good article. Those are dramatically lower figures
for platinum requirement than I've seen before.
Also no mention of the difficulties of operating
a PEM FC at below freezing temperatures. I assume
lack of space dictates the failure to address
the issue of a need for a factor of five increase
in life of the NAFion PEM membranes which currently
don't live beyond 1000 hrs. and are the subject
of much investigation. And I'd like to see some
evaluation tests of eg. 250 bar H2 fuel tanks
as terrorist explosive devices. Would you allow
one into the basement of your apartment building?
I also find the Ovonics fuel cell very interesting, essentially a NiMH battery adapted to pump H2 into the cells to supplement the H2 normally stored in it when operating as a battery. Uses no platinum catalyst. Tested to -20 deg. so far. Eliminates the 2 min. startup time of PEM's and can recover, store and return the regen braking energy in the fuel cell. Very rational at first view. http://ovonic.com/sol_srv/3_2_fuel_cell_sol/fuel_cel_solutions.htm
Ideal cycle for efficiency, however, is still the boron / oxygen engine.
|Sorry, of course I meant to say 330 to 660 bar H2 fuel tanks, not the 250 typical of CNG.|
|Thanks for the url on Ovshinski's latest Len. I had not gone there because Ovshinski has hyped so many things in the past that never quite got there that I have been turned off. It looks like he may have it this time, if Texaco is willing to invest heavily. I didn't find any data on storage by weight so would guess that there is srill some problem, but overall it looks promising. I didn't get into PEM temperature and lifetime issues because the technology is moving so fast that what you KNOW today will be wrong tomorrow. They don't put PEM fuel cells in a submarine with 1000 hr lifetime. Yeah, I'd allow a 5000 psi tank into my basement. The whole issue of storage by adsorption or absorption could take up another paper, and isn't really a subject matter for EnergyPulse. Murray|
Roger - I admit I largely buy the RMI "koolaid", but not without reason. The Prius is already a large part of the technology. Lotus has built lightweight fiber composite cars for years and sold them affordably (albeit expensively) even with hand layup. The only thing keeping carbon fibre cost high is lack of really high volume production. Mazda has a new Miata concept car almost ready to roll out with a carbon fibre composite body shell. Daihatsu had a concept car at the Jan. 2004 Tokyo motor show with a light weight body, hybrid drive, and claimed 140 mpg. Even though the starting raw material for a fibre composite body is much more expensive than sheet steel today, by the time the steel is cut, formed, cleaned, welded, and painted the body shell cost is pretty close to a fibre composite body with the color baked in, and the capital cost for the fibre composite body is much less than for the steel one. RMI has had their projections validated both by retired American auto engineers and by Lotus engineering. The big obstacles are entrenched thinking of current auto engineers and managers, who are a very conservative bunch, and the existing capital sunk cost. When the Japanese start selling the next generation lightweight hybrids in the USA, and the waiting lists are again long, Detroit again will reluctantly move in the right direction. It will probably take at least another 10 years, but the hand writing is on the wall. Murray
|Roger - I admit I largely buy the RMI "koolaid", but not without reason. The Prius is already a large part of the technology. Lotus has built lightweight fibre composire cars for years and sold them affordably (albeit expensively) even with hand layup. The only thing keeping carbon fibre cost high is lack of really high volume production. Mazda has a new Miata concept car almost ready to roll out with a carbon fibre composite body shell. Daihatsu had a concept car at the Jan. 2004 Tokyo motor show with a light weight body, hybrid drive, and claimed 140 mpg. Even though the starting raw material for a fibre composite body is much more expensive than sheet steel today, by the time the steel is cut, formed, cleaned, welded, and painted the body shell cost is pretty close to a fibre composite body with the color baked in, and the capital cost for the fibre composite body is much less than for the steel one. RMI has had their projections validated both by retired American auto engineers and by Lotus engineering. The big obstacles are entrenched thinking of current auto engineers and managers, who are a very conservative bunch, and the existing capital sunk cost. When the Japanese start selling the next generation lightweight hybrids in the USA, and the waiting lists are again long, Detroit again will reluctantly move in the right direction. It will probably take at least another 10 years, but the hand writing is on the wall. Murray|
|Oh yeah - one more point. Even if the initial cost for the lightweight car is high, I think that cost can be brought down much mote readily than can the cost of the fuel cells and the hydrogen storage. There are no technological issues, only financial and psychological ones. Murray|
|Richard J. McCann
|Your discussion of the criticisms of the new "hydrogen economy" misses several key aspects: - Using natural gas or coal as the fuel stock and/or electricity source defeats the primary motive for conversion--reductions in GCC related gases. As pointed out in the many of the articles, emissions could actually RISE. As for production form nuclear power, that production is already claimed and there is little prospect for significant new capacity. As for renewables, its unlikely that we'll add enough new capacity to meet our current growing electricity demand, much less adding the entire equivalent implied capacity of our transportation fleet. For comparison, the entire truck fleet of California totals more equivalent MW (60,000+) than all of the state's current electricity generation (45,000 MW), and that does not include the smaller automobiles and Class I and II light trucks. - Using automotive batteries for transportation is now an acknowledged dead end as projected production cost savings and life extension were not sufficient to make them economic except under extreme conditions. - Your presumption that FC costs will fall almost 90% to $30/kW are unrealistic. The huge implied increase in demand will send platinum prices skyrocketing (and leave us entirely dependent on only 2 nations for production--Russia and South Africa--so much for energy independence). Even today's diesel engines cost about $100/hp, and turbines cost $300/kW. - NRC has looked at the costs of increasing fuel economy substantially and found that the assumptions used by RMI, ACEEE and others are unrealistic. Politicians like to quote these optimistic numbers to that they can claim to be "green", but the truth is that they are economic pie in the sky. It's not just engineering interia that limits these technologies--economic history (learning by doing) tells us that the high initial costs are reflective of expected future costs. (And not to mention the toxicity issues related to substantial carbon-fiber production.) It is for these and other reasons that the skeptics have poked holes in the hydrogen dream.|
Repeated references to "hydrolysis", meaning splitting of water, are grating. Things that dissolve irreversibly in water are hydrolysed, i.e. broken by water. Breaking of water is beyond the range of meanings that word can usefully have. "Water-splitting" is a good expression to use, or if by electricity, water electrolysis.
I agree Bossel and Eliasson are too dismissive of liquid hydrogen, in effect knocking over a compressed-gaseous-hydrogen strawman. This is obviously a hazardous procedure!
Over the years many hydrogen cars have existed in the lab (cf. the hydrogen car timeline) and, to the best of my knowledge, no aluminum-burning ones.
But that just means aluminum-burning cars in real-world service are equally numerous with hydrogen cars so serving. Aluminum would be lighter and safer, and already is produced on a large scale using renewable energy.
--- Graham Cowan, former hydrogen fan
|Thanks for a great
article and perspective on hydrogen as an energy
medium. Coming from an independent power and deregulated
energy perspective, I am intrigued by hydrogen's
potential. I am confident hydrogen will be part
of a long-term solution to our energy needs. From
my perspective, hydogen is not an energy resource,
but rather is a medium to transport energy, much
the way steam is an energy transporter using water
as a medium. The fact that it takes other forms
of energy and associated environmental impacts
to produce hydrogen is not necessarily a bad thing
if the sum of all components results in a net
positive benefit (cleaner air and increased overall
energy resource efficiency). I think there is
more to the Hydrogen Economy than we fully appeciate.
Chapter 8 of Jeremy Riflin's book "the Hydrogen
Economy" struck an important chord in his reference
to a "Hydrogen Energy Web" where fuel cells paired
with hydrogen production are part of a network
of distributed generation and hydrogen sources,
working with existing utility distribution infrastructure
to exchange electric energy to and from a network,
much like the the way internet is a network to
exchange information. While costs may be high
today, the real frontier for hydrogen is development
of a viable storage process. Another challenge
we face is to bring hydrogen in line with other
energy applications. The economics of most energy
processes are measured on a energy conversion
heat rate (BTU/kWh or kJ/kWh), $/MMBTU (or $/kJ)
variable cost, and $/kW fixed cost basis, regardless
of whether for power generation, transportation,
or thermal (heat) process. A gallon of gasoline
has about 155,000 BTU/gallon (HHV) which at $2.30/gallon
(I live in California), works out to about $15.00/MMBTU.
I realize there is more to hydrogen than a simple
energy conversion, but it would be great to have
some numbers or analysis expressing hydrogen energy
processes on a net heat rate (BTU/kWh), $/MMBTU,
and $/kW basis.
Bob Hoffman Energy Dynamix Corporation
|Ah Richard, I do love those who know what can't be done. Interestingly the cost of wind energy fell about 90% in a decade or so. No big deal. The cost of a bit of DRAM memory has fallen 5 orders of magnitude in 30 years. There are dozens of universities and corporations and hundreds of very clever people busily beavering away to do precisely those things that you know can't be done. Who do you think will be right in the end? I'll bet on the very clever people. Please read my prior articles and watch for the next couple. You will be amazed! Murray|
like "And not to mention the toxicity issues related
to substantial carbon-fiber production." just
completely discredit your entire thesis. Do you
also believe silicon transistors will never be
developed simply because the process may involve
some toxic processes? And, the last time I checked,
no-one else ever mention toxic process in the
producing of carbon fibers. Producing poly-acrylic-nitrile
fiber base should be no more toxic than producing
the materials in most clothes. Alternatives based
on pitches use mainly carbon wastes from petroleum
processing or coal dust. Producing composites
is a long matured industry used currently to manufacture
everything from bathtubs to lawn furniture, and
I don't see why auto bodies should be any more
of a problem.
Of course, you auto engineers may know some secret reason why it is better to leave development of solutions to future problems to the Japanese or Europeans (or Chinese).
|Murray: It is an interesting coincidence that just today an announcement which I noticed on PhysOrg website but can no longer find, relevant to thermal electrolysis, eg see INEEL Hydrogen Website stated that they have demonstrated a 50% net thermal efficiency in producing hydrogen from high temperature electrolysis tests in a system which can be used with a nuclear reactor (apparently a gen IV type, not the current ones). Assuming they can get this operating and scaled up, I'm thinking the debate on "Where's the hydrogen Going to Come From" will be about done.|
|Actually the reason
I couldn't find it on PhysOrg was because it was
on E4Engineering, at E4Engineering
"We've shown that hydrogen can be produced at temperatures and pressures suitable for a Generation IV reactor," said lead INEEL researcher Steve Herring. "The simple and modular approach we've taken with our research partners produces either hydrogen or electricity, and most notable of all achieves the highest-known production rate of hydrogen by high-temperature electrolysis."
On re-reading, it appears they may not have actually progressed as far as I'd thought. Still, getting there.
Thanks GRL Cowan at Boron Blast - Boron a Better Energy Carrier for tips on posting links.
And I still think the boron / oxygen cycle engine beats hydrogen.
|If one assumes
carbon dioxide (CO2) is the optimum carrier for
hydrogen, then almost everything you have written
is true, but the final portrait would look much
different. Combining 4 hydrogen molecules with
1 carbon dioxide molecule in a Sabatier reactor
(nickel or ruthenium catalyst) produces 1 methane
molecule and 2 water molecules that can be recycled
to reduce your electrolysis water needs by 50%.
I suppose one could also entertain ammonia instead
(using N2), but though denser than hydrogen, it
is still an awkward fuel that has no infrastructure
either. Maybe we can consider ammonia if we can't
find enough available CO2.
The methane retains 80% of the original energy content of the 4 hydrogen molecules. Compared with the efficiency of electrolysis, this is a greater improvement in energy density for the energy expended, so it should definitely be done if the CO2 is available. A two-pipe system of CH4/CO2 (moving in opposite directions) moves energy more efficiently than a single pipeline of H2 because the molecule count is reduced by 50%, but the energy stored is reduced by only 20%. Because the gas behavior is dominated by particle count, not weight (remember PV = nRT ?), the heavier system of CH4/CO2 still takes less energy to move than the bulky H2.
There is plenty of CO2 for now, and more will be available later. Biofuel production alone produces enough byproduct CO2 (that is easily captured and carbon-neutral) to support millions of methane-driven vehicles. We just need the hydrogen. In the future, all the pure O2 that is a by-product of electrolysis can be used to facilitate CO2 capture at stationary plants (I can explain that more if anyone is curious).
The reason this will supplant any effort to building a pure H2 economy are threefold: infrastructure is already in place, the medium is 3.2 times denser energetically than H2, the system can co-exist with natural gas supplies.
H2 is a horrible fuel medium for vehicles. Even if a FC was 100% efficient (LHV), the storage requirements for hydrogen vs. methane would still be larger, even if the methane is burned in an engine that is only 33% efficient (LHV). So, all things being equal, a FC car will have less volume available to the customer. Efficiency improvements for vehicles are far more effectively accomplished with plug-in hybrids, which bypass the whole fuel creation issue entirely. Since a plug-in still has fuel powering it also (and thus range), it shares virtually all the benefits of an all-electric vehicle (including energy efficiency) with none of the drawbacks. All an automaker needs to build is a plug-in hybrid that can run on methane. Heck, maybe a small gas tank too. That's it. No fuel cells. No hydrogen. No infrastructure changeover.
At the risk of sounding patronizing, the problem with energy studies is that if just one piece of information is out of place, one needs to rewrite a whole strategy. Such is the case with hydrogen. If energy storage via carbon is the best strategy based on billions of years of evolution, who are we to question it? The answer seems clear to me (unless, of course, I've missed a piece of information).
|Who are we? We're
what billions of years of evolution produces when
it "wants", so to speak, to tame fire and make
heat engines. That's who.
Arguing from the authority of Nature will, if done consistently, take you some places you probably don't want to go.
--- Graham Cowan, former hydrogen fan
|Jim - I'm not knocking your idea, because I haven't previously thoight about it and don't fully understand it. My first problem is with the infrastructure. We don't have 2 way pipelines. However we do have a complex network so it would be possible to transfer CO2 one way and methane the other using different pathways, at least for some source/destination combos, but only after we no longer use these paths for NG. Getting the CO2 to the hydrogen, and the methane to the point of use is not obvious with the existing infrastructure. Then let us start with 10 quads of electricity ro generate hydrogen at 90% efficiency. Then combine the hydrogen with CO2 ro make methane that can be burned with 80% of the energy in the hydrogen. We now have 7.2 quads available as methane which we burn in an ICE at 33% efficiency providing 2.4 quads ro the drive shafts and maybe 2 quads to the wheels. We use methane for 70% of the travel and battery power from the plug in hybrid for the other 70%, with let us say 85% battery efficiency. We have 66% combined efficiency ideally, pretty close to what we can expect from the hydrogen system in a few years. However if we used hydrogen in a FC in place of the methane the 30% would be at close to 60% efficiency instead of 20 % and our combined efficiency would be 78%. Also we can use the existing electrical infrastructure to bring the energy to the point where we need the hydrogen, so no 2 way pipeline and no conflict with natural gas. If the source of CO2 is burning coal for electricity, I'm not sure we would have enough. I'm not a chemist and don't know how to work out the amount of CO2 we would get from 23 quads of coal, and how much hydrogen we would need to combine with it, and how many quads of methane would result. We would need at least 6 quads of methane to replace 30% of 28 quads of petroleum used for transportation now. If batteries are not problematic in other ways I can see the plug in hybrid having advantages, but I don't see how methane would be as good as hydrogen, especially after we run out of coal and don't have the CO2 source. It seems to me you are trying to cross a chasm in 2 jumps. Murray|
|Thanks for your
comments. I agree that using methane as an energy
medium is counterintuitive. There is an article
in www.evworld.com that touches on this.
Regarding infrastructure, the two pipelines would not need to be set up extensively in practice, only in a few select areas. As an example, consider the wind resource of the Dakotas, a good potential energy source for hydrogen production and which would be expensive to access via the electrical grid. If this hydrogen source was fed CO2 produced from biofuel plants located around and near that area, then only a few hundred miles of CO2 pipeline is needed. The existing NG infrastructure could pipe the produced methane out of that area to points west, east and south.
By your own calculations, FCs net 18% more efficency than methane if plug-in hybrids can be employed. But you need to be careful to base both systems on HHV, not LHV. The LHV for hydrogen is only about 82% of its HHV, compared with about 90% for methane (LHV/HHV). So if you are assuming 90% (LHV) efficiency on your fuel cells, this would translate into 74% (HHV). If I am following your calculations correctly, this puts the net efficiency of the FC back to 50% (instead of 60%) and lowers the combined efficiency to 75%. On the other hand, SOFCs (burning methane) could bring the methane vehicle up to 40% (HHV), for a combined efficiency of 72%. So this whole hydrogen infrastructure may only net us 3% more efficiency for our vehicles, certainly not the 2-3X efficiency improvement that some are claiming. I know Bossel-Eliasson rattled some cages, but their comments on the LHV/HHV issue are very important.
I understand this seems to be placing a burden on getting plug-in hybrids to work, but given the market introduction of regular hybrids, this seems a more likely bet than the near-term introduction of fuel cell vehicles. As an aside, the recent NAS study on hydrogen vehicles completely omitted plug-in hybrids entirely. I cite this as evidence of how dynamic this area is at present.
Finally, there is probably enough carbon-neutral CO2 to go around. There is potentially 15 quads of biomass available in the U.S., by some estimates. Only about 3 is used now, so let's assume we could get to 7 quads, just to be safe. If used to produce biofuel, that would produce 7 quads of fuel plus enough CO2 to support 7 more quads of methane. Probably enough to go around. Plug-in hybrids would help with this, as they would reduce the amount of energy (as fuel) needed by our vehicles.
Thanks for the discussion! I'd much rather be shown to be wrong than to remain wrong-thinking, so I think it's important to keep interrogating each other until we can figure this all out.
I think this was in the news a year ago. I don't recall just where the methane was supposed to get burned, but if it was in cars, there are some details that were, as far as I recall, only implied. I fill them in thus: to get back to the Sabatier reactor, carbon dioxide from a combustor exhaust port (through which it passes in fairly dilute form) is cooled to a temperature very near ambient, so cool that perhaps liquid CO2 condensation is possible (temperature well below the critical one of IIRC 31 Celsius). That would allow some degree of separation from nitrogen.
Kept in an onboard tank, the CO2 can be swapped for methane at a refuelling point, and from there travel through the return pipeline to the power station.
There are already a few thousand cars with compressed methane tanks. How would the onboard CO2 tanks compare in volume? I may get around to this arithmetic if no-one else does.
--- Graham Cowan, former hydrogen fan
|I think that adding to the existing electric grid is less expensive than building pipelines. Taking the electricity to where the Hydrogen is needed, and generating the hydrogen on site has to be easier than than moving CO2 to the hydrogen and methane back. Also we have significant parts of the country not served by NG pipelines, but almost the entire country served by the electricity grid. On the other side, using oxygen enhanced combustion, and the latest flue gas clean up technologies we can get a very highly concentrated CO2 stream for coal sourced CO2. I'm pretty doubtful about collecting CO2 on the vehicle for recycling. That seems too complex, and the simplest solutions are the best (Occam's razor peraphresed). Murray|
|"The cost of a bit of DRAM memory has fallen 5 orders of magnitude in 30 years." I love your can-do attitude!! Perhaps in 30 years we can turn hydrogen from a net energy sink to a net energy source. However I won't be holding my breath.|
|You don't need
any CO2 collection on vehicles. Vehicles account
for only 18% of our CO2 emissions (U.S.) and nearly
every other emission source would be easier to
capture than from a moving vehicle. See the Keith-Farrell
paper in the July-03 Science. We need to be concerned
about CO2 emissions from cars only when our other
emission sources have been fixed. They are all
lower hanging fruit. With respect to methane instead
of hydrogen, you just emit the CO2 from the car.
By definition, it is either carbon neutral (if
derived from biomass sources) or at worst twice-used
(such as from a coal-fired electric plant stack).
Either way, you aren't making anything worse,
and you are able to use a fuel that is 3x denser
than hydrogen and already widely used in our economy.
Regarding electric-based grid distribution of hydrogen -- that's fine, assuming the grid is always going. But if we wish to move to more renewable electricity, the grid may NOT always be going, at least to the extent needed to support vehicle fuel in addition to our electrical needs. If that's the case, you either need electrical storage or massive bulk hydrogen storage to accommodate the daily and even seasonal variation in our renewable energy sources. We obviously get more sunlight during the summer months, so if we wish to take advantage of this resource, we need some way to store it. Not for hours or a few days, but months. Since electrical storage (batteries) would be far too expensive, that leaves hydrogen gas, and a lot of it, much more than you could store at individual gas stations. Given that, finding, and perhaps moving a bit of CO2 is not so bad, because it would reduce THAT storage by a factor of 3 as well.
Regarding Dursun Sakarya's comment, of course making hydrogen (from electricity) is a net energy sink. It always will be. It will NEVER be an energy source, only a medium.
The point is STORAGE and TIME. If you want to use energy that was accumulated in the past, you need some way to store it. Hydrogen (or methane) is a convenient way to store energy, at least compared with electrical charge, or even chemical batteries.
This convenience comes at a price. Only 70 or 90 percent (or whatever) of the electrical energy remains in the hydrogen. But the storage cost is much lower, so depending on how long you need to be able to store the energy indicates how wise it is to create the hydrogen in the first place.
People seem to have no trouble understanding that a laptop computer should cost more money than a desktop computer of equal capability. With energy, the situation is the same. Higher density is more convenient and thus more valuable. Under the right conditions, making hydrogen from electricity can be a value adding operation.
|I think a lot
of the discussion is clouded by a lack of stating
clearly what time frame is being discussed. Murray's
article, I think, is directed to the very near
term eg. what is possibe in the next 10 to 20
years, whereas part of the debate is directed
much further out, eg. what will happen when fossil
carbons are no longer ever used as energy fuels,
a very different though inevitable proposition.
Discussing whether bi-directional methane/CO2 systems make sense in terms of the energy distribution infrastructure of today or the next twenty years is fairly pointless, it won't happen on a widespread basis. In 200 years? Who knows, maybe. But given todays pace of scientific development and extrapolating that far, I'd guess it's simply an academic exercise. Chances are that by then any energy requirement you can't collect from the globally available harmless microwaves beamed down from power satellites designed to mitigate the onset of the next ice age, can be gotten from your pocket fusion reactor / garbage recycler as necessary.
It's like asking George Washington to predict the optimum energy distribution infrastructure for powering the computers and cellphones of 2005, though even that understates the likely level of change given todays rate of communication and organization in scientific and technological research.
One thing that is fairly predictable is a large penalty for allowing carbon atoms to combine with oxygen. The way carbon nanotube developments are heading, i'd guess by then pretty much everything from your personal transporter to your 3D video display will be manufactured largely from pure carbon. Hopefully the price of the nanotube can be brought down for current $85,000 / kg.
|While it's true
that one can make methane from hydrogen and CO2,
one can just as easily make methanol. (Maybe a
little easier). Methanol doesn't carry quite as
much energy per molecule as methane, but it's
liquid at room temperature. That's a very significant
difference. CNG vehicles have been around for
a long time, but have never become popular--even
though NG was until recently a very cheap fuel.
Two problems have been the bulk and weight of
the CNG tanks, and the time and inconvenience
of refilling them. I.e., the same problems, on
a more modest scale, that compressed hydrogen
Since methane and methanol are equally suitable as fuel for an IC engine, or for reforming and fueling a high temperature SOFC, my question for Jim is why advocate methane rather than methanol?
|Len Gould: I don't
think this is an academic subject at all. A lot
of money seems to be being spent to try to get
hydrogen fuel cells to work. A lot of talk is
going on about how to build a hydrogen infrastructure
to support these vehicles. The recent CARB ruling
in California (completely ludicrous, in my opinion)
limiting CO2 emissions in vehicles is real, not
academic. These are all affecting people and some
businesses in real ways. Not academic at all.
Maybe we don't need CO2 (or hydrogen) pipelines at all. Maybe plug-in hybrids are enough and we can just use foreign oil for the remainder.
Maybe global warming is worse than we thought and we can't even do that.
Maybe plug-in hybrids won't work, so producing fuel from renewables IS important after all.
Who knows? But I think it is important to at least try to think some of these things through. If only to keep politicians from wasting more of our money.
But I do know that even if we do have fusion reactors or solar power satellites, we will still desire a dense, energetic fuel for some uses. But maybe by then, we'll have enough energy to just make JP-8 and be done with it ! :)
I have no trouble with methanol at all. I think
reasonable people can see the advantages and disadvantages
of either choice. If we do wish to use more methanol
in our vehicles, however, it's important that
we don't reform our existing (and dwindling) domestic
natural gas to make it. We must either make it
the hard way (out of electrolyzed hydrogen) or
perhaps import it from Qatar or some other NG
rich area that can reform it there and ship it
over on a tanker. Or maybe pyrolize biomass, but
that seems a little brutish to me.
It is kind of a crummy fuel though, about twice as bulky as gasoline, very poisonous, hard to keep the NOx and formaldehyde emissions down. I'm not saying it's liquid form doesn't trump these concerns, but I think there may be a reason why it hasn't been enthusiastically embraced to date.
If I remember correctly, converting from methane -> methanol or methanol -> methane both leave about 80% of the energy left over, so if you ARE making it from scratch it would be beneficial to figure out which one you want and to stick with it. Since our existing infrastructure does have some high efficiency combined-cycle gas turbines (58% efficient), there is probably a use for at least some methane. The obvious convenience of a liquid fuel can't be overlooked, however. I'm not (yet) impressed with methanol fuel cells -- a recent vehicle demonstration in Germany could only produce about 1.5 kwatts.
On the other hand, it is possible that with liquid fuels, there is no free lunch, and you are paying even for that. For example, consider ethanol vs. methane as a fuel product from biomass. Ethanol, being liquid, is obviously a more convenient fuel. But the fermenting process produces ethanol in a water mixture, so a drying step is needed, which can be up to 30% of the energy content of the fuel produced. If this step can't be improved, or perhaps implemented with a waste heat source, then the "cost" of this convenience (the fuel being a liquid) could be another 30% of energy needed. Based on that, a pressurized tank might pay for itself in a just hundred fillups or so. Methane, on the other hand, is more easily separated (energetically) CO2 if the biomass is subjected to methanogenesis by methanogens instead of fermentation by yeasts. Only about 5-10% of the energy content is needed for the separation of methane from CO2. There may be some issues with methanol in the same way, but I'm not sure. (I'm not 100% sure of this "liquid-fuels-are-not-a-free-lunch" thing, just a hypothesis....)
I think in general, if we can understand how to live with smaller chain hydrocarbon fuels, at least in theory, we will be less surprised if oil depletion accelerates in the future and forces our hand.
(probably talking too much......)
|Jim, I quite agree
about not using our existing natural gas supplies
to produce methanol. There may be exceptions,
e.g., in cases where a gas well is small and remote.
If it's uneconomical to build a pipeline to the
well, it might still be economical to convert
the gas to methanol, rather than flaring it. It
could then be shipped out by tanker truck. That's
one GTL approach. Another is to makes synthesis
gas, and use FT synthesis to form heavier hydrocarbons.
I think both approaches are under development
and maybe being used in various places.
Do you have any opinion about the ZECA approach to gasification? It starts out by "burning" any carbon or hydrocarbon fuel in a hot hydrogen atmosphere to produce methane. The methane is then reformed with CaO and water, producing CaCO3 and at least twice as much hydrogen as used to make the methane. The CaCO3 is then calcined to regenerate CaO and a pure stream of CO2.
What's interesting to me about that process is that it should work well with oil shale as the hydrocarbon input. We have lots of that around. If we combined it with electrolytically generated hydrogen from renewable sources, it would stretch pretty far.
It seems like there's a wealth of good possibilities. Fighting wars over dwindling oil supplies is criminally stupid.
|A short "PS" about saving methane for power generation in high efficiency CCGTs: I don't believe there's anything magical about methane as a fuel for these systems. In fact, the turbine stages actually work better on liquid fuel, because the fuel doesn't have to be compressed. The rise of CCGTs using NG is an accident of history: gas was cheap and had "no better use". Liquid fuels were (and are) more valuable for use in vehicles than for producing power. But if a renewable energy economy produced liquid fuels naturally, they wouldn't need to be converted to methane in order to fuel a CCGT for power.|
|I forgot. Another
argument for methane over methanol is storage.
If one can accept the 'value' of CO2 as a carrier
for hydrogen bond energy, then one would collect
it and send it back to energy sources. But if
the time of energy use varies widely from the
time of energy production, you may be dealt with
a significant CO2 storage issue. Since CO2 is
a gas (and always will be) then if the fuel itself
is a gas, you could perhaps make dual use of this
storage and transport mechanism. (Like Mr. Duffin
said, perhaps a single pipeline could transport
CO2 to an energy site for one part of the year
and CH4 back during another part of the year.)
Currently large amounts of CH4 are stored in underground
geologic structures. They could be used to store
CO2 as well. If you made methanol, you still need
all the CO2 storage and transport, but in addition
you'd need storage and transport for the liquid
fuel. Agreed, since it is a liquid, this would
be a more modest investment, but given the concerns
about MTBE, people might not be thrilled to have
underground tanks of methanol around either.
From what I can figure out, methanol is not nearly as bad as MTBE, because it does decay naturally and quickly in the enivronment, but it is not all that wonderful either. If your toddler drank a tablespoon of gasoline, she would get sick. But if it was methanol, she would either die or have permanent serious injury. Methanol in higher concentrations also does NOT break down naturally because it kills the microbes that would normally feed on it.
We also DO have the existing NG infrastructure. I just tore the old oil tank out of my basement, so it would be annoying if they decided to heat homes with methanol instead. :)
According to their own website, the ZECA system does not produce hydrogen that is pure enough to be used in PEM fuel cells without degrading their catalysts. Ridiculous! Using hydrogen is IC engine is the worst of all worlds : poor fuel density, poor efficiency, they even have no-so-great NOx emissions.
In general, the notion of hydrogenating to remove C-C and C-O bonds from a hydrocarbon is a good idea. It improves the ratio of energy/CO2 produced from combustion. In terms of what ZECA is doing on both the methane production side and the CO2 capture side, I'm not sure how efficient they really are. Both seem to require substantial heat input, which has to come from somewhere.
I'm more of a fan of hydrogenating biomass, because you still get a good fuel (methane, methanol, perhaps even a kind of biodiesel) and the result is carbon neutral. The ZECA system is a little vague about how the CO2 sequestering is going to work.
I think we really need to be honest with ourselves and put all our cards on the table.
Are we considering the move to hydrogen because of the concern about oil depletion or global warming?
If it is oil depletion, then we should look to fuels from biomass or coal, such as methane, methanol, and biodiesel (we probably can't make a LOT of this stuff). We should look at improving efficiency with hybrids and plug-in hybrids. If we can reduce our oil use by just 10% (with a glare that we can reduce it another 10%) that would send enough shocks to the supply side of the oil industry to settle things down for another 20 years or so. But no hydrogen is needed in this equation. As for our electrical needs, just keep building coal plants.
If it is global warming we are concerned about, we need to limit emissions from our coal plants. Vehicle CO2 emissions are a small part of the equation, and not the thing to be looking at. We need to figure out how to integrate renewable electric in our grid and build more infrastructure for this. At least enough to forgo additional coal plant construction (This is the Joe Romm belief.) We need to consider nuclear power again, and gauge the risk/reward of that versus global wamring. We need to conserve electricity. There is probably at least 10-20% hardship-free reductions in electrical consumption that could be instituted if we focused on this. It is mostly an educational effort, as a home or business is always interested in saving money on their power bills. Again, no hydrogen here either.
In my opinion, the best, safest, and cheapest method of carbon sequestration is to burn less coal, and leave the solid chunks of near 90% carbon in the ground.
|Jim: Your last sentence has certainly hit one nail on the head. By far the wisest method of carbon sequestration is to leave coal in the ground. US citizens should intend to be very upset with politicians and company management if in the next twenty or so years if it is decided they need to reduce CO2 emissions given the present attitude to coal-electric generation. Good luck.|
|Jim, it is not either /or. For me the main driver is declining supplies of NG and petroleum, not global warming. However, in the medium run the 2 are synergistic. We will burn more coal, and it is better to do so as cleanly as possible, but the result will be declining coaL AVAILABILITY ALSO IN LESS THAN 50 YEARS. That's what I meant about crossing a chasm in 2 leaps. Using coal in the short run is only the first leap, and doesn't get you across the chasm. There are a couple of reasonably economic ways to clean flue gases and leave relatively pure CO2, as well as generating some hydrogen. For me the best part of your thesis is to then use this CO2 and the hydrogen, plus probably supplemental hydrogen to make methane to serve the present NG infrastructure/demand and stretch the NG supply as far as possible, allowing more time for the ultimate transition to hydrogen. I haven't thought my way through this yet, but there is promise in the idea. Murray|
|Murray: I don't
quite buy it. Collecting CO2 and H2 at an IGCC
coal plant, combining them into methane, then
piping it out into the natural gas infrastructure
is (almost) entirely pointless. The only potential
gain is energy storage as NG rather than as coal,
and the reuse of the then-nearing-obsolescence
NG infrastructure. This is of course assuming
the conversion process is about as energy efficient
as electricity generation. Storing energy as coal
is far more efficient than as methane, and transporting
energy as electricity has far more potential for
efficiency, convenience and co-operation with
other more environmentally smart energy sources
than as methane. Think developing superconductors,
super highvoltage DC.
Given that the fossil carbons still wind up being dumped, and methane itself is a far more worrisome GHG than CO2, I just don't see the balancing benefit.
|Murray, if you
are mainly driven by declining NG and oil, then
we should further develop hybrids and plug-in
hybrids. If we can get plug-in hybrids to work,
then even renewable electric at 10 cents per kWhr
is cheaper than the gasoline it would displace.
Vehicle fuel is definitely easier to displace
economically than coal-generated electrical power.
I agree with Murray that coal won't last as long as people think, especially if it is used more aggressively. With respect to a fuel, you are better off just making methane from coal, and using that. Assuming you sequester the CO2 from the methane production process (NOT during the methan USE) you still save about half the CO2 that the coal would otherwise produce. You could replace that CO2 emitted (from the methane use) by sequestering a like amount of CO2 obtained from biofuel production. The potential for biofuel from cellulose is hopeful, and since the process produces much carbon-neutral CO2 as well, biofuel production can serve to utilize fossil fuels in a carbon neutral way further. Assuming large scale CO2 sequestering works. I'm a little skeptical about that. If you have one wellhead split open, you could kill a few thousand people downwind with a CO2 leak. That would give CO2 sequestering all the public confidence of a nuclear power plant.
I realize proposing to turn our cars over to NG sounds crazy, given our current shortage. But we have more NG around than we do hydrogen, which doesn't exist at all, and which is most commonly obtained from NG in the first place.
I'm trying to figure out what the two leaps are. I think the first is domestic energy independence, and the second is no carbon emissions. Is that close?
Electrical grids are not cheap, are only really economically practical for lengths under 300 miles or so, and depend on 24/7 use. We tried to size a grid needed to get the wind power from the Dakotas to Chicago. It's really hard. You either end up throwing away a bunch of electricity during peak times, or way oversizing the wires, making the transport of electricity ridiculously expensive. Another thing that people don't seem to understand is that renewable energy is completely different than our current system. Fundamentally so. Not necessarily worse, just different. It has to do with their intermittent nature, which is totally anti-thetical to the grid as we presently perceive it. But if we can learn to live with this, our ability to integrate these resources will be much easier for us.
Methane is not that much worse than CO2 as a GHG. True, it is much more heat absorbing, but it break s down (into CO2) after about 10 years. So over the life of the molecule, CH4 is only about 5X worse than CO2, not the 20X that people say. (That was another thing CARB got wrong.) Since CH4 is useful, presumably people will work harder to capture and use it rather than let it drift away.
I think a good experiment would be to develop some of the wind resources in the Mid-Central states. Use the energy to make hydrogen and then methane and probably some ammonia too. (Ammonia is the lowest hanging fruit for electrolyzed hydrogen, and producing it would reduce some of the methane use from that industry.) The CO2 is fed from nearby ethanol plants. (I'm not a huge fan of corn-based ethanol, but they are good sites to test out the process.) Congress just approved a massive NG pipeline to come down from Alaska, so the system could pipe into that. Depending on how much wind we capture, we'd end up producing a centrally-located, but very disperse methane source that would never run out. All of this would cost money, of course, but since so little gas would be initially produced, the overall price of NG would not go up very much.
In the short term, we need to conserve energy more and add smaller renewable energy sources locally that people can use. Plug-in hybrids are good for this because they can be plugged in perhaps 20 hours per day, so they have a good chance of getting charged from an intermittent source. We need to resist the urge to build more coal plants, because that's a 50 year committment of infrastructure to emit more CO2.
If our government is working to make us safer, it is hard for me to understand how spending another dollar on defense accomplishes this, versus spending that dollar on either increasing domestic energy production or increasing our energy efficiency.
|Jim: The "two
leaps" referred to are first, replacing petroleum
with coal-based systems, then eventually replacing
that coal-based system when the coal runs out.
Is definitely pointless if the "second leap" technology
is already known.
Your statement "electrical grids are not cheap... " etc just doesn't hold up. Compared to what? Anf you guys need to stop evaluating AC electrical as the only possibility (300 miles). HVDC at modern voltages can transport energy more economically than rail or pipeline and the greater the distance the greater the advantage. With articles such as F. Mack Shelor's at The Arguments for a National Direct Current Transmission Grid , or the proposal for a continental DC grid by Black and Veatch, and many others having been around for years, there is simply no further excuse for not fianlly bringing the grid into the 21st century and resolving all these issues. Or see my own proposal, the Active Electrical Transmission System
The limits of North-South NG transmission are already filled by Canadian production so building the pipeline from Alaska proposed by congress (only to the canada border) will either require an additional huge investment to get the gas from the Alaska-Yukon border into the markets or displacement of currently available production. Neither makes sense. This one should be held off until canadian production has fallen enough to allow it to use existing pipes. Problem is, that would require some creativity in how to expand energy production in the mean time. BTW, Canadian NG resources fell almost 5% last year despite record drilling.
|The only problem
with the "first leap" being the leap to coal,
is that if it turns out we have more coal than
atmosphere, we may never get to the second leap.
I am suggesting electrical grids are not cheap compared with pipelines. I am not suggesting to make a fuel from electricity, pipe it somewhere, and then convert it back to electricity in a power plant. That wouldn't be wise. What I am suggesting is that some electrical power could be 'stranded' which might be better off converted to some kind of fuel instead. And then use the fuel in a vehicle.
The problem with any type of electrical transmission grid (AC or DC) is that electricity can't be stored in it. A pipeline can accommodate different pressures to allow for some storage as well as storage in geologic structures, etc. If we wish to embrace renewable electric (sun, wind) then we need to think about the grid more carefully. The grid at present relies on flexible capacity to match demand changes. If the future grid is to accommodate renewable electric, it will have both the supply AND demand sides changing somewhat randomly. I don't think they are prepared for that. That's why utilies are reluctant to assign wind farms any percentage of base capacity. This is a much more serious problem than whether we should have DC vs AC transmission lines, in my opinion.
It may make sense for some amount of the power to come out of the Dakotas as electricity, but it would have to be a small percentage of the peak power production, well under 30%, I would think. Otherwise the transmission capacity would be wasted.
I thought they had approved funding for the entire pipeline, not just that section. My mistake.
Jim, believe me the entire NG pipeline network can't vary the pressure enough from min to max ro make much difference in storage. It might be 1% of annual consumption. You havent read the paper I published on wind. Intermittancy is not a problem in a geographically large well integrated grid, with modest back up storage. The storage can be hydrogen, or pumped hydro where that is possible. yeah, I am all for hybrids, and for plug in hybrids if batteries are not problematic (which I am not yet convinced of). Hybrids are a very important bridge to the HE as I thought I made clear in my paper. Murray
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