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EV WORLD EXCLUSIVE ARTICLE |
Interior of Stuart hydrogen electrolyzer that cracks hydrogen and oxygen from water (H20). The author contends that making hydrogen this way wastes a lot of electricity; energy that could instead be used to power a battery EV or plug-in hybrid AND power most household electrical loads. Watch Video.
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Hydrogen skeptic Alec Brooks looks at the inefficiencies of making hydrogen from water to power a fuel cell vehicle.
Open Access Article Originally Published: September 24, 2004
A favorite vision for hydrogen powered transportation in the future is that hydrogen would be produced by electrolysis with renewable energy. System diagrams often show an electrolyzer next to a graphic of a windmill or solar array to symbolize that the hydrogen will be "green". Such an approach is said to provide zero emissions driving with no greenhouse gas emissions. It is certainly feasible to hook an electrolyzer up to a solar array or windmill – but the question is whether this is the best use of the energy.
The problem with making hydrogen with electricity is the large amount of electricity that is wasted. Fully three quarters of the electricity used to make and compress hydrogen is lost in the process; the electricity coming out of the fuel cell to drive a vehicle's motor is only one quarter of the energy used to make the hydrogen. This begs the question as to whether there might be alternate, less wasteful uses of this energy.
In a recent Los Angeles Times article, writer Dan Neal described his experiences driving a Honda FCX fuel cell vehicle fueled by hydrogen made at Honda's solar hydrogen fueling station. He was struck that a vehicle could be propelled by energy from the sun.
He rhapsodized, "I'm driving pharmaceutical-grade California sunshine: hydrogen generated in an experimental solar-powered station at Honda R&D America's facility in Torrance", and "I'm driving on pure hydrogen, the converted essence of the sun itself."
He went on to explain that Honda's large solar refueling station was designed to generate enough solar energy to produce hydrogen sufficient to drive the FCX about 10,000 miles a year. This works out to about a half a kilogram of hydrogen a day, good for up to 28 miles in the FCX. Honda's published data for the solar refueling station shows that it takes about 64 kiloWatt hours (kWh) of electricity to produce, purify, and compress each kilogram of hydrogen.
So on a daily basis, 32 kWh is consumed to make 1/2 kilogram of hydrogen. Of that 32 kWh, only about 8kWh is provided by the fuel cell system to run the vehicle's drive motor; the other 24kWh is wasted.
Studies comparing hydrogen fuel cell vehicles to other alternatives often have comparative bar graphs showing well-to-tank efficiency and tank-to-wheels efficiency. These measures do not promote a good understanding of the real situation.
What really matters is how much energy a vehicle uses per amount of distance traveled -- a function of well-to-tank efficiency and vehicle fuel economy.
Vehicle fuel economy is an all-inclusive measure of utilization of energy stored in the vehicle per unit of distance traveled. Tank-to-wheels efficiency is an imprecise concept, and is not a very accurate measure of vehicle energy consumption. Vehicles with very efficient engines can and often do get poor fuel economy.
To illustrate how the 32 kWh consumed every day to make hydrogen could be used more effectively, consider electrical loads that are familiar on a daily basis.
First off, we'd like to provide the same 28 miles of transportation electrically. With a battery electric vehicle or plug-in hybrid vehicle of the same size as the FCX, it will take about 0.30 kWh/mile for battery charging, or 8.4 kWh for 28 miles. This leaves 23.6 kWh (about three quarters) of the energy left over to be used for other purposes. With an overall energy budget of 23.6 kWh, all of the following common household loads can be served using energy efficient appliances:
- Run ten compact fluorescent light bulbs for 5 hours
- Provide the daily energy needs of the refrigerator
- Run the television for 4 hours
- Run the computer for 4 hours
- Run the dishes through the dishwasher, including electrically heating the water
- Run a load of laundry through the washer, including electrically heating the water
- Dry the load of laundry (gas dryer)
- Heat water for four showers
- Run a 3-ton (36000 btu/h) central air conditioner for 5 hours
This is a lot of utility and illustrates just how much energy is squandered in the hydrogen vehicle route. The comparison is simple: Use 32 kWh to (a) run a hydrogen fuel cell vehicle for 28 miles, or (b) provide energy for all of the functions above PLUS run a battery electric or plug-in hybrid vehicle for 28 miles.
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39 comments so far...
11-Jul-2006
28036
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I currently have two14x48 300miliamp soller panals on my boat,my batteries stay charged even after running my 1,000 wat seterio system all day,and my computor at night,I put a speacial oil in the bateries to stop any discharg of any kind.
I purchased an oxy hydrogen generator that only needs 15 amps to produce enough hydrogen to run my boat 50% more eficient,another thing that will try next is pluging in a cool mist humidifier into my power converter and directing it into the intake or carberator.also maybe I will add some h 2 o 2 to my humidifier and see what happens.why not use all the natural resourses and don't be so nerrow minded.and use comon sence
Posted by: kent hampton
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24-May-2006
22171
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I wish I had the link right here but I have read that they "scientists" are working on a solor cell that bypasses the electrolisis and makes hydrogen from the cell. That may be our answer to hydrogen as an energy carrier/fuel. I kow that they have already make one so far, but like many prototypes......it is still in the works. Personally I think we are way behind on our search for new technology. If we wait till gas is 3.00 a gallon, than we maybe deserve it! (Yes I know all of this has been in the making for a long time, but now there is pressure to get it ready)
Posted by: Jared jared
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29-Sep-2004
4870
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ICEs are discouragingly efficient if you're not a heat engine fan*. That's truth I feel should be more often told, rather than letting continue the error most recently repeated here by Dave Donis.
Thus Honda's recent achievement of having an unaffiliated reviewer drive a non-heat-engine hydrogen car 157 miles without refuelling was noteworthy; but hydrogen burners were going 186 miles more than 25 years ago.
--- Graham Cowan, former hydrogen fan
how personal mobility gains nuclear cachet
*So for instance, one Subaru motor
that serves both in cars and,
in a slightly different configuration,
in light aircraft does 0.39 lb/hp-hour
in car service at 2,700 RPM
(http://archives.glastar.org/0202/msg00120.html);
I get that working out to a TD efficiency of
33.2 percent."
Posted by: Graham Cowan
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29-Sep-2004
4881
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Why do we have to power a vehicle with fuel cells
in the first place? Why cannot hydrogen be used
to power an internal combustion engine. The
piston does not care if it is pushed by exploding
hydrocarbons or exploding hydrogen as long
as it gets pushed. Second point, has there been
any research into building a vehicle totally
from lightweight plastic. Instead of burning
off hydrocarbons to power a heavy vehicle made
from metal, lets use the hydrocarbons to make plastic and perhaps use far less hydrocarbons to
power the plastic car. Do not laugh, there are
some very high strength plastics and composites
available today.
"
Posted by: John Boyd
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29-Sep-2004
4884
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Total efficiency, from "well" to "wheels," does seem to be a nasty problem for fuel cell vehicles.
As I read it, this article estimates that 25% of the source energy makes it to the wheels. Another estimate puts the figure at 12%. www.efcf.com/reports/E03.pdf
This four conversion chain seems typical: source energy -> electricity -> hydrogen -> electricity. In that case, the limits on the "well to wheels" efficiency would seem, at best, to be in the 15 to 20% range.
A serial hybrid with a gasoline (or better yet, diesel) engine powering an electric motor would seem to promise much better, maybe even topping out at 40% "well to wheels" efficiency.
Anyone have some good numbers on what a serial hybrid can do?
"
Posted by: Edward Durney
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30-Sep-2004
4885
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Alec makes some good points. Electricity SHOULD be used whenever possible. If the wind is blowing and your lights are off, maybe it should go for electrolysis. Why not? The electricity is wasted if the demand is low. But electrolysis, despite its inefficiency, does produce value. Hydrogen is about 5X denser (and much lighter) than batteries. The storage is cheaper too (tank vs. battery). If you then react the H2 with CO2 (making methane), then you have a 16X density increase. DENSE FUELS HAVE VALUE. So you are producing value, provided you use the fuel wisely (like in a plug-in hybrid). If people are willing to spend more money on a laptop computer versus a desktop, with the same features, they should understand that concentrating energy into a denser source has value."
Posted by: Jim Beyer
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30-Sep-2004
4890
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But electrolysis, despite its inefficiency, does produce value.
The question from me is 'inefficiency as compared to what?
Since it has been established that electrolyzers and batteies have the same efficiency in terms of storage of electrons, and as stated the h2 when used as a feed stock for other fuel or fertiliser compounds has a marked value added effect, we need to get beyond the distorted perception that somehow electrolyzers are inneficient energy hogs. They are not and it will be proven out in future projects that require the storage of renewable energy to make them dispatchable and therefore competitive with fossil fuel electrical generation. To paraphrase Mark Twain 'reports of electrolyer inneficiency have been greatly exaggerated."
Posted by: larry Elliott
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30-Sep-2004
4891
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A vehicles on board battery can electrolize water to produce hydrogen and oxygen, the hydrogen can
then be used in the internal combustion engine and
the oxygen can be returned to the battery to recharge the battery in a re-oxygenation
process."
Posted by: John Boyd
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30-Sep-2004
4892
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Oh, about the inefficiency of electrolysis. This inefficiency shows up as heat, so why not perform electrolysis as a form of CHP in conjunction with, say, a water heater? Using electricity for heating is perhaps treason, but renewable electric (for heating) is probably cheaper than any renewable fuel that would be used for the same purpose."
Posted by: Jim Beyer
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30-Sep-2004
4893
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Larry,
I do not agree with your statement "It's still 85% efficient in terms of stored electrons" on HHV. The correct definition for efficiency is that based Gibbs free energy of combustion if you want to have an energy efficiency of 100% for a reversible process. With HHV, the reversible electrolysis would have 125% efficiency, and the reversible fuel cell would be 83% in efficiency. This is not a right definition. You probably noticed that the fuel cell people hate to use efficiency based HHV, while electrolyzer venders love it. You can understand why.
When people talk about round trip efficiency of 85% for battery, it is the energy released by the battery divided by the energy consumed during the charge process. You cannot compare it with the efficiency electrolyzer or fuel cell alone. You have to use the product of the efficiencies of the electrolyzer and the fuel cell. Here, the efficiency definition should be consistent - as long as you are consistent, the result is still correct even if you use the wrong definition for efficiency, such as that based on HHV. That is, if you use HHV for electrolyzer, then you should use HHV efficiency for fuel cell as well. As long as you are consistent, you will get the right number. For example, if your electrolyzer HHV efficiency is 85%, and your fuel cell HHV efficiency is 35%, your round trip efficiency is 0.85 X 0.30 = 25.5%. This is the number you should use to compare with the 85% round trip efficiency of the battery.
In practical world, most people have problems in understanding Gibbs free energy, while enthalpy of combustion is a lot easier to handle. That is why LHV instead of Gibbs free energy is used in defining efficiency by fuel cell people. Fortunately, these two numbers are very close for H2: LHV is about 2% higher than Giobbs from energy of combustion for H2. That is why even LHV efficiency is also a wrong definition strictly speaking, nobody has serious issues with it.
"
Posted by: Jianguo Xu
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30-Sep-2004
4894
| |
Jim,
Have you learned Carnot theorem? If not, the efficiency of a heat engine is smaller than 1 - To/T. Here To is the ambient temperature, and T is the temperature of the heat source. If your electrolyzer works at 350 K (77 deg C) - that is the heat source temperatuere, and your ambient temperature is 300 K (27 deg C), then the efficiency of your heat engine will be smaller than 1 - 300/350 = 14%. Smaller in this case is really "much smaller" since you need heat transfer DT in the reboiler and condenser if you use a Rankine cycle. A typical DT is greater than 10 deg C on each end. That alone brings the maximum efficiency to single digit. Add the inefficiency in the pump, the expander, the generator..., eventually you are lucky to have 5% efficiency in converting that low level to mechanical energy. You will have a tough time to pay for the equipment with that kind of efficiency. That is why you do not see a lot of power plants relying on heat at that low level for power generation."
Posted by: Jianguo Xu
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30-Sep-2004
4895
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"and your fuel cell HHV efficiency is 35%" should be "and your fuel cell HHV efficiency is 30%" in my first post here."
Posted by: Jianguo Xu
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01-Oct-2004
4902
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Jianguo Xu: Sorry, I didn't mean to try to use the waste heat for a heat engine....just heat! Just to pre-heat water for use in a water heater or something. Heat exchangers at these temperatures are pretty simple, and it might scavenge a few watts. That's all.
How hot do electrolyzers get? Anyone know?"
Posted by: Jim Beyer
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01-Oct-2004
4905
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Sorry, Jim. I did not read your post carefully enough.
I guess you could as long as there were a demand for that much hot water. Let's say you need to generate 5 kg of H2 a night by electrolysis. Assume the electrolyzer has a LHV efficiency of 60%, you generate 33.5 x 5 x 0.4/0.6 = 111 kWh of waste heat. That's a lot of waste heat. Give you an idea, if your electricity price is $0.1/kWh, the equivalent cost of electricity for generating that heat is $11.1 a night. I do not know how many houses spend that much energy in heating water alone. Not many I believe."
Posted by: Jianguo Xu
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02-Oct-2004
4910
| |
On a recent Scientific American Frontiers TV
documentary on fuel cell vehicles, a fuel cell
powered car was demonstrated. One scene showed
a considerable amount of water and water vapor
being emitted by the tailpipe. Assuming fuel cell
powered cars will be in the millions, in the future, has anyone done any studies on the degree
to which roads and highways will be constantly
covered in water in the summer and ice in the
winter. This could be a possible driving hazard.
If the water emitted is vapor then this could be
a significant amount of water vapor in our cities,
possibly affecting weather conditions in an
adverse way. I know this is a little off topic
but it seems relevant to any discussion involving
fuel cell vehicles."
Posted by: John Boyd
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02-Oct-2004
4912
| |
Minus the h20 that goes up as simple vapor from a fuel cell and assuming the vehicle gets about 60 miles per kilogram you would be discharging less than 2 gallons of water in 60 miles or a little over 4.5 ounces of h20 per mile. That's about 1/2 of a soda can of water in 5280 feet. Not much of a water problem even if you had 500 vehicles pass in an hour. In addition that water could be saved and recycled for use in an electrolyzer and for a vehicle with a 6 kg h2 tank or 6 equivalent gasoline gallons, that's only less than 14 gallons of water or less than 120 lbs. As for a fuel cell vehicle future increasing our relative humidity, consider this. If an inch of rain fell on one square mile of land and assuming 10% evaporated and the rest went as ground water, you would see at least 12,000 gallons of water vapor discharged to a square mile of atmosphere or the equivalent of about 5247 kilograms of hydrogen consumed in that same square mile. At 60 mpkg it would take more vehicles than could be placed side to side and end to end in that square mile so the moisture issue is not really an issue at all. "
Posted by: larry elliott
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02-Oct-2004
4914
| |
I agree that the input energy in the production of hydrogen will never equal the output energy from the use of hydrogen itself. However we must look past this fact and ask ourselves, "Why we are using hydrogen in the first place?"
The simple answer is that hydrogen is a chemical enery carrier. It is the bridge that enables energy to be mobile in transportation applications. We cannot fit solar/wind/tidal/hydroelectric power sources in our cars. With respect to electric vehicles, the charging of the battery results in a certain amount of down time. With respect to hybrid vechiles, CO2 emissions remain. Fuel cells however can provide continuous opertion with minimal refueling downtime and when using renewables sources, they are emission free.
When looking at energy use it is important to take into account the application. If renewables were used to produce hydrogen to power stationary sources then YES I would have to agree that it is a waste. However if renewables are used to produce hydrogen for transporation applications it is not a waste. An emission free energy carrier is needed."
Posted by: Freddy Lam
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03-Oct-2004
4917
| |
Isn't aluminum lighter, safer, already electrolysed from its oxide using mainly renewable electricity, the way hydrogen someday might be?
Try the math. Necessary information on how many kg of tank are needed to contain a kg of liquid hydrogen, the most compact and therefore least massive form, can be found at www.visionengineer.com/env/h2_liquid.shtml and on this Magna-Steyr spec sheet.
Correction, some necessary information. You also need to know that the 68 L of lH2 in the 90-kg tank mentioned in the first one weighs 4.8 kg. The Magna-Steyr tank holds 9.5 kg.
Contrariwise, a 1-kg tank, perhaps made of sheet aluminum, can readily contain more than 5 kg of combustion-chamber-feedable Al bits, or more than 10 kg of Al2O3 from that chamber.
And for sure, there are just as many Al-burning cars in real-world service as H2 cars.
--- Graham Cowan
How individual mobility gains nuclear cachet"
Posted by: Graham Cowan
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03-Oct-2004
4921
| |
Larry: Your figures sound reasonable but are
true under ideal conditions. In Houston, my
location, the temperature is always over 90 degrees F. for half the year. Most of the water emitted from a fuel cell car would quickly
evaporate when it hits hot pavement, adding to
the already high humidity. In addition, traffic
is often very conjested and often at a standstill,
several times a week. The water from hundreds and
more like thousands of cars would quickly accumulate and freeze during winter months. Although this would be more of a problem for northern states."
Posted by: John Boyd
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09-Oct-2004
5052
| |
John in your coment about the water from bumper to bumper trafic on a freeway you forget that an electric vehicle regardles of the source does not use any energy sitting stil however an ICE continues to idell in trafic"
Posted by: Greg Martin
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10-Oct-2004
5060
| |
John,
I saw that as well. This was in Iceland, one of the few places where sufficient geothermal energy plants exist to produce the hydrogen. The question is, really, is there an easier method of producing the energy required while not destroying the local environment. The existing models of single-user vehicles do make this question problemmatic. Someone mentioned Niven's satellites, which isn't impossible. Brin suggested using heat from the sun to produce lasers (Sundiver) which could then be directed to collectors. This might be a technology that is possible in the relatively near term. I guess the point is that the existing approaches all are extremely inefficient and something speculative posed by SF writers begins to look almost reasonable.
Rick
Rick"
Posted by: Rick Donnelly
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11-Oct-2004
5072
| |
Jianguo used the figure of 80 degrees C.. This
is 176 degees F. which is basicly steam. I would
hate to be in downtown Houston, during our 90 plus
summers, surrounded by hundreds of FCV's emitting
steam. Greg, yes, EVs are the only solution for
the future. If society goes the FCV route, I think
we are only trading one set of problems, carbon
gas, for another, steam and iced up freeways."
Posted by: John Boyd
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11-Oct-2004
5077
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Wow! The last time I looked water boiled into steam at about 212 degrees at sea level not 176.
If a fuel cell future would raise relative humidity levels one percent (doubtful even if current miles traveled increase by a factor of five)who could ever notice it in of all places Houston?
And with simple recycling through a condensor there's a complete absence of any water vapor,cold or hot weather as explained earlier.
It seems BEV guys simply can find any and every problem that can come to mind with fuel cells, that are really not a problem. Now let's continue to ignore the REAL problems with the BEV and continue bashing FCV problems that don't exist. That's fun if not productive I suppose.
Sure glad we don't actually vote on these issues."
Posted by: Larry Elliott
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26-Sep-2004
4837
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Yes, electrolysers and fuel cells are energy hogs. Brooks is, I think, being too kind in saying they lose only 75 percent.
When I was still a hydrogen fan I would have said electrolysers and fuel cells are a straw man; the true virtues of the hydrogen economy are those of nuclear plants producing hydrogen by direct thermal proceeees such as sulfur-iodine, liquefying it, and distributing it to cars that burn it, in engines not very different from gasoline-burning ones. Indeed, in BMWs recent, impressive efforts, the same engine burns either.
Those are still true points; fuel cells, etc., aren't less of a straw man, or sham, for being backed by government, indeed, one could almost think fossil fuel tax revenues were the only thing on governments' minds when, none too gently, they nudge car company research departments onto tracks that seem nonthreatening to such revenue within the foreseeable future, or as this is commonly said, within the next ten or 15 years.
But what motorist wouldn't want hydrogen? Compared to gasoline, who wouldn't prefer a zero-local-emission fuel that is electrolytically generated on a megatonnes-per-year scale using electricity from renewable sources, and only demands about twice the tank space and 3.5 times the full-tank weight and already has seen long service as rocket fuel? And is safe enough to sit in cardboard boxes on the shelves of virtually every food store?
Maybe no-one. But maybe some perplexity has arisen: what grocery store sells boxes of hydrogen? How could a hydrogen reservoir be only twice as big, only 3.5 times as heavy, as for gasoline? OK, I'll break down: the fuel described is aluminum.
--- Graham Cowan --
How individual mobility gains nuclear cachet"
Posted by: Graham Cowan
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27-Sep-2004
4840
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I agree 100% with with Alec, there should be no waste in producing energy to power vehicules. Battery powered vehicules sounds better solution. Trouble is everybody is talking about, but no one does really something effective in that direction. So I decided to start a project for lightweighted car using batteries. We'll see in 1-2 years."
Posted by: Darko Sola
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27-Sep-2004
4843
| |
Since when has efficiency determined the success of a product in the marketplace? IC automobiles are horribly inefficient, but we've been using them for a century because the fuel has been abundant, convenient and affordable. If somebody develops battery technology that will take a car 350 miles and allow it to recharge in 5 minutes the question of what will come after oil will be settled. Until that happens, I would not shortchange hydrogen or any alternative fuel."
Posted by: Dave Donis
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27-Sep-2004
4847
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Figures can lie, and liar's can figure.
Although I would never call Mr Brooks a liar I must say that his being directly involved in the BEV world and having him see it come crashing down in favor of FCV's may cloud his presentation somewhat.
To compare the Honda FCX and its fueling system to anything approaching maximum obtainable efficiency is somewhat amusing. Especially amusing in light of the fact that the entire system is still at Model T stage in its evolution. Honda engineers and others working independently have already demonstrated real world electrolyzer efficiencies of over 85% and there is still room to grow. That's as good as most any batteries in terms of true real world efficiency. Use a 500 or 750 bar electrolyzer and compression losses no longer exist. Remember, battery or h2, we are only looking to transport electrons. Although real world efficiencies of the PEM fuel cell will always be under 50%,(ICE's at less than 18% and yet they are ubiquitous) comparing them to batteries, even the highly touted lith-ion that has a long laundry list of shortcomings in spite of the hype, is comparing apples with oranges. An affordable vehicle is based on economy of scale more than any other factor. To obtain reasonable vehicle costs they must be mass produced in large quantities. The key is the word mass. They must have mass appeal to Joe who lives in icy Vermont as well as Don who swelters in Texas heat, They must also have utility meaning they must be capable of carrying more than a bag of groceries. In addition they must use a fuel that can also reach economies of scale in its production and delivery. Although a BEV's fuel, electric current,has already reached this level, the BEV cannot and will not since it is only applicable to smaller lightweight vehicles which means heavy vehicles will need another fuel source. And let's get real. American drivers have become used to power,speed and utility and have very little regard for efficiency. To supply an alternative that can have mass appeal is an extremely long row to hoe. So far it looks like Toyota and Honda are making good progress on that front with their fuel cell prototypes.
A mix of Hydrogen hype by one group and hydrogen bashing by another has become almost fashionable. I hear many of the same complaints toward h2 as I heard about solar PV or wind power in the early eighties. They even have a simlar ring to early computer bashers. Now they are all mainstream in spite of all the nay sayers who generally formed their opinions based on limited knowledge or just pure bias. Hydrogen will go on to fill its role in the future,what ever that may be, just as batteries will. Personally I would propel an electric vehicle on any source of electrons that proved practical. At present hydrogen and fuel cells still look like the better choice in the final analysis in spite of any numerical evidence to the contrary."
Posted by: larry Elliott
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27-Sep-2004
4850
| |
Larry stated that electrolysis is about 80% efficient and that is equivalent to batteries. That is incorrect. Batteries are 85% to 90% efficient at charging and discharging. Therefore Batteries can deliver 70% to 80% of the power that was originally used to charge them. At best fuel cells can only deliver about 40% of the energy used to make the hydrogen. Charging the battery is a concern. One company announced that they had developed a battery that can be charged in about 5 minutes. This will work great for small portable devices but I doubt it will be used in cars because the power requirement would be very high. Using the 8.4kWh battery in the article, to charge it in 5 minutes would require 100kWh supply.
A plug in hybrid would solve the charging problem at a cost effective price without any technology breakthrough. The hydrogen economy would require a breakthrough in storage, and a breakthroughs in fuel cell cost and reliability.
Recently a company by the name of Changing World Technologies has developed a process that converts organic mater to oil the same way the earth does but in only a few hours. Their first commercial plant is converting 2 tones of turkey scraps from the Butter Ball turkey plant into 500 barrels of diesel oil per day at a cost of $15 a barrel ($0.36 a gallon without tax). According to an article in Discover Magazine about the process, all the Agriculture waste the US produces in one year would produce about as much oil as we import today. The process has also been tested with sewage, plastic, tires, and medical waste. Add agriculture waste to that and we wouldn’t need drill for oil. An economy based on biomass is called the carbohydrate economy.
This technology combined with plug in hybrids could eliminate our need for fossil fuels without any technology breakthrough and at a cost-effective price today. The hydrogen economy cannot compete even if the fuel storage and fuel cell problems are resolved. The cost to manufacture hydrogen is simply too high. Pollution would be the only concern with a carbohydrate economy. According to the Union of Concerned Scientist, approximately 60% of all pollution in California is from diesel engines. Until recently diesel exhaust was not regulated. If all diesel engines had to meet the same pollution requirements as cars today and most future cares were plug in hybrids we wouldn’t have a pollution problem.
"
Posted by: Steven Franchuk
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27-Sep-2004
4851
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Larry shows how figures can lie. An 85% efficient electrolyzer has efficiency referenced to the higher heating value of hydrogen produced. An 85% battery/charger combination is referenced to the DC energy back out of the battery. IF you had an 85% electrolyzer that produced hydrogen at 5000psi it would take 46.4 kWh to produce one kg of hydrogen. With fuel cell efficiency a little less than 50%, you would get 16 kWh back out, or 35%. OK, so with a really good electrolyzer, you waste only 65% of the energy, not 75% as with today's systems.
I admit that it was apples and oranges comparing the Honda FCX to a 300 Wh/mi EV. The FCX is current technology; the 300 Wh/mi EV is a Toyota RAV4EV, designed in the mid 90's. A modern day Honda EVplus fitted with Honda's much improved electric drive motor and lithium batteries would come in at around 240 Wh/mi and would have MORE driving range than the FCX. (EVplus with current tech: 240 Wh/mi; FCX with current tech: 1143 Wh/mi; FCX with 85% electrolyzer: 829 Wh/mi). Granted the EV won't refuel as fast as the FCX; if you need fast fueling a plug-in hybrid makes a lot more sense than a fuel cell vehicle. Of course fuel cell vehicles will get better over time; but so will battery electric and plug in hybrid vehicles.
Larry closes with: "At present hydrogen and fuel cells still look like the better choice in the final analysis in spite of any numerical evidence to the contrary." This pretty accurately sums up California's thinking in forging ahead with hydrogen highways.
"
Posted by: Alec Brooks
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28-Sep-2004
4855
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Alec, I think my objective in the closing sentence was to illustrate the need for focusing any debate on FCV's vs BEV's on a mix of numerical as well as less easily defined total systems analysis.
A case in point would be your reference to the HHV or higher heating value of h2. Yes it is correct that the 85% is based on HHV (for the non engineer types who read this forum HHV is the energy content of a fuel before the latent heat of vaporization is subtracted. In simple terms it is the extra energy needed to create the water discharged by the fuel cell) yet that in no way lowers the actual energy contained in the tank. It's still 85% efficient in terms of stored electrons. Now let's take a look at the great lith ion battery. Energy in versus energy out does not tell the whole story. Just the not so simple end of life recycling issue is a case in point. The more common monopolar types in use are considered very diffucult to recycle. If and when a workable bipolar type can be produced the diffuculties will go even higher. All of this recycling and reuse will take energy and will have losses that enter the waste stream. Can we numerically quantify this. Perhaps but it is diffucult. The numbers I have seen just for the cell balance circuit losses and active cooling needed in hot weather on lith ion are not insignificant losses.What are the efficiency losses when the vehicle has cold soaked at -5F overnight in Vermont or New York? How about vehicle interior heating in a FCV vs a BEV? Heating in a BEV is an additional loss at a time it can least afford it. Not so with FCV. In addition what will be the total efficiency of the battery at its half life or end of life. These are all factors that need to be looked at. My point is that unless a technology is looked at in terms of its total system, numerical data can be a source of confusion.
One point that is rarely brought up in any of these debates is the assumption that personal vehicle transportation should even be our primary mode of transport. Perhaps maglevs would prove to be far more numerically superior to any vehicle. Shouldn't we then all choose maglevs? The devil is always in the details and I hope that forums such as these help generate as many questions as answers as we make critical decisions about the future of any new technology. "
Posted by: Larry Elliott
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28-Sep-2004
4856
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Larry Elliot's comments show how the perfect can be the enemy of the good. The issues of recycling, cold weather performance, and end of life efficiency are valid concerns for BEVs, (and for FCVs for that matter), but they pale in comparison to the very fundamental thermodynamic considerations that Alec describes. An energy policy that favors FCVs almost to the exclusion of BEVs, when BEVs use 75% less energy, is an energy policy intended to avoid incremental progress that could threaten the status quo. With that objective in mind, Maglev may be adopted as the next promising technology once FCVs lose their lustre."
Posted by: Tom Gage
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28-Sep-2004
4857
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I agree with the points in this article, yet I am disappointed that the author does not acknowledge the benefits of the renewable energy-hydrogen system. I always thought that electrolysis would be a great place to dump excess energy when demand falls on a grid. If renewable energy ever became a more substantial percentage of our generation, we would need still need a way to match the demand with the generation. Because you cannot control renewable energy generation, why not control electricity demand with electrolysis? The only other option is to somehow cut renewable generation down to match loads, which is the real waste of energy."
Posted by: Matt Weaver
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28-Sep-2004
4858
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You _could_ ramp electrolyzers up and down to help match generation to load. But you could also ramp vehicle battery chargers up and down in the same way, and you would need only 1/4 as many windmills (and land use) to serve the same number of vehicles.
More details of integrating vehicles with the power grid can be found at
http://www.acpropulsion.com/Veh_Grid_Power/V2G%20Final%20Report%20R5.pdf"
Posted by: Alec Brooks
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28-Sep-2004
4859
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A question for Alec: Thus far, this discussion
has been about fuels in a liquid or gaseous state,
e.g. liquid or gaseous hydrgen or even petroleum
in a liquid state. Is there a solid fuel that
could possibly have more energy per cubic centimeter stored in it? Pound for pound or
kilogram for kilogram, a stick of dynamite has
more explosive power than hydrogen or liquid petroleum so why not develop an engine that could run on fuel in a solid state. Perhaps some form
of a nitrate."
Posted by: John Boyd
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28-Sep-2004
4861
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I haven't seen any good discussions of using fuel cells as range-extenders for BEVs. This could reduce or eliminate the very serious refueling time considerations many people have when they consider taking a long trip. It would still allow the vast majority of miles driven to be done with the higher efficiency battery storage of grid electricity. Additionally, you need a much smaller tank and fuel cell to power such a car, perhaps 15kW. Further benefits are that this is the logical extension of current hybrid cars, and that you're not strongly tied to any particular technology for your range extending generator. This way you can choose whatever generator works best for your location, which may ultimately be hydrogen, or not. Because it's an apples and oranges comparison, why does everyone insist on falsely requiring that we choose EITHER batteries OR fuel cells?"
Posted by: Chris Barnes
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28-Sep-2004
4862
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Hmmm...I think Alec is making a lot of sense with these comments. As far as Americans wanting a renewable fuel vehicle that really performs...wow! ...there already a lot of options?!
BEVs...high performance sport BEVs like the Tzero
Heavy trucks...biodiesel...of course!
Family haulers...E85 ethanol
We don't have to wait for hydrogen! I've cut my petroluem use RIGHT NOW by 75% with my 2003 VW Golf TDI running on biodiesel. The only virture I can see that a FCV provides over a BEV is the "possible" refueling advantage. The problem is, the latest Honda FCV is rated at 190 mile range. Who will build the network of hydrogen refueling stations every 100 miles so that the refueling "advantage" can be achieved? Without the network of fueling stations who will buy the cars? Without the cars...who will build the refueling stations?
If you are just using your FCV for round trip commuting...shoot! just get a BEV. Or better yet, buy a plug-in hybrid with a 20 mile all-electric range and have it be an all-purpose vehicle with plenty of existing infrastructure."
Posted by: Marc Franke
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04-Oct-2004
4963
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What larry is forgetting, that electricity can not travel long distance, and hydrogen can be transported any distance with less than 1% loss.
We can make hydrogen in the dersert, and pump it anywhere. Why do you think farmers in Germany are making more money from windmills than growing crops.
Lets put our deserts to work, and tell world keep your oill.
Also I agree, we are wasting our biomass, by burying it.
Kevin"
Posted by: kevin Michael
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07-Oct-2004
5018
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The conventional vehicle emits a lot of water, too. Most of it comes out in the form of water vapor. As a matter of fact, all of it other than during vehicle startup goes out in the form of water vapor. This vapor, however, can indeed condense or even freeze on cold days. The same is true of the water formed from the fuel cell reaction: the waste air will bring out a lot of the water formed in the form of water vapor. As a matter of fact, if a fuel cell is running at 80 deg C, and the cathode chamber is at close to atmosperic pressure, you will find that the fuel cell will lose water as more water will leave with the exhaust air in the form of water vapor than the fuel cell can produce! This will dry out the membrane and cause efficiency and other problems. When the cathode chamber runs at an elavated pressure, the situation can be different. In that case, you also have the problem of efficiency loss: the air has to be compressed and that consumes energy. That energy consumption can be a significant drag on the efficiency of the fuel cell.
Water hazard, if exists, is least of all problems fuel cell vehicle has. "
Posted by: Jianguo Xu
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15-Oct-2004
5137
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Hey everyone - thanks for continued input of these articles. I'm especially grateful for the opposing opinions. However it's sad I had to go hunting to find conversations like yours. The general public has NO IDEA what can be done with alternatives to ICEs - but you could tell them. If you spend your time trying to one-up each other, you might as well quit now.
C'mon guys, make some noise where it counts... news agencies & mainstream media are dying for real content. Write some letters, make some diagrams, send an email - find someone local to carry a story. If you lose the ego & provide an intelligent/honest voice beyond your little bubble I think people will listen. If not, it'll be left to amatuer hacks like me and we'll screw-up the message. "
Posted by: Jonathon Corbridg
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