nervous as a maker of large high performance cars.

BMW are also partnering with Fiat to produce a range of small electric cars (BMW make the new 'mini' - which isn't very mini and Fiat make the new Fiat 500 which is a 1300)

 

[mheslep]

This H vs Batteries efficiency chart ought to be at the top of all threads like this, a sticky perhaps.

http://www.physorg.com/news85074285.html

 

[Topher925]

Take out the back seat, and install a tank good for a 120 mile range. That's 1% of a compromise dsolution.

You need to stop using asinine and completely obsolete facts to support your arguments. I don't think anyone believes BMW's concepts to go anywhere, not even them. As I already stated the Honda Clarity gets 280 miles for 4 kg of H2 and has a normally size back seat. As already mentioned H2 does require larger volumes of space but has about 3 times the energy density which is what really matters for most fuels.

This H vs Batteries efficiency chart ought to be at the top of all threads like this, a sticky perhaps.

Nice chart but we all know that batteries have a more efficient operation process than fuel cells. And where does the 80% for trasport/transfer come from? I'm calling shenanigans on that. That graph is also missing a discharge efficiency for the battery as well.

The advantages of fuel cells aren't that they are more efficient, its that they have the possibility to be more economic, environmentally friendly, and allow vehicles to be refueled and not recharged.

 

[mheslep]

...Nice chart but we all know that batteries have a more efficient operation process than fuel cells. And where does the 80% for trasport/transfer come from? I'm calling shenanigans on that

The answer is straightforward. How do you expect to get the H2 -compressed or liquified - to Topher's H2 refueling station? The answer is you will burn up, on average, 20% of the equivalent energy of the fuel payload in transportation energy. It requires on the order of a dozen tanker loads of H2 to bring the energy contained in one tanker load of gasoline. Details are in Bossel's paper as alluded to in the link.

That graph is also missing a discharge efficiency for the battery as well.

That's small and covered in the 90% EV block.

The advantages of fuel cells aren't that they are more efficient, its that they have the possibility to be more economic, environmentally friendly, and allow vehicles to be refueled and not recharged.

Efficiency largely equates to economics, especially when the topic is energy. Emissions is a wash with either fuel cell or batteries. Refueling vs charging time and vehicle range are the advantages of the fuel cell, and they're important, maybe critical. It is certainly not economics, even looking solely at the vehicle. If one assumes a centralized H2 infrastructure the economic comparison is no longer in the same ball park (distributed, i.e. localized H2 production might work).

 

[Topher925]

The answer is straightforward. How do you expect to get the H2 -compressed or liquified - to Topher's H2 refueling station? The answer is you will burn up, on average, 20% of the equivalent energy of the fuel payload in transportation energy. It requires on the order of a dozen tanker loads of H2 to bring the energy contained in one tanker load of gasoline. Details are in Bossel's paper as alluded to in the link.

Your answer is miss guided. Many hydrogen refueling stations manufacture H2 on sight or refilled by near by sources and produce it in accordance with demand. H2 isn't dug up out in Saudi Arabia and shipped over to refueling stations like gasoline. There is no reason why you couldn't have your FCV produce H2 at home either.
http://www.fuelcells.org/info/charts/h2fuelingstations.pdf

That's small and covered in the 90% EV block.

No it isn't. Discharge efficiencies are not small, that's why battery arrays in BEVs have such elaborate cooling systems. Cooling is actually one of the major road blocks for the development of the Chevy Volt and I believe is still a problem for the Tesla roadster (which keep in mind ended up being a failure). Bossol's statement about 80% cycle efficiency is true if you are operating a battery under ideal conditions. With the discharge rates that cars demand (even NiMH hybrids) I think you would be rather hard pressed to find a cycle that efficient. This isn't even including self discharging. I believe there were some very good rebuttals to that IEEE paper as well, I'll try to dig them up.

Efficiency largely equates to economics, especially when the topic is energy.

Is this why gasoline cars are so much cheaper than electric ones?

Emissions is a wash with either fuel cell or batteries.

Not necessarily. An electric cars battery needs to be replaced and recycled several times (with current tech) during the cars life cycle. As I am sure everyone knows, lithium chemistry based batteries aren't cheap to recycle and can do some serious damage if just disposed of in the environment. Electric cars may be 0 emission in the long run but it comes with a big price tag. The #1 ingredient for fuel cells however is plain old carbon, and contains no toxic chemicals.

It is certainly not economics, even looking solely at the vehicle. If one assumes a centralized H2 infrastructure the economic comparison is no longer in the same ball park (distributed, i.e. localized H2 production might work).

And how would you know this? I refer you to an article I previously posted up above. Even a highly educated guess about economics at this point is still almost fantasy.

 

[mheslep]

Your answer is miss guided. Many hydrogen refueling stations manufacture H2 on sight or refilled by near by sources and produce it in accordance with demand. H2 isn't dug up out in Saudi Arabia and shipped over to refueling stations like gasoline.

Actually, that's exactly how the vast majority of H2 is currently produced (95%) - by reforming natural gas. Electrolysis doesn't compete with reforming NG. Those stations are demos, they are not practical.
http://www1.eere.energy.gov/hydrogenandfuelcells/production/natural_gas.html

There is no reason why you couldn't have your FCV produce H2 at home either.

Practically a home setup would have to be quite elaborate: electrolysis gear, a heavy home power hookup (~40kw for 5kg H2 in 5 hours), 5kpsi compressor and on site storage for compressed H2.

http://www.fuelcells.org/info/charts/h2fuelingstations.pdf

12kg H2 storage? 10 cars per day and so on? A 'big' 20 car/d station is using an internal combustion engine generator to to make the electrolysis power. I've seen the list, they are all demos. Bossel shows a real, 1000 car/day station would need a 30MW electrical service and 110M^3 water per day.

No it isn't. Discharge efficiencies are not small, that's why battery arrays in BEVs have such elaborate cooling systems. Cooling is actually one of the major road blocks for the development of the Chevy Volt and I believe is still a problem for the Tesla roadster (which keep in mind ended up being a failure)

Yes the batteries generate heat, relative to the load, about 10%. That is not the primary reason for the cooling system. BEVs need cooling systems to extend cycle life by keeping the battery temperature as constant as possible despite fluctuations in environmental temperatures. The Tesla a high-end exotic toy, selling as a high-end exotic toy. Technically it performs largely as promised: ~200mi range, blazing speed off the line, hours to charge.

Is this why gasoline cars are so much cheaper than electric ones?

From an energy use stand point obviously the EV is cheaper than gasoline, even at today's price. Batteries aside, the EV overall is cheaper - no ICE, no transmission, no differential, no lube system, no gas tank, no large ICE radiator, etc, etc. But then this thread is about batteries vs FCs.

Not necessarily. An electric cars battery needs to be replaced and recycled several times (with current tech) during the cars life cycle.

Well current tech is Li-ion, so no; the Li batteries for the Volt should go 5000 cycles, 10 years, enabled by temperature stability and discharge limits.

As I am sure everyone knows, lithium chemistry based batteries aren't cheap to recycle and can do some serious damage if just disposed of in the environment

They're not cheap ($1k/kw-hr), so far. Lithium is not a heavy metal and is thus not a major environmental threat. The batteries need to be recycled just like the rest of the car.

Electric cars may be 0 emission in the long run but it comes with a big price tag. The #1 ingredient for fuel cells however is plain old carbon, and contains no toxic chemicals.

Last I looked the FCEV's being produced were costing Honda et al 6 to 7 figures a vehicle. FC's also have reliability problems (stack poisoning) over vehicle lifetimes and low temperature challenges (water exhaust -> ice).

And how would you know this? I refer you to an article I previously posted up above. Even a highly educated guess about economics at this point is still almost fantasy.

Hardly. DoE has done a lot of work on an H2 economy and found the problems extremely challenging. They've published studies costing out all the components - H2 production, storage, transportation, etc.
This link contains all of the DoE H2 2007 reports on the state of the art.
http://www.hydrogen.energy.gov/annual_progress07_storage.html#e

The Sanders slides in AutoGreen ... are based on an Ethanol infrastructure not Hydrogen per say, and certainly not H2 from electrolysis. So that's an entirely different conversation, viability of biofuels, etc. I tend to agree Ethanol->H2->FC is a plausible road ahead.

www.physorg.com/pdf85074285.pdf
http://spectrum.ieee.org/jan07/4848
http://www.batteryuniversity.com/parttwo-34.htm
http://www.rsc.org/chemistryworld/Issues/2007/October/HydrogenStorageTargetsOutOfReach.asp

 

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I think it is likely that the disadvantages of battery EVs will completely negate their efficiency advantage. Chemical batteries just aren't a very good energy storage, as they exist now.

Particularly, take the example of a Tesla Roadster, the failed $100k sports car. I think it's the only fair comparison, because it's the only EV with storage capacity (244 miles) comparable to a petroleum car. You could argue that is unfair, that a 40-mile range EV like the Chevy Volt is perfectly 'suitable' for ascetics who don't drive - but that defeats the point of this discussion, which is to highlight its disadvantages, not gloss over them.

First, there's the low energy density, even compared to hydrogen. In the Tesla, the batteries take up the entire back seat and half the trunk:

http://img104.imageshack.us/img104/3696/80882634vb004tesla.jpg

And even with that, it only seats two, and it needs heavy use of carbon composites to get the full (ordinary) mileage.

Wikipedia has a graphical comparison of energy densities - even on a volumetric measurement, liquid H2 is a full 10x more energetic than Li batteries. And only about 40% less than methanol, which (IIRC) is used in car racing.

Then, look at the charging time: 3 1/2 hours maximum, and that's at 70A @ 240V - far beyond the capability of a residential circuit (20A @ 120V I think?)

http://en.wikipedia.org/wiki/Tesla_Roadster#Battery_system

Even with a dedicated, high-power charging station, it takes a full afternoon to refuel. Replacing the whole battery pack doesn't seem sensible either, as it weighs 992 lbs. (You might as well replace the entire car - e.g., zip cars.)

It's not physically impossible, but for practice it seems far inferior to hydrogen power.

 

[signerror]

This H vs Batteries efficiency chart ought to be at the top of all threads like this, a sticky perhaps.

http://www.physorg.com/news85074285.html

Why does it say 'renewable electricity'? Is nuclear power not suitable?

I think it is a flaw to start with electricity at the top - heat sources like nuclear power (fossil fuel combustion, solar thermal, geothermal...) do not directly produce electricity. With thermochemical hydrogen cycles, water is split using heat as the only input - which replaces two steps, the (i) electricity generation (which your chart omits) and (ii) the DC electrolysis. I think this is a glaring omission. The chart depicts the intermediate conversion electricity -> hydrogen -> electricity, which is motivated by pragmatic issues (storage density). But it hides the conversion heat -> electricity -> hydrogen, where electricity is an unnecessary intermediate - and this is case is completely unnecessary.

Here's a talk from General Atomics.

http://gcep.stanford.edu/pdfs/hydrogen_workshop/Schultz.pdf

They estimate 50% direct efficiency (at 900° C - high-temperature helium-cooled nuclear reactors, or solar thermal plants), which completely alters the chart you brought up. Take a high-temperature thermal power plant, with two paths: a 50% efficient Brayton cycle, and a 50% efficient sulfur-iodine hydrogen plant. Then the end-point of "electroylsis" on your graph would be identified with the start point of "AC via grid transmission" - both start at 50%.

 

[mheslep]

I don't know what the bottom dollar price is but we pay about $1.95 per kg of H2 for our FC testing lab at school.

Then that is a subsidized price. As of a couple years ago, a standard cylinder containing 0.6kg H2 out of the phone book costs you $100/kg PLUS the cylinder rental.
Mass production, H2 economy costs:
http://www.nap.edu/openbook.php?record_id=10922&page=51

 

[mheslep]

...
Wikipedia has a graphical comparison of energy densities - even on a volumetric measurement, liquid H2 is a full 10x more energetic than Li batteries. And only about 40% less than methanol, which (IIRC) is used in car racing.

...]

See the other efficiency chart. H2 gives away its advantage in liquification, transportation, storage, and finally the fuel cell is much less efficient than the battery discharge - motor combination.

Then, look at the charging time: 3 1/2 hours maximum, and that's at 70A @ 240V - far beyond the capability of a residential circuit (20A @ 120V I think?)

http://en.wikipedia.org/wiki/Tesla_Roadster#Battery_system

Even with a dedicated, high-power charging station, it takes a full afternoon to refuel. Replacing the whole battery pack doesn't seem sensible either, as it weighs 992 lbs. (You might as well replace the entire car - e.g., zip cars.)

It's not physically impossible, but for practice it seems far inferior to hydrogen power.

Yes, recharge time is and will likely remain a major limitation for pure EVs for some time, hence the move to PHEVs such as the Volt. That 40 mi range covers a large chunk of daily US driving, and the Volt is a 4-5 seat vehicle.

 

[signerror]

See the other efficiency chart. H2 gives away its advantage in liquification, transportation, storage, and finally the fuel cell is much less efficient than the battery discharge - motor combination/

Even with 50% fuel cell loss, it remains five times denser (energy/volume) than Li batteries. That is not trivial.

Yes, recharge time is and will likely remain a major limitation for pure EVs for some time, hence the move to PHEVs such as the Volt. That 40 mi range covers a large chunk of daily US driving, and the Volt is a 4-5 seat vehicle.

Which is just a huge, intrinsic advantage of chemical-fuel vehicles like hydrogen, methanol, ethanol - and fossil fuels, petroleum, natural gas.

 

[Phrak]

It's meaningless to compare energy density without including the containment flask, which too me appears at least 5 times the volume of the contained hydrogen for small quantities in the 10-20 gallon range.

How much does a fuel cell cost capable of putting out 100 HP? Not tomorrow's price. Today's.

How much space and energy overhead does the particulate and dehumidifier cost?

Leakage of cryogenic fluids such as hydrogen can cause the accumulation oxidizers to dangerous levels. How?

 

[signerror]

It's meaningless to compare energy density without including the containment flask, which too me appears at least 5 times the volume of the contained hydrogen for small quantities in the 10-20 gallon range.

That's absurd. The LH2 tank I showed earlier stores 8 kg LH2 = 30 gallons; and visually its seems much closer to 30 gallons volume than 150 gallons. (I think of fish tanks as visual references). 150 gallons would be 20 cubic feet, which is 4ft * 3ft * 1'8", which would be the whole trunk. Or slightly bigger: looking it up, BMW 7-series have 18 cubic foot trunks.

http://auto.howstuffworks.com/auto-parts/towing/towing-capacity/vehicle/cargo-carrying-capacity4.htm

(Deep apologies for these units, they are not my choice. In metric: 8 kg hydrogen = 113 liters, and five times that would be half a cubic meter.)

http://www.wired.com/news/images/full/hydrogenbmw2_f.jpg

Another source says the BMW Hydrogen 7 LH2 tank is about 1 inch thick (2.5cm).

http://www.cars.com/go/features/aut...7hydrogen&make=BMW&model=Hydrogen+7+Prototype

How much does a fuel cell cost capable of putting out 100 HP? Not tomorrow's price. Today's.

Like Ivan in this thread, I think hydrogen combustion engines make much more sense. These are far cheaper than fuel cells. The BMW has 256 HP on hydrogen.

http://en.wikipedia.org/wiki/BMW_Hydrogen_7#Specifications

Leakage of cryogenic fluids such as hydrogen can cause the accumulation oxidizers to dangerous levels. How?

I understand these cars have external vents. You are referring to liquefaction of atmospheric oxygen on a cold surface, right? There is no such cold surface, nor any pools of leaking liquid hydrogen, so this should not be an issue.

 

[Phrak]

I'll stop kicking the sod, and get to the main issue. What's the price of a fuel cell? Without a answer to this, the rest is window dressing.

 

[Phrak]

Hydrogen produced on site, in the US means that nominally, 40 percent is from burning coal, with a site delivery efficiency of about 36%. But coal is bountiful and cheap. It costs only 100 bucks a ton. It's the reason we can sit a a desk and argue about hydrogen and wring our hands over global warming.

 

[signerror]

I'll stop kicking the sod, and get to the main issue. What's the price of a fuel cell? Without a answer to this, the rest is window dressing.

You're missing the discussion. I'm not advocating fuel cells. Neither is Ivan. We are advocating hydrogen combustion engines, taking a hit in efficiency in exchange for vastly reduced cost. The BMW I've been showing pictures of, it has a combustion engine. No fuel cells.

http://www.wired.com/news/images/full/hydrogenbmw4_f.jpg

"12-cylinder, 6.0-liter engine"

Hydrogen produced on site, in the US means that nominally, 40 percent is from burning coal, with a site delivery efficiency of about 36%. But coal is bountiful and cheap. It costs only 100 bucks a ton. It's the reason we can sit a a desk and argue about hydrogen and wring our hands over global warming.

I think the whole point of this thread is we're talking about replacements for petroleum-burning cars, exactly because of climate change. There is no point to EVs, or hydrogen cars, if their energy source is simply another carbon fuel. In my example, I am suggesting we use nuclear power to produce hydrogen, directly splitting water with heat (thermochemistry). Someone else suggested hydrogen from algae, and yet someone else solar thermolysis of water (far earlier in this thread).

 

[mheslep]

...Like Ivan in this thread, I think hydrogen combustion engines make much more sense. These are far cheaper than fuel cells. The BMW has 256 HP on hydrogen.

Agreed, for the near future, though H2 combustion with H2 infrastructure is still not cost effective when compared to a gas/electric plugin hybrid. H2 from ethanol might fly.

 

[mgb_phys]

The advantage of H2 for cars is that you can convert existing cars relatively easily (although not as easily as LPG).
The infrastructure costs depend on where the power is coming from, if you have solar power in Nevada and electric cars in LA then running power cables makes sense. If you have a solar plant in Saudi Arabia then shipping H2 is a lot easier than running a transmission line across the Atlantic.

H2 fuel cells are looking useful in marine applications where you are surrounded by water and space isn't a big problem.
Modern ships, especially cruise ships, use electrically driven pod motors with power generated from diesel and/or gas-turbine engines. There are restrictions on the stack emissions in harbour - fuel cells allow them to supply power for maneuvering and for onboard use without running the engines.

 

[mheslep]

...

How much does a fuel cell cost capable of putting out 100 HP? Not tomorrow's price. Today's...

The fuel cell need only provide average power - 20-30HP. Batteries/Capacitors can provide the peak power (and do in the demo FC vehicles).

 

[mheslep]

...

It's not physically impossible, but for practice it seems far inferior to hydrogen power.

<shrug> The reality is hybrid plugin electric - gasoline vehicles will go into medium scale production in the next few years from several mfns. H2 vehicles, either combustion or fuel cell, will not.

 

[mheslep]

I'll stop kicking the sod, and get to the main issue. What's the price of a fuel cell? Without a answer to this, the rest is window dressing.

...The committee observes that the federal government has been active in fuel cell research for roughly 40 years, while proton exchange membrane (PEM) fuel cells applied to hydrogen vehicle systems are a relatively recent development (as of the late 1980s). In spite of substantial R&D spending by the DOE and industry, costs are still a factor of 10 to 20 times too expensive, these fuel cells are short of required durability, and their energy efficiency is still too low for light-duty-vehicle applications. Accordingly, the challenges of developing PEM fuel cells for automotive applications are large, and the solutions to overcoming these challenges are uncertain.

The committee estimates that the fuel cell system, including on-board storage of hydrogen, will have to decrease in cost to less than $100 per kilowatt (kW)4 before fuel cell vehicles (FCVs) become a plausible commercial option, and that it will take at least a decade for this to happen.

http://www.nap.edu/openbook.php?record_id=10922&page=4
One to two years ago this was $1000 to $2000 per a PEM fuel cell kw, low qty. Solid oxide FCs offer a substantial reduction in cost.

Edit: In testimony before Congress, NREL used this study: http://www.nrel.gov/hydrogen/pdfs/39104.pdf" , which estimates ~$100/kw in 500k qty are possible, with platinum in the electrodes being the #1 cost driver. That compares to $30/kw for an ICE, noting that an ICE vehicle needs a lot more ancillaries.

 

[mgb_phys]

<shrug> The reality is hybrid plugin electric - gasoline vehicles will go into medium scale production in the next few years from several mfns.

Which is probably the worst of all worlds. With the possible exception of delivery vehicles and taxis operating in downtown where you care about pollution more than economy, hybrids don't make sense from a fuel economy/environmental/life time standpoint.
A 80mpg VW with a 1.2L diesel engine is better than a 35mpg Prius.

The reason for building hybrids is that you can stick a second battery and a slightly upgraded starter motor in your existing model and suddenly you are green.
Like the Ford F150 or the Merc S-class hybrid, 300hp gasoline engines with a 20hp 'hybrid' mode.

 

[mheslep]

Which is probably the worst of all worlds. With the possible exception of delivery vehicles and taxis operating in downtown where you care about pollution more than economy, hybrids don't make sense from a fuel economy/environmental/life time standpoint.
A 80mpg VW with a 1.2L diesel engine is better than a 35mpg Prius...

Pollution from a PHEV in EV mode (ie commuter) is zero at the vehicle.

That 80mpg VW is a small 50hp two seater. The Prius is a >100hp (ICE+electric motor) 4 seater/hatchback. Payback for non-plugin prices varies - some as low as a year, some never. The Prius is not a PHEV. PLUGIN hybrids can make a lot of sense, depending on the battery price and the cost of gasoline.

 

[mgb_phys]

What do you mean by a 'hybrid plugin electric'?

Gasoline hybrids are mostly a marketing invention to continue selling large cars as 'green'. Yes the VW is smaller - that's the point. But it's still a four seater 2 door hatchback, it's about the size of the original Golf(Rabbit).

Plugin electric vehicles will be great one day (hopefully soon) when people (on a certain continent) realize that they don't need a 2ton High Mobility Multipurpose Wheeled Vehicle to take a 5year old to school.

 

[mheslep]

What do you mean by a 'hybrid plugin electric'?

As I said - hybrid plugin electric - gasoline. http://en.wikipedia.org/wiki/Plug-in_hybrid

Gasoline hybrids are mostly a marketing invention to continue selling large cars as 'green'. Yes the VW is smaller - that's the point. But it's still a four seater 2 door hatchback, it's about the size of the original Golf(Rabbit).

Fine if you want small, just don't compare to it substantially more powerful and larger vehicle when citing mpg.