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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.
Resources:
Technical Review of Hydrogen-fueled Internal Combustion Engines (Sandia)
BMW H2 NZEV Development (BMW)
September 26, 2006 in Engines, Hydrogen | Permalink | Comments (52) | TrackBack (0)
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> Using hydrogen with a combustion engine, according to Dr. Andy Lutz from Sandia, is a pragmatic bridge to a hydrogen economy.
Yeah - a bridge to nowhere.
Posted by: eric | Sep 26, 2006 5:56:27 PM
BMW's system could be an excellent starting point for short-hop passenger and cargo aviation applications. For vehicles, LH2 makes no economic and little if any ecological sense.
Posted by: Rafael Seidl | Sep 26, 2006 9:16:00 PM
All that talk about engines, and nothing about the big issue: how to get the hydrogen.
Posted by: Engineer-Poet | Sep 26, 2006 9:20:46 PM
What if you want to leave your car for a month? Do you have to vent the liquid hydrogen tank? There is no way to eliminate boil off of LH2. Finally it takes something like 40% of the available energy to liquify hydrogen which is much worse than the 20% or so needed to compress it to 10000psi.
Posted by: Ender | Sep 26, 2006 10:04:46 PM
The recently announced hydrogen BMW 7 series loses (boils off) its fuel in 9 days! Lose one-ninth of your fuel every day; what a deal!! Not ready for prime time.
Posted by: pauln | Sep 26, 2006 10:48:30 PM
If you're burning the fuel in an IC engine, you might as well stick with hydrocarbon fuels and balance emissions by extracting CO2 from the air or ocean surface waters. The fuel tank would be much smaller (even if you use CNG).
Posted by: Paul Dietz | Sep 27, 2006 6:30:10 AM
The planet cannot afford to burn extra gas and coal in power stations to make hydrogen to burn in engines. CO2 on a well to wheel basis is awful.......just about the worst fuel possible.
BMW should burn CNG in their cars, the filling stations exist in Germany, no range issue, can even use bio-methane from landfill to run BMWs...truly sustaianable performance. This is inevitiable.
Posted by: John Baldwin | Sep 27, 2006 11:05:25 AM
With an H2 ICE, you need just about as much energy as you would for a gasoline ICE as the efficiency of the H2 ICE is not much better. With a H2 FCV, tank-to-wheels efficiency improves, and you need less onboard storage. This is yet another reason why H2 ICEs are not going to be a very practical bet (despite what BMW says), the main reason being that the well-to-wheels efficiency and emissions are horrible.
Energy storage density is obviously a problem with PHEVs and EVs too, (it would be cool to see a similar graphic for that), but you get 3-5x the tank-to-wheels efficiency, so you need 1/3-1/5 the on-board energy storage, which is not the case with H2 ICEs and even FCVs aren't anywhere near as close (a little more than 2x the efficiency if I remember correctly). Plus you get boil-off if you are using LH2 so you lose fuel if your car sits parked for a while (which I can't imagine consumers would like).
PHEVs are a much better short-term bridge to an electrified vehicle fleet. H2 ICEs are a bridge to more or less nowhere.
Posted by: JesseJenkins | Sep 27, 2006 12:47:10 PM
Ah, the argument for H2-ICE is very strong. As I've suspected, the efficiency for H2-ICE can approach 45% using the mixture stratification with direct injection. Of course, all ICE's are most efficient at only at a narrow range between 50%-70% of maximum throttle, meaning that an ICE-electric hybrid will be needed to keep the engine running only in its most efficient range of 45% BTE for most of the time. The gasoline Prius is already calculated by Toyota to have a tank to wheel efficiency of 37%, so 45% efficiency for H2-ICE-electric hybrid is a realistic expectation. In comparison to the Honda's upcoming fuelcell FCX with announced 60% efficiency, this is not so bad, given the lower cost and the higher durability of H2-ICE's in comparison to PEM fuelcells.
To all H2 doubters,
The first thing to remember is that H2 can be produced very easily and very efficiently from almost any type of combustible feedstocks. Meaning that a gasoline station in remote areas can be supplied with crude oil, or natural gas, waste biomass etc. and can produce H2 on the spot. A car running on H2 can vicarously use any type of combustible fuels, and not dependent ONLY on one type, such as gasoline car on gasoline with appropriate octane rating with added ethanol or other kind of additives, or diesel depended on low sulfur fuel with appropriate cetane rating. Gas stations in large cities can have H2 piped-in from a local central H2 reforming plant, with optional CO2 sequestration means.
Given the inefficiency and great expense of H2 production from electrolysis of water at room temp, do not expect this to be the source of H2 for mass consumption. There are other methods of H2 production from renewable energy that can rival the BEV or PHEV in term of total source-to-wheel efficiency. Please look at this link http://www.greencarcongress.com/2006/09/quantums_compre.html
for my last posting that discuss highly-efficient way to generate H2 that can rival the BEV in term of total efficiency.
Rafael,
I think that BMW plans to use compressed H2 for smaller or lower-cost automobiles.
But, for the high-end autos with heavy weights due to over-abundance of luxurious items, compressed H2 do not offer sufficient volumetric efficiency as LH2 for sufficient range, ergo the use of LH2. The efficiency of LH2 sucks in comparison to compressed H2, but the rich surely can afford it. Those who are wealthy enough to purchase BMW's costing over 100,000 USD do not have to worry about fuel efficiency, only about how far between fill-up, as their time is worth a lot of money. (eg. lawyers at >$150 hourly fee)
LH2 is excellent for commercial aviation jets, and the value of LH2 is not just limited to short hops. The longer the range, the more energy-saving when using LH2. Those who wonders why this is so can look for my previous posting on the same subject.
Posted by: Roger Pham | Sep 27, 2006 10:32:51 PM
...continues from above,
This article left out the most important advantage of H2-ICE-electric hybrid over that of FCV: the ability to combust methane-H2 mixture at any ratio. Methane allows over 3 times the volumetric energy density of H2. Thus, the compressed H2 tank needs not be overly large, but just sufficient for a range of ~120-150 miles. If a range of 360-450 miles is desired, just fill up the tank with a mixture of up to 90% methane and 10% H2 (to improve ignitability), and this is a much more cost-effective solution over that of LH2. Of course, in the future, H2 is expected to be produced cheaper and more energy-efficient than methane from renewable energy sources, so most people will probably choose H2 for daily commute. A fill up every 4-5 days with H2 for daily commute is probably Okay, as it will give one time to grab a cup of coffee, a donut or time to glance at the newstand at a local friendly 7-11 gas station. Those high-dollar doctors or lawyers probably will choose to fill-up with methane instead, and pay a price premium. But, hey, this a free capitalistic country. Different strokes for different folks! Those BEV enthusiasts may choose to miss out on the brief weekly social gatherings at 7-11 gas stations altogether and plug in their vehicles at home instead.
Posted by: Roger Pham | Sep 27, 2006 10:54:49 PM
H2 can only be made efficiently from chemical fuels (mostly hydrocarbons, alcohols and the like). Electricity can be made from all of the above, and much more. Further, the efficiency of gasification to H2 is around 80%, yielding 36% best-case throughput in a 45%-efficient engine; current batteries can hit 90+% efficiency. Even if you burn natural gas in a CC turbine to make juice (60%), you can get 54% throughput - 50% better than hydrogen.
Energy security is the other side of the coin. The fewer the options for the energy supply, the less secure you are. Hydrogen is inherently less secure than electricity.
Posted by: Engineer-Poet | Sep 28, 2006 6:37:35 AM
Eng-Poet,
You're getting very close. CC Turbine has an efficiency of 60%, however, transmission to the home socket is only 90% efficient, leaving 54% efficiency from power plant to home socket. BEV is generally accepted as having a grid to wheel efficiency of ~70%, considering all the losses in the charger, battery, power inverter, resistance in the motor, friction in the drive train, etc...So, multiplying 54% by 70% will leave you with 37.8% total efficiency for BEV, which is not too far from a calculated number of 36% overall efficiency for an optimized H2-ICE-electric hybrid vehicle. Now, if your electricity comes from coal in conventional coal power plants having ~40% efficiency, as in 50% of electricity production in the USA, and multiply by 90% efficiency from power plant to home socket, and multiply by 70% efficiency of BEV, you'll have only 25% efficiency for BEV from coal to electricity. Whereas, if you gasify this coal and produce H2, you'll have higher efficiency for H2-car.
Posted by: Roger Pham | Sep 28, 2006 8:29:03 AM
Your hydrogen car efficiencies don't include drivetrain losses, so you should omit them from the EV example too. You also assume that the H2-combustion car will always be running at its best efficiency - it can't, while the EV mostly will.
Posted by: Engineer-Poet | Sep 28, 2006 5:04:36 PM
Eng-Poet,
The Prius has a tank to wheel efficiency of 37% as posted by Toyota's site. This includes all drive train losses. Due to the higher efficiency of H2 combustion, including higher compression ratio, isochoric combustion process, and ultra-lean burn regime (thanks to high ignitability of H2 at very low concentration) in which less heat rejection into coolant and more heat available to do work, an increase from 37% tank to wheel to 45% tank-to-wheel would be achievable. A full hybrid drive train would ensure that the engine is used only in the most efficient power range. EV's don't run at its highest efficiency in hard acceleration, either, due to higher resistive losses in all circuitries including motor windings, power inverter and batteries. If you race R/C electric cars or fly R/C electric planes, you would realize this. The higher the power setting, more electrical energy will be wasted to heat production.
Posted by: Roger Pham | Sep 28, 2006 5:34:27 PM
All those advantages are reversed if you don't start with a fossil fuel. That's my complaint about hydrogen: it looks like a scheme to lock in the interests of the fossil-fuel corporations for the next century, and the hell with the environment.
Posted by: Engineer-Poet | Sep 29, 2006 9:05:34 PM
Engineer-Poet is certainly on the proper side of the equation. We all know that it is much easier (and much cleaner) to make, transport and use electricity (in road vehicles) than Hydrogen.
Our electricity is 98%+ from Hydro and will be a combination of wind + Hydro for decades to come. We could supply enough clean electrical energy for most PHEVs and EVs in eastern USA for an extended period.
Our support and efforts should go for the development of on-board high efficiency Energy Storage Devices required for PHEVs + improved PHEVs + EVs and the progressive elimination of noisy polluting ICE vehicles.
Of course, more clean electrical energy should be produced from Hydro-Wind-Sun-Waves (and improved nulear)to meet the new demand created by a few (many) million PHEVs and EVs. It can be done. Most industrial countries have the required potential ounce the demand is created.
Posted by: Harvey D. | Oct 1, 2006 8:29:28 AM
Roger Pham,
From what I've gathered the 37% is maximal engine bte efficiency, and is generally not the efficiency the engine is usually operating at, which is more like 20-25% EPA highway, and 25-30% assuming the usual 70mph regime most Americans use. Peak efficiency is not average efficiency, which is what should really be assessed, and why in the ICE realm, diesels tend to get twice the mileage (btu corrected) that gassers do.
High BTE (>40%) over a significant portion of the rpm/pressure map has been shown with SI PFI methanol fueled engines, so why bother with a fuel that's so much of a pain to produce/store when we have engines right now that can exhibit these high thermal efficiencies?
Posted by: yesplease | Oct 2, 2006 2:25:04 PM
Please, Mr. Please...(don't play me 17...) if u r old enuff to remember the song!
A typical modern gasoline car is accepted as having a overall BTE of 20% combined driving tank to wheel. (older cars with carburetor were accepted as having BTE of 15% combined driving). A gasoline car the size of the Prius should have a combined fuel efficiency of ~30mpg EPA. The Prius has a combined EPA mpg of 55mpg. Take 20% divide by 30 and multiply by 55 will get ya 37%. The 37% for the Prius reflects combined driving, NOT peak engine efficiency. A full hybrid drive train is designed to let the engine run as much at its peak efficiency as possible. For that reason, full hybrids engines don't idle, and don't run at low car speed, either. The electric motor does all the low-speed traveling. It only comes on strong at near its peak BTE to recharge the battery, or to pull the car at cruise. The engine is turned off during coasting also. The engine is down-sized significantly so that at cruise, it runs close to its peak BTE. The Prius has a 1.5 liter engine, but it takes in air only 1.2 liter per intake stroke due to its over-expansion power stroke, so it's comparable to a 1.2 liter engine powering an almost 3000-lb car.
Posted by: Roger Pham | Oct 3, 2006 2:07:19 PM
Mr. Pham, I think you are refering to the maximal BTE of these engines. As you can see from this consumption/emissions model of the 1NZ-FXE, calibrated from test data, the peak BTE of the engine is roughly 37%.
http://www-personal.engin.umd.umich.edu/~chrismi/downloads/HEVModel/FC_PRIUS_JPN.m
The average efficiency during the EPA highway cycle is something like 20-25% because the car only requires ~15hp of the ~70hp the engine can produce. The 37% efficiency is the peak efficiency of that engine, but the engine is usually not operating at that level of efficiency, and drivers will not see it unless they engage in rather extreme driving habits. Or speed. ;)
Run the numbers compared to the EPA highway mileage yourself. The Prius glider needs, at most, ~8kwh to go 50 miles in an hour using the EPA highway schedule, but it uses roughly 33.6kwh, i.e. a gallon of gas. Which translates to ~24% BTE.
If Toyota had used a smaller displacement version, then perhaps more drivers could see the 36% peak efficiency at ~50mph, but Toyota knew that most drivers travel well over 70mph, so they optimized engine efficiency for much higher speeds instead of the EPA highway testing average of 48.3mph.
Posted by: yesplease | Oct 4, 2006 6:49:29 AM
Mr. Please, thanks for your seriousness in presenting data to support your assertion. Your approach is truly scientific. It is, then, in this scientific spirit that I would like to point out a few things in those set of data:
Below are the data from the link that you've provided.
(g/s), fuel use map indexed vertically by fc_map_spd and
% horizontally by fc_map_trq
% fuel use from Feng An's model calibrated with actual data for Prius_jpn (Atkinson cycle) engine
fc_fuel_map = [
0.1513 0.1984 0.2455 0.2925 0.3396 0.3867 0.4338 0.4808 0.5279 0.5279 0.5279 0.5279
0.1834 0.2423 0.3011 0.3599 0.4188 0.4776 0.5365 0.5953 0.6541 0.6689 0.6689 0.6689
0.2145 0.2851 0.3557 0.4263 0.4969 0.5675 0.6381 0.7087 0.7793 0.8146 0.8146 0.8146
0.2451 0.3274 0.4098 0.4922 0.5746 0.6570 0.7393 0.8217 0.9041 0.9659 0.9659 0.9659
0.2759 0.3700 0.4642 0.5583 0.6525 0.7466 0.8408 0.9349 1.0291 1.1232 1.1232 1.1232
0.3076 0.4135 0.5194 0.6253 0.7312 0.8371 0.9430 1.0490 1.1549 1.2608 1.2873 1.2873
0.3407 0.4584 0.5761 0.6937 0.8114 0.9291 1.0468 1.1645 1.2822 1.3998 1.4587 1.4587
0.3773 0.5068 0.6362 0.7657 0.8951 1.0246 1.1540 1.2835 1.4129 1.5424 1.6395 1.6395
0.4200 0.5612 0.7024 0.8436 0.9849 1.1261 1.2673 1.4085 1.5497 1.6910 1.8322 1.8322
0.4701 0.6231 0.7761 0.9290 1.0820 1.2350 1.3880 1.5410 1.6940 1.8470 1.9999 2.0382
0.5290 0.6938 0.8585 1.0233 1.1880 1.3528 1.5175 1.6823 1.8470 2.0118 2.1766 2.2589
0.6789 0.8672 1.0555 1.2438 1.4321 1.6204 1.8087 1.9970 2.1852 2.3735 2.5618 2.7501 ];
[T,w]=meshgrid(fc_map_trq, fc_map_spd);
fc_map_kW=T.*w/1000;
fc_fuel_map_gpkWh=fc_fuel_map./fc_map_kW*3600;
%Eff
%0.13 0.20 0.25 0.28 0.30 0.31 0.33 0.34 0.34 0.34 0.34 0.34
%0.14 0.21 0.25 0.28 0.30 0.32 0.33 0.34 0.35 0.35 0.35 0.35
%0.14 0.21 0.26 0.28 0.31 0.32 0.33 0.34 0.35 0.35 0.35 0.35
%0.14 0.22 0.26 0.29 0.31 0.32 0.34 0.34 0.35 0.36 0.36 0.36
%0.15 0.22 0.26 0.29 0.31 0.33 0.34 0.35 0.35 0.36 0.36 0.36
%0.15 0.22 0.26 0.29 0.31 0.33 0.34 0.35 0.35 0.36 0.36 0.36
%0.15 0.22 0.26 0.29 0.31 0.33 0.34 0.35 0.35 0.36 0.36 0.36
%0.15 0.22 0.26 0.29 0.31 0.33 0.34 0.35 0.35 0.36 0.36 0.36
%0.14 0.22 0.26 0.29 0.31 0.32 0.34 0.34 0.35 0.36 0.36 0.36
%0.14 0.21 0.25 0.28 0.30 0.32 0.33 0.34 0.35 0.36 0.36 0.36
%0.13 0.20 0.25 0.28 0.30 0.31 0.33 0.34 0.34 0.35 0.36 0.36
%0.12 0.19 0.23 0.26 0.28 0.30 0.31 0.32 0.33 0.34 0.35 0.35
%Min bsfc = 224
%Max Eff = 0.36
Please refer to the link itself for the actual appearance of the matrices, because when I copied them over, the 12 x 12 rows and colums arrangement are lost.
1) The data are obtained in 1999, from earlier model of Prius for which Toyota has listed the tank to wheel as being 32%, in consideration of the losses in the drive train. The 37% efficiency from tank to wheel that I quoted is referred to the 2004 Prius or later, from which substantial improvement in efficiency was realized.
2) Noted that maximum BTE of 36% is obtained quite early on at relatively low rpm and low fuel consumption of only .9 g/s but at high volumetric efficiency (near wide-open throttle). Note that the maximum fuel consumption of 2.7 g/s at maximum rpm is associated with a BTE of 35%, not bad, but note that this is three times the horsepower of the maximum BTE at lower rpm. Now, look at the 9th column second row for fuel consumption, and the value 0.6541 g/s is shown. Look in the BTE matrix at 9th column second row, and this corresponds with 35% BTE. Divide 0.6541 by 2.7 and you'll get 0.24. So, let's say that maximum power is 75hp and 24% of max hp is 18hp, you'll still get a BTE of 35%, NOT BAD, ain't it. 18hp is the right hp level required for cruising at ~60mph or higher. At 50 mph cruise, the hp requirement is lower, let's say 14-16, and now, look at column 8 second row, a BTE of 34% is still available at 1/5 of maximum power (16hp). Please note that even though BTE of engine is lower at 50mph cruise, but aerodynamic drag and drive train friction will be a lot less, so the well-to-wheel data won't change to below the 32% number that Toyota has quoted.
3) The 2004 Prius should be more efficient, I suspect engine BTE is > 40%, allowing a well-to-wheel efficiency of 37%. So, by the same logic, cruising at 50 mph with lower engine BTE but lower friction loss, OR cruising at 60 mph or above, with higher engine BTE but also higher drive train friction, and your well-to-wheel number will not be lower than the 37% that I've quoted.
Your number of the Prius' engine BTE of 25% at highway cruise is NOT SUPPORTED by the EXPERIMENTAL DATA that you've provided. But, thanks for the wealth of data that you've referred me to. You have the approach of a good scientist.
Posted by: Roger Pham | Oct 7, 2006 7:31:53 PM
Ah, I gotcha. Well, it seems to specifically depend on what rpm the Prius is at during the EPA cycle. What's the minimum rpm the Prius can cruise at from ~50-55mph? If the car can stand say, idling down the freeway, <800@50-55mph, that'd be outstanding because pumping losses would be minimized as load is maximized. Unfortunately, I don't think this is the case, because of the trade off wrt drivability so to speak.
For example, here's a tidbit about the average highway engine speed I found Googling.
"It can be done in a minimally instrumented Prius by watching a tach --keeping RPM between 1400 and 2200 at highway speeds, and more like 1200 and 2000 at lower speeds. If you have a vacuum gauge, the observed range starts as vacuum drops to 5 in-Hg or lower as demand increases, and tops out before it sinks lower to 2 or 3 while crossing 2300 RPM."
So if the engine speed is between 1.4k and 2.2k rpm. On the high side, that's half of the max engine speed, and using your example as a reference, would correspond to ~31% BTE. Now, the thing is, bouncing around on the freeway would probably result in less than ideal engine efficiency because of the changes in load needed to accelerate/decelerate according to the EPA highway schedule, which explains why the EPA highway mileage is only 51mpg, but some can get ~60+mpg with the cruise control at ~50mph, and others can get upwards of 70mpg by pulsing up to some target speed, and gliding back down to another, with the same approximate average speed.
More importantly, it begs the question, what is the average engine speed compared to some average speed, and how much can it be optimized? In terms of peak BTE, from what I've gathered, there's not much that can be done, so I'm guessing all improvement between first and second gen came from improved engine loading wrt transmission/engine speed. For instance, the 1VZ-FE has a minimal BSFC of ~237g/kwh, which corresponds to ~34% BTE, and this was an engine introduced in 1993 iirc, so the greatest improvements in gasoline engine efficiency have come during partial load, not from an increase in peak BTE. I don't think peak BTE has changed much between the 1NZ-FXE used in the first and second gen Prius', as opposed to maximized engine load from reworking the whole system, as well as a reduction in the CdA.
I'd love to see a 1L turbocharged Miller cycle Prius with ~30-40 miles of plug-in range, since that would minimize pumping losses even further, resulting in 30+% efficiencies at even lower speeds. While allowing for the same peak power output with the potential of even greater peak BTE. For instance I've "heard" that VW's TDI line is capable of 40+% BTE thanks to turbocharging, but in any event, I still don't think the Prius is seeing 35% BTE at ~50mph. I'd love for you to dig up some stuff on the CVT since I haven't been able to find much concrete info, and on that note... The ball's in your court. ;)
Posted by: yesplease | Oct 8, 2006 3:59:03 AM
One more thing, if the Prius has an overall tank to wheel efficiency of 37%, why does it only get ~55mpg during the EPA highway tests? Shouldn't it get something like 80+mpg?
Posted by: yesplease | Oct 8, 2006 1:54:25 PM
Ah, Mr. Please, thanks for the additional bit of data. The "1200-2000 rpm for cruising at lower speeds" seems about right. There is no actual rpm data posted on the U of Michigan Prius engine testing website, but it's seems that the second row data would correlate with engine rpm somewhere at 1200 to 1500 rpm. The second row of the matrices correspond with highest BTE at lowest power output at the lowest possible rpm.
The "trade off WRT driveability" that you are referring to would be valid in a 4-speed transmission, wherein you don't want to lug the engine to the max while cruising, because you won't have any available torque reserve at that rpm if you wanna accelerate even a little bit. Your throttle is already opened pretty wide, such that pressing further down on the gas will not cause much of any further acceleration. Your transmission will have to immediately downshift to 3rd gear with any kind of extra torque demand, but, doing so continously will wear out your transmission clutches and shifting mechanism. So, in a conventional fixed-gear-ratios transmission, you must cruise at ~above 2000 rpm and run the engine at ~35% of maximum volumetric efficiency in order to have the torque and power reserve for acceleration without downshifting. This will lower your BTE quite a bit, and you're right, to below 30%.
HOWEVER, this is a true CVT in the Prius, in which they can afford to have the engine lugged down as much as possible to bring out the maximum BTE. If acceleration is required, the simulated gear ratio will be immediately downshifted with infinitely-variable ratio WITHOUT any clutches or valves hence nothing to wear out, and the engine will immediately speeds up to deliver the higher torque required for acceleration. The engine can pretty much maintain its maximum BTE throughout its usage thanks to the electrical CVT and hybrid drive train.
How does Toyota HSD does it? The impedance on the circuitry of the starter/generator (SG) of the HSD is assigned the task of controlling the torque demand from the engine. More load on the SG will lug down the engine to simulate high gear, and less torque on the SG will unload the engine to simulate lower gear. You step down on the gas, and the SG will ease the torque load on the engine, allowing the engine to rev up and spinning the SG much faster than before, thereby sending a higher current to the traction motor thus multiplying the torque at the traction wheels that are driven partially by the electric motor and partially by direct torque from the engine in a power split planetary gear set that is the central part of the HSD.
You doubted that the BTE can't be improved in the Prius engines from the first generation to the second? You've just provide the info that the BTE of the 1VZ-FE engine 1993 model was ~34% and that was improved by the 1NZ-FXE to 36% circa 1997-1998. From 1998 to 2004 is a long stretch of time, such that improvement from 36% to ~40% BTE is not unreasonable. Toyota website has listed the improvement of the 1st gen Prius efficiency of 32% to the 37% efficiency of the 2nd gen Prius, and since the peak BTE of the 1st gen Prius engine is only 36%, it must follow that the BTE of the 2nd gen Prius engine has improved enough to bring the tank-to-wheel efficiency of the 2nd gen Prius to 37%, along with improvement of the drive train efficiency. Even with 50% efficiency improvement of the drive train, the resultant overall efficiency improvement tank-to-wheel is only but 1-2%, since drive train loss is but a few percents of the entire losses.
Posted by: Roger Pham | Oct 8, 2006 2:37:29 PM
Mr. Please, the following is a link to Toyota's website that lists the Prius tank-to-wheel efficiency, in case you have doubt :(
http://www.toyota.co.jp/en/tech/environment/fchv/fchv12.html
Posted by: Roger Pham | Oct 8, 2006 2:53:28 PM
For someone who's in the scientific spirit, you sure are pushing the data a bit hard in the direction you want to go. For instance, claiming that
"The "1200-2000 rpm for cruising at lower speeds" seems about right."
with no verification isn't very scientific. I asked around and was pointed to this Prius driving simulator.
http://www.wind.sannet.ne.jp/m_matsu/prius/ThsSimu/index_i18n.html?Language=en?Country=US
After fooling around with it, you'll notice that the average rpm during the EPA highway cycle (average speed of 48mph) is something like 1600-1700rpm. Definitely not 1200-1500rpm.
As for why the car must be at that rpm for drivability, if the vehicle were say, idling down the freeway at 1000rpm, then because it uses a CVT transmission, instead of a delay when the car would normally be shifting between gears, there is a delay because the ECU must inject more fuel in order for the engine to rev to roughly 4000rpm. The lower the transmission is while cruising on the freeway, the longer that gap will be between when the car is cruising, and when it is making peak power. Anecdotally, Toyota decided that having the car running at ~1700rpm@48mph was suitable for agreeable acceleration on the highway. Even though ideally it could be running at something like 1000rpm.
Now, in terms of the energy required for the car to go down the freeway at an average of 48mph, if what the Toyota website shows is true, then, since there are 33.6kwh in a gallon of gasoline, in order to be 37% efficient tank to wheels, the Prius glider itself would need .37(33.6kwh)=12.43kwh to go 51miles@48mph, according to the EPA highway mileage. So, the vehicle itself needs roughly 12.43kwh/51miles=243wh/mile at 48mph. Which, without context seems o.k.
With context, it's a bit out there. Take, for example, an S-10 converted to EV.
http://avt.inel.gov/pdf/fsev/eva/s10.pdf
At 45mph it uses 214wh/mile. And since the controller and motor aren't perfectly efficient, probably something like 80% efficient, the S-10 glider probably only needs ~.8(225wh/mile)=180wh/mile at 48mph. So, if the Prius is indeed running at 37% efficiency, then it needs 50wh/mile more than a two ton pickup with the aerodynamics of a brick, er, pickup.
If this is the case, something's fishy. Otoh, if we look at the Prius' stats in terms of Crr, weight, and CdA, then we find something interesting, and a bit more plausible.
Google returns that the Prius has a Cd=.26, and reference/frontal area=2.16m^2. It comes with LRR tires, which on the high end, supposedly have a Crr=.1, and the low end .06, so .08 seems reasonable. It weighs ~3000lbs with the driver, and the speed we're at is 48mph for the EPA highway test. Looking at the sum of the rolling and fluid friction, we come up with an instantaneous force
of (13350N).008+.5(1.225kg/m^3)(.26)(2.16m^2)(21.5m/s)^2=
107N+159N=266N, and the energy needed at that speed to go 51 miles is 266N(21.5m/s)=5.72kwh. or 5.72kwh/51miles=112wh/mile, or assuming the 8kwh figure I mentioned earlier (aircon, lights, and stereo on at full blast, rough road, etc...) 150wh/mile. Now that seems reasonable, that a lighter, more aerodynamic vehicle with LRR tires needs ~110-150wh/mile compared to a 4000lb pickup, which needs ~180wh/mile at the same speed.
Unfortunately it also means that the Prius is only operating at (112-150wh/mile)/(634wh/mile)=18-24% tank to wheels efficiency during the EPA highway cycle. Not 37%. If I were a speculative person, which I am, I would guess that someone in PR picked up on the peak efficiency of the 1NZ-FXE and ran with it as the tank to wheel efficiency. But who knows, maybe the Prius does in fact require more energy per mile than a two ton pickup truck. That would certainly be a feat of engineering...
;)
Posted by: yesplease | Oct 13, 2006 2:41:54 AM
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 ?? ;-)
Posted by: Gagar | Oct 13, 2006 6:25:46 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 | Oct 15, 2006 5:13:54 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 | Oct 15, 2006 8:05:52 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 | Oct 15, 2006 9:13:44 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 | Oct 15, 2006 9:41:45 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 | Oct 16, 2006 2:48:06 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 | Oct 17, 2006 4:38:59 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 | Oct 19, 2006 8:13:07 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 | Oct 29, 2006 1:46:41 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 | Oct 31, 2006 2:38:22 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 | Oct 31, 2006 2:42:02 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 | Nov 6, 2006 8:35:13 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 | Nov 6, 2006 1:13:04 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 | Nov 9, 2006 7:30:33 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 | Nov 14, 2006 3:55:26 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 | Nov 14, 2006 8:20:12 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 | Nov 19, 2006 7:12:09 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 | Nov 29, 2006 8:21:01 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 | Nov 29, 2006 3:40:55 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 | Dec 1, 2006 10:02:08 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 | Dec 15, 2006 9:51:09 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 | Jan 3, 2007 1:44:15 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 | Jan 3, 2007 2:01:12 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 | Jan 3, 2007 2:01:14 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 | Jul 30, 2007 12:38:35 PM
H2 is a very small molecule, able to escape from just about any containment we try to store it in.
Sizeable numbers of H2 powered vehicles in the global fleet will inevitably burden the atmosphere with quantities of free H2 which we have no previous experience of.
Has anyone considered what the this will do for the environment ? - I know that H2 kills some soil bacteria very efficiently.
Posted by: Ronseal | Sep 27, 2007 8:27:12 AM
This is a good.I don't know all of the science to this
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