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The Arguments for Hydrogen Combustion Engines
26 September 2006
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| BMW envisions the development of hydrogen combustion engines that eventually use charged, direct injection to deliver high efficiency. The current Hydrogen 7 is represented by the H2-PFI column. Click to enlarge. Source: BMW |
Speaking at the California Air Resources Board Zero Emissions Vehicle (ZEV) Symposium, representatives from Sandia National Laboratories and BMW laid out the rationale and technical strategies for a focus on hydrogen-fueled combustion engines (H2ICE).
Using hydrogen with a combustion engine, according to Dr. Andy Lutz from Sandia, is a pragmatic bridge to a hydrogen economy. The technology is available today and economically viable in the short term, with fewer constraints concerning hydrogen storage compared to fuel cells. Impurities, for example, are a non-issue for a combustion engine (“You burn them right up.”).
PHydrogen engines have demonstrated efficiencies (BTE) in excess of today’s gasoline engines, NOx is the only regulated tailpipe pollutant resulting from hydrogen combustion, and carbon dioxide is a non-issue, at least in terms of the driving (Tank-to-Wheels) component of the lifecycle.
Although current efforts by Ford and BMW reflect early stage development, both BMW and Sandia outlined technology approaches for subsequent generations of H2ICE systems that could deliver significant improvements in fuel economy and emissions reduction, while delivering additional power.
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| BMW’s projected product pathway. Click to enlarge. Source: BMW. |
Dr. Edgar Berger from BMW, in particular, described a future generation H2ICE 4-cylinder engine that could deliver more than 140 kW (188 hp) of power with fuel consumption of 1.4 to 1.6 kg H2/100 km.
One can reach, in fact, 1kg/100km H2—but the price is to reduce vehicle properties and customer benefits.
—Edgar Berger
In terms of its basic combustion properties, hydrogen offers certain benefits and certain challenges compared to gasoline. (See table below.)
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| Combustion properties of gasoline, CNG and hydrogen. Favorable hydrogen properties are tagged in blue; unfavorable in red. Click to enlarge. Source: Sandia National Laboratories |
Its wide flammability range (Φ) supports a much leaner burn mixture—a factor that is important for emissions management strategies. The much higher laminar flame velocity produces stable flames under more extenuating circumstances, and, combined with the higher autoignition temperature, creates a higher research octane number that supports higher compression.
On the downside, hydrogen has a high stoichiometric volume fraction, which affects how much charge passes through the engine in a given displacement, and in turn affects the power of the engine.
It also has a lower minimum ignition energy and hence has a tendency to pre-ignite.
The researchers at Sandia have identified five possible approaches to dealing with the challenges posed by hydrogen combustion.
Continuous ultra-lean (Φ<0.45) operation with improved power densities. This, combined with turbo- or supercharging is the approach Ford is taking with its H2ICE Focus passenger car and E450 shuttle bus. For also has a H2ICE-hybrid research vehicle—the H2RV— that combines a 2.3-liter combustion engine with a 30 hp electric motor. All vehicles deliver SULEV emissions or better.
Operate at stoichiometric conditions (Φ=1) with aftertreatment. Possible routes within this strategy include the use of liquid fueling to prevent preignition if the fuel can be kept cold to the point of injection; direct injection, and the use of Exhaust Gas recirculation.
A multi-mode strategy. This is the approach BMW is taking with its Hydrogen 7, running ultra-lean under partial load to minimize engine-out NOx, and at stoichiometric condition under full load, coupled with the use of a three-way catalyst to handle the resulting NOx. (Earlier post.)
Another variation of the multi-mode strategy uses ultra-lean mixes at low load, pressure boost in the medium range, and then lean NOx traps at high load. Ford is looking into this for the H2ICE Focus.
Mixture stratification with direct injection. This approach would use a stratified and extremely lean mix at idle. At low-load, it would move to an ultra-lean homogeneous mixture. As load increases, the system would start using stratification with direct injection, and then rely on the lean NOx trap at high load. Sandia concludes that such an approach could theoretically deliver BTE of greater than 45%, with emissions significantly below SULEV.
Click to enlarge. Source: Sandia National Laboratories
It’s complicated, but with electronic controls there are a variety of things that can be done.
—Andy Lutz
For its part, BMW outlined an ambitious development plan that it intends to result in mono-fuel hydrogen engines with greatly improved efficiency and reduced fuel consumption that it can apply across its entire model range, from luxury to compact.
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| Advanced energy management. Click to enlarge. Source: BMW. |
Mirroring some of the Sandia work, BMW is ultimately looking toward a charged, direct-injection engine as a future generation platform. Berger also described a hybrid architecture that would combine a small fuel cell with the hydrogen combustion engine to augment electric power for vehicle subsystems and traction power.
A key enabler for this strategy is having sufficient hydrogen on-board to fuel the engine. BMW has already opted for liquid hydrogen storage, with its higher volumetric and gravimetric densities than offered by compressed hydrogen.
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| Volume and weight of different methods of storing 10 kg of hydrogen, which is equivalent in energy to 38 liters of gasoline. Click to enlarge. Source: BMW. |
However, BMW believes that it needs to have 10kg on board hydrogen to met its performance and customer satisfaction objectives. Currently, the Hydrogen 7 stores 8 kg in a 150-liter container.
Accordingly, BMW has work underway to expand the storage density of its liquid hydrogen storage, to decrease the boil-off loss, and to increase the loss-free dormancy time.
Furthermore, for its 5 Series size cars, BMW is developing a shaped storage tank it calls the “double bubble”—a single-tank system providing central storage running down the midline of the car in the tunnel.
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| BMW’s hydrogen storage roadmap. Click to enlarge. Source: BMW. |
Ultimately, it sees using liquid hydrogen in the larger classes (luxury and executive) with 7.5 to 10 kg in a given total package of 250-300 liters. For small to medium-class vehicles, BMW is looking at compressed hydrogen, and possibly some activity with cryo-compressed hydrogen.
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September 26, 2006 in Engines, Hydrogen | Permalink | Comments (52) | TrackBack (0)
Comments
Posted by: Gagar | October 13, 2006 at 06:25 PM
Mr. please,
Your math is quite impeccable, however, calculation does not always accurately predict real life. Actual testing by the manufacturer is more accurate. Look at the most recent GCC article on the Mitsubishi MiEV car: http://www.greencarcongress.com/2006/10/mitsubishi_acce.html
and you'll find that the car can go ~100 miles on a 20kwh battery. This means roughly 200wh/mi, dividing 20,000wh by 100 mi, for a mini-mouse car that is definitely sub-sub-compact, weighing perhaps ~2000 lbs, vs the Prius II classified as a compact car larger than the Corolla or the Civic, weighing almost 3000 lbs. So, 240wh/mi for the Prius is not unreasonable.
That would put the 214wh/mi for the S-10 pickup truck in question. Toyota RAV4-Ev has a 27.4 kwh battery pack for a range of 80-120 mi. Assuming a middle number of 100-mi-range for steady cruise at ~48mph (while cruising at 30mph and 60mph will give you ranges of 120 and 80 miles, respectively), and dividing 27,400wh / 100 mi will give you 274 wh/mi. And we know that the RAV4-EV is a lot smaller than the Chevy S-10 pickup truck, don't we?
Posted by: Roger Pham | October 15, 2006 at 05:13 PM
It is interesting that the chart shown comparing gasoline, compressed Natural gas (CNG) and hydrogen for ICE engines indicates that in almost all aspect CNG is superior to H2! And since the cheapest source of H2 is natural gas, and natural gas has approx. 3x the volumetric energy density of H2 (less storage space needed), then it makes absolutely no sense at all to burn H2 in a ICE engine - burn CNG instead. Also, instead of liquid H2 that requires chilling to −252.87 °C, Natural Gas liquifies at a more reasonable −161.6°C
I don't think BMW is serious in using liquid H2 for cars - they just want to get some "green" attention away from their rivals.
Posted by: Chris Muir | October 15, 2006 at 08:05 PM
On the second thought, Mr. Please, you're bringing up a good point re 1600-1700 rpm at 48mph, which is not optimal for maximum efficiency.
You stated that this is done to reduce the lag time required to rev up the engine for quick acceleration. While this may be true in a non-hybrid with CVT like the Nissan Altima, in which the hwy mpg is not better than the 5-speed Toyota Camry automatic.
But in a full hybrid, let's not forget that the 21kw battery is standing by to provide the necessary juice to assist the engine in reving up. Your engine can barely be humming along at 1300 rpm at 48mph, and when you floor the gas pedal, the current from the battery worthy of nearly 30 hp (almost 1/2 of the engine rated max power output) will be sent to the traction motor to assist in acceleration, while torque load is transiently eased up on the engine allowing it to quickly rev up. If this approach is done, there is no doubt that the Prius will be able to cruise on maximum engine BTE, and the TTW efficiency can reach the claimed 37%. This may be the basis for Toyota's claim that the Prius is capable of 37% TTW.
But in real life, the Prius cruises at higher engine rpm at the expense of maximum efficiency! You have proof of that! Why did Toyota chose to do so? The answer may have to do with the EPA requirement that the battery warranty must extend to 8 yrs or 100,000 miles. You see, frequent use of the battery will shorten its life, and that means big forthcoming warranty bills for Toyota. So, until more durable battery technology come along, or UltraCap technology allowing infinite charge-discharging cycles, Toyota has chosen to hold back on battery boost as much as possible. Therefore, to maintain "driveability" in the abscence of battery boost, the engine rpm must be raised.
So, you may be right! The current Prius at 51 mpg hwy cruise may represents less than 37% tank-to-wheel efficiency. The 37% number TTW may represent Toyota's forward-projection statement to the near future when battery will be much more durable, allowing battery boost ad nauseum, for the sake of comparison of technologies between HEV and FCV as the intended subject in Toyota's website.
Good work, Mr. Please. I'm so proud that GCC forum has such caliber of intelligent, well-informed and determined participant.
Posted by: Roger Pham | October 15, 2006 at 09:13 PM
Chris Muir,
Good observation. I've made similar point regarding H2-ICE-HEV capable of burning methane as well, as a cheap and easy way to boost range 3 folds without resorting to inefficient LH2 or high pressure of 700 bars.
The rationale for H2 lies in its versatility, being the easiest fuel to produce from any kind of combustible materials such as coal, crude oil, waste biomass, AS WELL AS to produce H2 from renewable energy such as surplus wind electricity, or solar energy (Zinc or Boron reacting with H2O to produce H2 and using solar heat to reclaim the Zinc or boron oxide) or solid oxide high temp electrolysis, high-temp nuclear reactor, etc...
For local commute, the 120-150-mile range of a H2-car is no problem, with fill up in minutes while u grab a donut and some Am coffee from 7-11. U will be rewarded with clean air with the pride of contributing to the future of clean and sustainable mobility.
With Crisis comes Opportunity. Strength can only be honed from Adversity. No Pain, No Gain! The bulkiness of H2 is the best way to force car Mfg's to maximize fuel efficiency. No CAFE regulation can do it, no politician will risk their re-electability to raise the gasoline tax. Necessity is the Mother of Invention. There is no way that you can convince GM to make an SUV capable of the equivalence of 50mpg. But, thanks to the bulkiness of Hydrogen, the new GM Sequel FCV is capable of 50 mi/kg of H2, and GM is doing it out of their own freewill. What a Miracle, indeed!
Posted by: Roger Pham | October 15, 2006 at 09:41 PM
Mr. Pham, you're making me blush! :p In terms of why the Prius won't see maximal TTW, you are definitely right, the additional load on the batteries is almost certainly why they couldn't use the electric motor, especially because it would need to pull plenty of current from the pack. Which, if these NiMH's are anything like the 10ah NiMH's we can pick up from the store, will really kill the battery life. Usually something like 1000 cycles to 80% DOD at .1C rates, 500 cycles to 80% DOD at .2C rates, and 400 cycles to 80% DOD at .25C rates, so having any rate that approaches 3C will hurt in the long run. In any event, it explains why there's such a huge increase in the supposed mpg rating of the next gen li-ion powered Prius.
When comapring vehicles, especially EVs, we really need average speed to compare wh/mile ratings. Generally EVs, especially those sold in the CA market, will have the range/electricity consumption assuming an average speed of ~65mph highway since, unlike a gasoline vehicle, where engine efficiency increases as veicle speed/efficiency decreases, EVs will show the driver exactly how aerodynamic drag increases as a square of the speed.
I suppose they could use the average speed assumed by the EPA of 48.3mph, but because vehicles in CA do not ever drive that slow, there would be quite a few stranded EV owners... Going from 45mph to 60mph increases the S-10 EV's energy consumption by over 30% or ~100wh/mile and cuts over 20 miles off the range. I'm guessing the range of the RAV-4 EV and i MiEV both reflect what the real world range would be, instead of basing it on the EPA electric mpg equivalent. Actually, they definitely base it off of something besides the EPA equivalent electric mpg rating, because that is all kinds of crazy. Check out note no. 12 in this pdf...
http://www.teslamotors.com/display_data.php?data_name=21stCentElectricCar&js_enabled=1
Posted by: yesplease | October 16, 2006 at 02:48 PM
edit- for the S-10 EV, compared to the base levels, a ~30% increase in speed results in a ~50% increase in consumption of electricity.
Posted by: yesplease | October 17, 2006 at 04:38 AM
The tecnology that needs to be developed is a devise that would get the hidrogen from destilated water seconds before its use. That way there is no need to storage and logistic of distribution of hidrogen. With 12v and 500mA on carbono electrodes you can get 14ml of hidrogen every 10 minutes. Do the math and ther is a way.
This is the only way to success on this proyect. Any other is just marketting and loss of time.
Posted by: Steve | October 19, 2006 at 08:13 PM
Speaking as an average Joe with far fewer brain cells than the average here, how on earth are the costly and complex vehicles advocated here better than a cheap, simple, currently available small diesel engined car such as a Citroen C1 which is easily capable of around 70mpg?
Posted by: Nick Street | October 29, 2006 at 01:46 PM
Nick,
The first take-home message here is that hydrogen-burning engines (H2-ICE) aren't neither costly nor complex. H2-ICE in fact, should be simpler than diesel engine due to the absence of complex emission control equipment, except for the lean NOx trap for use mainly at high load. The lower compression H2-ICE should be lighter and cheaper to make than diesel. The fuel in H2-ICE is already under high pressure, therefore an expensive ultra-high pressure pump in common rail diesel injection is not needed.
The second take-home message is that hybrid Electric drive necessary for high efficiency is no more complex than a 4-speed automatic transmission. In time, hybrid electric vehicles will not cost any more than a regular vehicle.
The third take-home message here is that as far renewable fuels go, H2 is far easier and more efficient to produce than synthetic diesel fuel from F-T synthesis, hence will be a lot cheaper in the future when petroleum will run scarce. Don't let anybody misinform you any otherwise.
Posted by: Roger Pham | October 31, 2006 at 02:38 PM
Grammatic correction on double negatives: The first sentence on my previous posting should read: "H2-combustion engine are neither costly nor complex."
I can imagine my English teacher shaking her head!
Posted by: Roger Pham | October 31, 2006 at 02:42 PM
@yesplease
I conclude with Roger that your calculations are impeccable. Too impeccable to be precise. The drag at 48 mph you calculate is under ideal circumstances: 20° C, no wind, level road, absolute constant speed. But the consumption you put against that theoretical situation is more real-world data. I can assume that the EPA test includes a cold start, accelerations, higher speeds than 48 mph, etc.
To make your calculation correct, you must not take the EPA highway consumption, but the momentary consumption when the Prius is doing 48 mph. I believe the fuel consumption at 48mph or 77 km/h under ideal circumstances (no wind, 20°C, low humidity, level road) is more in the region of 3.5 l/100 km or 68 mpg. Which is 30% better than the 51 mpg you used in your calculation.
Hope to see your reaction.
Posted by: anne | November 06, 2006 at 08:35 AM
re: relative weights of RAV4 and S-10
I think the Chevy could be lighter... some are sub-3000 lbs. See http://autos.msn.com/research/vip/spec_Exterior.aspx?year=1991&make=Chevrolet&model=S10%20Pickup&trimid=-1 vs. http://www.edmunds.com/new/2007/toyota/rav4/100777076/specs.html
cheers,
Bill
Posted by: Bill | November 06, 2006 at 01:13 PM
Just stumbled upon this site. Everyone, check out Denny Klein's site : www.hytechapps.com He has the answer to hydrogen technology for internal combustion engines! His invention produces hydrogen on demand by using his power plant in the trunk and using very few modifications to oem equipment. He puts a larger alternator on his hybrid autos and injects the hydrogen with the fuel and he doubles his mileage while burning the fossil fuel so completely that there is virtually no emissions! Why not produce hydrogen on demand at a very low psi instead of sitting on top of a bomb using hydrogen cells? He has made 2 hybrids and can go 100 miles on 4oz. of water. He says it's ready to go today, not 10 years down the road. He also says it can be retrofitted to any vehicle on the road today. He can apply this technology to any fossil fuel burning power plant, whether it's a gas furnace or an electric power plant burning natural gas to make electricity... I tell you, HE HAS THE ANSWER!
Take a look at his website!
Later,
Greg
Posted by: Greg | November 09, 2006 at 07:30 PM
Lexus is now marketing a car that parks itself, (for the parallel parking challenged). It uses computer-controlled steering and video coordinates. Question: What are the two words you never want to use while driving down the freeway in this car?
Answer: PARK CAR. A soft-spoken computer voice will answer: "Daaave. Are you sure you want to park the car now, Dave? We seem to be moving awfully fast for parking right now? Are you sure? Now? Dave? Daaave? I can't hear you, Dave. You paid a lot of money for this car and you know parking right now will cause a horrible wreck, Dave. Daaave?
Ha ha.
Posted by: Wells | November 14, 2006 at 03:55 PM
Lol, that sounds like some horror movie from H.G. Wells
The website on the previous post looks promising, althought it is not really a H2-ICE.
but it does look like a good catalyst to increase efficiency of ICE engines (or convert electric power to something u can burn)
Will it fit a bike?
Anyway, I don't think this hydrogen economy can work because you just don't 'dig' for hydrogen
Posted by: Ramizan | November 14, 2006 at 08:20 PM
You have to think outside the box. Yes, there will be resistance in accepting hydrogen fuel because it cannot be dug up but I am anxiously waiting the new era. Whether it is totally hydrogen or a fossil fuel hydrogen mix, I encourage every inventor, back-yard mechanic, or scientist to strive for an abundant, clean burning fuel of the future. The future is now!
Ray
Posted by: Ray | November 19, 2006 at 07:12 PM
These are all good arguments for and against. The long view is that we have to try things to move forward and H2 appears to be the long term for now. Hydrogen is a good fuel that is long term and we need to learn how to efficiently extract it from H2O. In the meanwhile other ways may provide a transition. We learn from mistakes and wrong turns. What we need is an engine that runs all fuels, so that any local production of any type of fuel will be quickly usable. How about a Universal Fuel Engine that runs any fuel to unite H2 and CNG or Ethanol, Methanol, BioDiesel, Propane, FastFoodGrease, etc, sources? See previous GreenCarCongress article http://www.greencarcongress.com/2005/10/concept_a_unive.html#more
Posted by: walt | November 29, 2006 at 08:21 AM
THE ONLY WAY TO GO!
The French "MIDI" "Air-Car", and the Korean "PHEV" "Air-Electric-Car" are out in front with the most advanced developments of POLUTION-FREE Cars! And, new improved- capacity tanks, plus improvements in battery design, and a new AIR ENGINE developed in Australia, should make these 'Air Cars' the preferred cars of the future! No need for carbon monoxide fumes, or paying GREEDY BIG OIL 'ransom'? for Natural Gas?, or Hydrogen?
Air tank refillS are almost 'instant'!
And batteries are recharged while coasting, or
driving-on-air-power; or at 110 or 240 volts!
'Only way to go'!
Jim Hanley
Posted by: Jim Hanley | November 29, 2006 at 03:40 PM
What it boils down to is BMW wants to take the shortcut method on producing hydrogen power trains. The system GM has in place so far is years ahead Of BMW, probably because GM started on their research over 10 years ago.
Posted by: jttison | December 01, 2006 at 10:02 AM
I can assume that the EPA test includes a cold start, accelerations, higher speeds than 48 mph, etc.
The EPA highway test involves a warm start, accelerations (Every test involves accelerations, so, sure?), a maximum speed of 60mph with an average of 48mph, and Free-flow traffic at highway speeds, so I'm guessing one braking event at the end. The reason I took the EPA highway figure is because it is controlled and consistent, unlike any anecdotal/personal accounts.
Posted by: yesplease | December 15, 2006 at 09:51 AM
What a joke, hydrogen ICE? Too many losses in generating the hydrogen, storage, transportation already and now someone thinks that hydrogen ICE is the way to go.
I might as well charge an electric car equipped with Li Ion or Lipo battery. Well-to-wheel cost and CO2 benefit can easily wipe out any future of hydrogen ICE.
Can we rid ourselves from the nonsense of hydrogen economy and start focusing on what actually good for the planet and environment.
Posted by: Azmio | January 03, 2007 at 01:44 AM
The onboard generation of hydrogen from water, supplying H2 seconds before we need it... is it for real? In the first place, where will the energy comes from to liberate hydrogen and oxygen from water.
Next, when we apply the thermodynamics law, will we get 2 Btu if we invest 1 Btu of electricity? Come one guys, let's go back to basic and let's use well-to-wheel efficiency as our guiding principle.
Posted by: Azmio | January 03, 2007 at 02:01 AM
The onboard generation of hydrogen from water, supplying H2 seconds before we need it... is it for real? In the first place, where will the energy comes from to liberate hydrogen and oxygen from water.
Next, when we apply the thermodynamics law, will we get 2 Btu if we invest 1 Btu of electricity? Come one guys, let's go back to basic and let's use well-to-wheel efficiency as our guiding principle.
Posted by: Azmio | January 03, 2007 at 02:01 AM
I don't know all of the science to this. All I know is that I have three friends here in Colorado that have the Toyota Hybrids and guess what dudes, on the highway they get no where near what your "calculations" show.
More like 45 mpg max... most get about 39-42 on the highway.
Real life is quite a bit different than Government controlled or manufacturer controlled testing.
I've been with my friends and they all use cruise control and they are NOT going WOT all of the time...
I'm all for Hydrogen run cars. Your storage issues will be solved. Fuel cells will not catch the immagination of the public. Why? Because man still loves fire, boom booms too much. There is a HUGE market and millions of jobs in the Aftermarket for autos. Fuel Cells do not suupport the aftermarket, nor can it.
There is no man-made global warming so all of those CO2 emissions concerns are bogus..dudes.....look at the history and the facts and quit b.s.ing yourselves and others over some "feel" good "save the earth" crapola...
Let's get on with it. You can manufacture Hydrogen running production plants in tandem with current steam run power grid sources. The steam used to run the generators for regualar electriccal needs for the grid could also be used to produce the electricity for the electrolysis before it hits the cooling tanks...
With Nuclear energy it's even sweeter...
We can debate how many angels can dance on the head of a pin, and get our panties all in a bunch if we wish, but the fact still remains, technology today can support Hydrogen internal combustion engine driven vehicles including Jets airplanes. Let's stop debating and get on with it!!!!! :)
May god bless,
Father O'Malley
Posted by: Father OMalley | July 30, 2007 at 12:38 PM
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Plus, nothing about platinum which is used as a catalyser in the cell. It's said that if all platinum extracted fron South Africa (which account for 70% of the world production) would go for hydrogen engines, it would be enough for as much as 5 millions cars/year....... .............. no for everybody though....
So, I am wondering what is their (BMW and all others) point ? Sell their technology maybe ?? ;-)