Is Hydrogen Economy Viable Without Fusion Energy?

[kmarinas86]

The only way a hydrogen economy would make sense is if it produced energy (e.g. via fusion).

Without getting energy from hydrogen, fuel cell vehicles and etc are basically overly complicated batteries.

 

[Ygggdrasil]

However, batteries currently are not very good at storing energy and electric vehicle cannot travel distances comparable to gas powered vehicles. Using hydrogen as an intermediary for energy storage could allow them to act as a better "battery" with a greater range than electric cars.

However, I do agree that a lot more work is needed on hydrogen in order to determine whether it will actually be feasible. As you correctly mentioned, an environmentally friendly hydrogen economy relies on the development of a renewable energy infrastructure as hydrogen only stores energy. Furthermore, its not necessarily clear that battery technology won't improve, and it may also be more advantageous to change our driving habits to support the use of electric vehicles.

 

[mgb_phys]

Without getting energy from hydrogen, fuel cell vehicles and etc are basically overly complicated batteries.

It makes sense for transferring large amounts of energy large distancess
If you have geothermal (iceland) or solar (n. africa) it is easier to make hydrogren and ship that to LA than run a power line or ship recharged nicad batteries.
The infrastructure is more easily modified, lots of natural gas and LPG technology.

It's not clear if hydrogen powered cars make more sense than electric. Power densities are similair and both need to improve if they are going to be more than around-town subcompacts. Hydrogen fits the gas-station fillup / oil company model but electric let's you recharge at home overnight.

 

[WarPhalange]

Also, even using oil or coal power plants to get electricity and store it in hydrogen is more efficient than using gasoline automobiles, because it's easier to stay efficient on a large-scale than to have every driver take necessary steps to make their car more efficient.

 

[russ_watters]

However, batteries currently are not very good at storing energy and electric vehicle cannot travel distances comparable to gas powered vehicles.

The way you worded it, it isn't true. Batteries store and recover energy at an efficiency of better than 90%. Fuel cells, depending on how the hydrogen is produced, only around 50%.

Using hydrogen as an intermediary for energy storage could allow them to act as a better "battery" with a greater range than electric cars.

Now the way that is worded, it could be true. Reglar batteries have some drawbacks, like weight, cost, nasty materials, and charging time. Fuel cells might be better in those respects.

 

[russ_watters]

Also, even using oil or coal power plants to get electricity and store it in hydrogen is more efficient than using gasoline automobiles, because it's easier to stay efficient on a large-scale than to have every driver take necessary steps to make their car more efficient.

That is true of battery-powered cars, but not true of fuel cell cars. Assuming probably too high estimates of 70% efficiency for both the electrolysis and the fuel cell, 60% efficiency for the power plant, and 90% for the motor, that gives you about 27% efficiency. A battery powered car loses about 7% in the power lines and the batteries, charger, and motors are all better than 90% efficiency. That gives a conservatively low estimate of 40% overall efficiency.

 

[Coin]

The point of hydrogen in the "hydrogen economy" is as a common medium for energy transport and storage. If you didn't understand this already then you don't understand the "hydrogen economy" enough to debunk it...

That is true of battery-powered cars, but not true of fuel cell cars. Assuming probably too high estimates of 70% efficiency for both the electrolysis and the fuel cell, 60% efficiency for the power plant, and 90% for the motor, that gives you about 27% efficiency. A battery powered car loses about 7% in the power lines and the batteries, charger, and motors are all better than 90% efficiency. That gives a conservatively low estimate of 40% overall efficiency.

That 7% sounds very optimistic, are you assuming the power was generated locally? What if the power was generated a long way away and was transported over long distance power lines, or was generated at some point in the past and stored? One assumes hydrogen, if it's treated like normal substance fuels, would be used this way, I don't know whether electricity can be transported and stored as easily or not...

 

[russ_watters]

That 7% sounds very optimistic, are you assuming the power was generated locally? What if the power was generated a long way away and was transported over long distance power lines, or was generated at some point in the past and stored? One assumes hydrogen, if it's treated like normal substance fuels, would be used this way, I don't know whether electricity can be transported and stored as easily or not...

I'm talking about the transmission lines themselves and it is about 7%:
http://en.wikipedia.org/wiki/Electric_power_transmission#Losses

And I factored that into the batteries but not the hydrogen because I assumed the hydrogen would be produced at the power plant. Electric cars will almost certainly be recharged at home.

 

[Topher925]

estimates of 70% efficiency for both the electrolysis and the fuel cell

Didn't MIT just have a "break through" by using a new catalyst and cathode to have electrolysis operate at efficiencies of around 90%? Current PEM fuel cells operate around 50% efficiency although I think Honda's (FCX) is approaching 60%. I can see this number being 70% in ten years. And although it isn't hear yet solar thermolysis shows promise of some extremely high efficiencies.

One overlooked aspect of batteries is their disposal. They don't last forever, and most high capacity batts don't last longer than 500 cycles. Also you have to consider that all batteries self discharge. BTW, if you compare the Honda FCX to the Tesla Roadster, they both have about the same max distance. But the FCX does cost a hell of a lot more.

 

[mheslep]

Didn't MIT just have a "break through" by using a new catalyst and cathode to have electrolysis operate at efficiencies of around 90%? ...

Yes. Uses common materials and is highly efficient. Should be, finally, a practical and economic way to use electrical means to store energy in chemical form (H2).
http://www.sciencemag.org/cgi/content/full/1162018/DC2
http://www.technologyreview.com/article/21179/page4/

 

[mheslep]

...and most high capacity batts don't last longer than 500 cycles. ...

That depends a great deal on the level of discharge, the top off charge, and temperature. If one mediates all these, which the Tesla roadster does and your laptop does not, the battery life will be greatly extended.

 

[Topher925]

...and your laptop does not...

My laptop has hardware designed to maximize battery fitness, doesn't yours.

Anyway, LiFe(P) has done a lot for battery durability but that comes at a pretty big hit of specific energy which in the long run kills efficiency. The lightest batts, Lipoly not Lion or LiFe(P), have very limited life spans even when properly used. I've never gotten more than 200 cycles out of my Lipos for my RC heli's while I could run NiMH for over a thousand.

 

[mheslep]

My laptop has hardware designed to maximize battery fitness, doesn't yours.

All the mfn's design to maximize operation time per single charge, as that's what is advertised and reviewed. Their first priority is to give you non-stop operation on that coast-to-coast air travel, lifecycle is an afterthought. Obviously laptops have no temperature stabilization on the battery. The Chevy Volt for instance will hold in reserve some percentage (10%?) of the battery charge, and they never top off the charge either, neither of which is provided by your laptop. Generally laptop charge circuitry is only tasked with limiting charge rates and Li ion safety issues.

 

[mheslep]

Of the several problems with an H2 economy by far the most intractable to my mind is the transportation and/or storage of H2 as a fuel. With some of the more recent developments I 've been musing that perhaps a solar/wind/grid based local roadside H2 station might start to make sense. Details below. First the problems w/ H2 up until now.

This chart lays it out nicely:
http://www.physorg.com/news85074285.html
To run an H2/fuel cell car, starting with 100kWh electric power one ends up w/ only 23kWh of tractive power delivered by the vehicle:
AC-DC: 95%
Electrolysis: 75%
Compression: 90%
Transport/transfer: 80%
Fuel Cell: 50%
Electric drive train: 90%

So far the logistics of providing roadside fueling of an H2 car has meant:
stage 1: a large electrolysis center somewhere w/ with a massive megawatt connection to the grid to make the H2 (or reforming from natural gas but let's drop the fossile source for this line). Then compression, storage, and transport to local road side stations. Note that it takes 15-20 tankers of compressed 3000 to 5000 psi H2 to deliver the energy equivalent of one gasoline tanker, and existing pipelines won't handle H2 at all.
stage 2: road side H2 station, storage again until delivered to the vehicle.

Now some musing on how this might be done differently, given recent developments:
-Nocera's efficient and cheap electrolysis breakthrough (linked above)
-Improving solar PV efficiency and technology, especially concentrated PV
-Electric transmission becoming more expensive and difficult.
These three lead me to the concept of a completely local, self sufficient H2 roadside station. Given: the average existing US gas station pumps 2000 gal/day. At 136Mjoule/gal-gasoline, that's 272000 Mjoule/day, or 76000 kW-hrs/day. Assuming the new H2/fuel cell cars are 3X more efficient than existing ICE cars, we need only a third, or 25300 kW-hrs/day of equivalent electrical energy.

Now, efficiencies. We need no AC/DC conversion. After 90% efficient Nocera on-site electrolysis and 90% efficient on-site compression we need 31234 kW-hrs/day. To get that from the grid means a 1.3MW average electric service at all 200,000 US filling stations, hard for both the local filling stations and the grid at large to accommodate, so let's try onsite generation.

Solar is a good fit here in a sunny climate because we're along side the highway, and because we don't care about variability. One just buffers enough H2 to stay ahead of demand. At a year round average of http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/" , have that kind of land to spare.

Cost? Solarbuzz says http://www.solarbuzz.com/statsCosts.htm" claims they'll be doing 7 cents/kWh in a couple years.

 

[Ygggdrasil]

Today's New York Times (http://www.nytimes.com/2008/08/27/business/27grid.html) had an interesting article about wind power that goes along the lines of mheslep's comment. Many wind farms have to shut down when the wind is too strong because they're generating too much energy for the power grid. This highlights a major problem with two of the primary sources of renewable energy (wind and solar): their outputs are highly variable and may not match peak times for energy demand. This is where hydrogen, as a means to store this energy that would otherwise go unharvested, comes in. This hydrogen could either be used as a buffer for days where the solar/wind generators can't meet demand and/or could be transported away for use as fuel.

Of course, there are still problems with transport and storage, but it seems like generating hydrogen may not be so much of an issue now. Personally, I think storing hydrogen in the solid state (e.g. as metal hydrides or adsorbed in nanomaterials) shows the most promise, but these solutions are still in the R&D stage.

 

[mheslep]

Yes efficient production of H2 would help the variability of renewable power like solar and wind in many applications but it doesn't by itself enable a nationwide solution. As that NYT piece shows, the power has to be eventually shipped over transmission lines from the wind belt or the solar belt to the demand areas - except for onsite bufferable problems like a fueling station.

 

[vanesch]

Given: the average existing US gas station pumps 2000 gal/day.

You mean your average highway station only has about 100-200 customers a day ?

 

[Topher925]

Non-baseload power generation is the biggest flaw with alternative power sources. I believe it was once estimated that wind power could never account for more than 7% of total power on the grid because of variability. The current bandaid for this is the use of flywheels, for example Beacon Power's flywheels: http://www.reuters.com/article/pressRelease/idUS174731+19-May-2008+BW20080519

I believe the only answer in the end will by an H2 economy.

mheslep, that article makes a strong argument but it includes a lot of unnecessary processes. H2 would obviously be created directly at the plant and then shipped, in which case the fast majority of the losses would be just to do to the transportation vehicle itself which given a few years of R&D will become pretty close to current electric vehicle efficiencies.

 

[mheslep]

You mean your average highway station only has about 100-200 customers a day ?

That sound reasonable, I actually pumped gas as a kid, but I don't know. I used US daily 390 million gallons of gasoline / 200000 US gas stations.
www.eia.doe.gov/basics/quickoil.html

 

[mheslep]

Non-baseload power generation is the biggest flaw with alternative power sources. I believe it was once estimated that wind power could never account for more than 7% of total power on the grid because of variability. The current bandaid for this is the use of flywheels, for example Beacon Power's flywheels: http://www.reuters.com/article/pressRelease/idUS174731+19-May-2008+BW20080519

20%.
www.20percentwind.org

No doubt there are many storage methods possible. Pump storage and hydro has been the traditional load levelling go-to for the industry, geography/terrain permitting. At the moment Compressed Air seems to be the darling of DoE (one plant in operation), perhaps electrolysis-H2-gas turbine at NREL (prototype).
http://www.eere.energy.gov/de/compressed_air.html"

 

[vanesch]

That sound reasonable, I actually pumped gas as a kid, but I don't know. I used US daily 390 million gallons of gasoline / 200000 US gas stations.
www.eia.doe.gov/basics/quickoil.html

It's funny. When I get to a highway station, I'm usually waiting in line with say, 1 or 2 customers before me, there are usually 6 - 10 lines, and it takes me about 5-10 min waiting time before it's my turn, so I'd say that we get a customer flow of about 5-10 customers/ 5 minutes, or 60-120 customer *an hour*. Now, I realize that this is not the same at 18 hr than at 2 am, but nevertheless...

 

[vanesch]

At the moment Compressed Air seems to be the darling of DoE (one plant in operation),

This seems one hell of a stupid storage, no ? You loose a lot of energy by adiabatic compression and cooling ! Or do they use a different technique (like keeping the hot air thermally insulated) ?

 

[Topher925]

As far as I know, they just pump air into caves which can behave as a huge heat sink. Yes it is a stupid inefficient way of storing power but you can store a LOT of it on the cheap. Its very unpractical to store, let's say, 20MWhs with some batteries.

 

[Ygggdrasil]

One idea that's been floated is around (vehicle-to-grid technology) is to use batteries in plug-in hybrids and other electric vehicles to act as a buffer by storing energy when demand is low and providing energy during peak demands. Of course, this won't work until electric cars become widespread, but it's an interesting idea.

http://www.sciencedaily.com/releases/2007/12/071203133532.htm

 

[mheslep]

It's funny. When I get to a highway station, I'm usually waiting in line with say, 1 or 2 customers before me, there are usually 6 - 10 lines, and it takes me about 5-10 min waiting time before it's my turn, so I'd say that we get a customer flow of about 5-10 customers/ 5 minutes, or 60-120 customer *an hour*. Now, I realize that this is not the same at 18 hr than at 2 am, but nevertheless...

Wow. Where, France? I've rarely (70's embargo maybe) seen that kind of load anywhere in the US. I suppose the 2000g/day average is quite light for those interstate highway ten pump stations and heavy for the mom/pop two pump stations.

 

[mheslep]

This seems one hell of a stupid storage, no ? You loose a lot of energy by adiabatic compression and cooling ! Or do they use a different technique (like keeping the hot air thermally insulated) ?

Yes that's the criticism. I wouldn't know the amount heat transfer to the surrounding rock over the time span - for wind it would be hours to a couple of days. I suppose the geology must be chosen carefully. The couple of existing plants use natural formations, perhaps modified.

 

[mheslep]

One idea that's been floated is around (vehicle-to-grid technology) is to use batteries in plug-in hybrids and other electric vehicles to act as a buffer by storing energy when demand is low and providing energy during peak demands. Of course, this won't work until electric cars become widespread, but it's an interesting idea.

http://www.sciencedaily.com/releases/2007/12/071203133532.htm

Some good work done on V2G by NREL as part of their wind program.
Poster:
www.nrel.gov/analysis/winds/pdfs/wind_phev_poster.pdf[/URL]
Paper:
[PLAIN]http://www.eere.energy.gov/afdc/pdfs/39729.pdf"
The authors show that with a large US fleet of PHEVs by 2020, the reserve capacity could ramp up to 250GW (25% of todays total grid capacity). That makes assumptions of 50% plug-in time, very capable PHEVs (60's), etc. (Figure 5).

http://spectrum.ieee.org/oct07/5630"

 

[russ_watters]

This seems one hell of a stupid storage, no ? You loose a lot of energy by adiabatic compression and cooling ! Or do they use a different technique (like keeping the hot air thermally insulated) ?

I don't see it as being any worse than pumped-water storage. The point isn't in the efficiency, it is in finding a way to store a vast quantity of energy. Since at night you have a vast quantity of wasted capacity, you may as well use some of it to do some sort of storage.

France is all nuclear - what do they do at night?

 

[mheslep]

I think Vanesch was pointing out that possibility of energy loss in compressed storage. The compressed, necessarily hot, air could cool in fixed volume storage to the point where significant energy is lost (PV=NRT). The worse that could happen w/ pumped storage is evaporation?

 

[mheslep]

FYI
http://news.cnet.com/8301-11128_3-10026958-54.html?tag=mncol;title"

A New Jersey company said on Tuesday it will invest $20 million over three years to develop an underground compressed-air storage system for wind turbines and other power sources, a sign of growing confidence in the technology.

Energy Storage and Power is a joint ventured formed by energy developer PSEG Global and Michael Nakhamkin, who designed the only compressed air-storage facility in the U.S.

With Compressed Air Energy Storage (CAES), air is pumped into underground formations, such as depleted natural gas wells or salt caverns, using a natural gas-powered machine. The pressured air is released later to drive a turbine to make electricity...

Battery makers also want to play at the grid MW level. A123 reportedly is the battery vendor for Chevy's PHEV.
http://news.cnet.com/8301-11128_3-9976421-54.html"

...Fulop said that batteries can meet utility needs for grid stabilization, where a large amount of electricity is needed for a short amount of time.

"The technology can do it. Now it's a question of building the systems," he said. "Megawatt-level systems are all about systems integration."

In addition to batteries, utility-ready energy storage systems require electronics and thermal management systems, he said.

though at $500-1000 / kWh of Li ion I don't see how batteries compete. Perhaps they're cheaper at that scale and when mass is not important.

 

[russ_watters]

I think Vanesch was pointing out that possibility of energy loss in compressed storage. The compressed, necessarily hot, air could cool in fixed volume storage to the point where significant energy is lost (PV=NRT). The worse that could happen w/ pumped storage is evaporation?

No, the worst that happens with pumped-storage is the efficiency of the pump is only 60%, which is about the same as the efficiency of a good compressor.

Compressor efficiency ratings are almost always at room temperature output, meaning they take into account the heat generated in the compression and lost in the storage.

Heck, what do you think happens to water when you run it through a pump...?

 

[mheslep]

No, the worst that happens with pumped-storage is the efficiency of the pump is only 60%, which is about the same as the efficiency of a good compressor.

Compressor efficiency ratings are almost always at room temperature output, meaning they take into account the heat generated in the compression and lost in the storage.

Heck, what do you think happens to water when you run it through a pump...?

Yes I understand there are necessarily losses in the act of storage and again on the recovery. I meant that while the storage system is loaded but idle, the compressed air system is still bleeding off energy as the cavern cools. Not so with elevated water.

 

[vanesch]

France is all nuclear - what do they do at night?

Well, you might be surprised, but most french nuclear power stations can follow load, they are not only working in baseload. They can ramp at 5% of nominal power per minute, as long as they stay between 30% and 100% of nominal capacity (below 30%, there are problems with Xe poisoning). They can even handle up to 10% "immediate" load change from their working point.

 

[russ_watters]

Yes I understand there are necessarily losses in the act of storage and again on the recovery. I meant that while the storage system is loaded but idle, the compressed air system is still bleeding off energy as the cavern cools. Not so with elevated water.

We're talking past each other. What I'm saying is that it is generally assumed that that heat is lost in a compressed-air system. If the stored air is "still bleeding off energy as the cavern cools" then that means it hasn't lost all that heat - that's a bonus, not a penalty.

 

[mheslep]

We're talking past each other. What I'm saying is that it is generally assumed that that heat is lost in a compressed-air system. If the stored air is "still bleeding off energy as the cavern cools" then that means it hasn't lost all that heat - that's a bonus, not a penalty.

Ah, thanks, I see your point.

 

[mheslep]

...I've been musing that perhaps a solar/wind/grid based local roadside H2 station might start to make sense.

It turns out that the paper by Bossel "www.efcf.com/reports/E21.pdf"[/URL], 2006, dedicated a section to just this subject so I'm revisiting this post to compare. Bossel demolishes transportation of H2 and then logically turns to on-site production:
[QUOTE=Bossel 2006]I. On-Site Generation of Hydrogen One option for providing hydrogen at filling stations and dispersed depots is on-site generation of the gas by electrolysis. Again, the energy needed to generate and compress hydrogen by this scheme is compared to the HHV energy content of the hydrogen transferred to cars. Natural gas reforming is not a sustainable solution and thus not considered for the reasons stated earlier...[/QUOTE]
Vanesch will like the next:
[QUOTE=Bossel 2006]Consider a filling station now pumping [B]60 000 L[/B][15850 gallons] of fuel (gasoline or diesel) into 1000 cars, trucks, or buses per day. This number is typical for service areas along [B]European[/B] freeways. In most parts of the [B]United States, many smaller[/B] filling stations are located roadside at freeway exits.[/QUOTE]60000L/day! Must have an on-site refinery! I had used 2000g/day for our 'smaller' stations.

Then on the efficiency of H2 vs gas fueled ICS vehicles, Bossel downrates my 3x efficiency advantage estimate to 1.5:
[QUOTE=Bossel 2006]...However, hydrogen vehicles are assumed to have a 1.5 times higher tank-to-wheel efficiency than IC engine cars [29]. [B]The frequently cited number of 2.5 cannot be justified any longer[/B] in light of the high efficiency of diesel or hybrid vehicles. In fact, the well-to-wheel studies of 2002 [8], [9] are based on lower heating values, optimistic assumptions of fuel cells, and disregard of the efficiency potentials of
diesel engines and hybrid systems. The shortcoming of LHV analyses is discussed in [30]. Furthermore, more recent well-to-wheel studies appropriately based on the higher heating values [10] do not identify hydrogen-fuelcell cars as the best transportation option. In fact, the efficiency of all-electric cars is three times better than for hydrogen-fuel-cell vehicles [31].[/QUOTE]I have not run down these references yet, no doubt some mention of variable displacement ICE and the like. Bossel does use the term 'potential' regarding high efficiency ICE, but point taken.

More:
[QUOTE=Bossel, 2006]Under the favorable assumption of a 1.5 advantage of hydrogen versus gasoline, 60 000 liters of fuel will be replaced by 12 000 kg of hydrogen per day. The
electrolyzer efficiency may be 75%. Also, losses occur in the ac–dc power conversion. Making 12 000 kg of hydrogen per day by electrolysis requires 25 MW of continuous power and 108 000 liters of water must be pumped and demineralized. Compression power is needed for storing the hydrogen to 10 MPa and for transfer at 40 MPa to vehicle tanks at 35 MPa. In all, to generate and store 12 000 kg of hydrogen per day, the filling station must be supplied with continuous electric power of about [B]28 MW[/B]. There are many sites in arid regions where neither the electricity nor the water is available for hydrogen production.[/QUOTE]My assumptions (vs Bossel): 3x better vehicle efficiency (vs 1.5), 90% MIT/Nocera electrolysis (vs 75%), no AC/DC conversion of DC on-site solar (vs 95%). Using my assumptions we have a 10.3MW (Euro size) fuel station. I only quarrel with his 1.5x vs 3x assumption at the front end: the numbers of Bossels on highly efficient ICE are beside the point, the 60000L/day figure must be [U]today's[/U] consumption figure using '1x' cars of ~30mi/gal, not tomorrows better ICE, so the H2 converted fuel station, still serving '1000 cars', 90mi/gal equivalent, would only have to pump the equivalent of only 20000L, not 40000L. So Bossel's grid driven traditional electrolysis station should actually require 14MW.

Regardless, the large power connection drives home the point about the difficulty of connecting to the grid further adds to the case for doing solar on-site. I hadn't considered the water load which is substantial.

 

[Kasper_NYC]

This article is really interesting:

The Economics of Small to Medium Liquid Hydrogen Facilities

http://www.rmwsolutions.net/pub3.pdf

Otherwise I don't see easy at all to keep the hydrogen liquefied in a tank in ours cars... and just compressed doesn't make too much sense to me either. I guess we are going to keep seeing hydrocarbons in our car for long more time.

From this Document: http://www.dotynmr.com/PDF/Doty_H2Price.pdf

"... A common 120-gallon compressed-air tank, which can store 0.57 kg of hydrogen at 15 atm., costs $730 [31]. At $1300/kg, this is 85 times as expensive as the diesel tank per energy storage, and it is 40 times more massive and over 200 times larger. Fifty (very large) 3000 psi aluminum scuba tanks could provide 10 kg of H2 storage for under $14,000 and only 750 kg [32]. Pricing data from the high-volume production of these tanks suggest high-volume production of 5000-10,000 psi tanks for storage of 3-8 kg of H2 might cost $600/kg of H2, which is about 30% less than suggested in an earlier study..."

Best.

 

[Topher925]

You have to look at the big picture when it comes to hydrogen storage. The tank itself might be cheaper for gasoline or diesel but you also need to include the fuel delivery system, including filters and a pump that operates at 100% output when ever the engine is running. Fuel pumps are known to fail along with being very inefficient and on many models fuel filters need replacing. A compressed tank of H2 should be a one time purchase with little or no maintenance through out its life. And while the tank may be heavier, the fuel it is carrying is definitely not. I don't have time to crunch the numbers but 50kwh of H2 will weigh a lot less than 50kwh of gasoline, including the tanks.

Honda has already shown that using compressed H2 can be done practically. Although a better method of storage is certainly welcome.

 

[mheslep]

You have to look at the big picture when it comes to hydrogen storage.

We have been.

And while the tank may be heavier, the fuel it is carrying is definitely not. I don't have time to crunch the numbers but 50kwh of H2 will weigh a lot less than 50kwh of gasoline, including the tanks.

No, in a road vehicle using steel tanks the H2 system will weigh a little more. Carbon fiber tanks can remedy that but they are $$$. More importantly, the compressed H2 tank volume is several times greater regardless of material, at least 3X at 10,000PSI assuming the vehicle needs only 1/3 the energy; if you want the same energy content as a tank of gasoline its ~7X more volume, i.e, a fuel tank with wheels.

Honda has already shown that using compressed H2 can be done practically. Although a better method of storage is certainly welcome.

I'd say they've shown it can be done, period. Honda's cost to make the car is >$200k last I read. For reasons discussed above, one needs to stay close to the one or two H2 stations in your area if you have such a car, and the stations are not practical either. I also suspect the long term reliability of the fuel cell and its operation in cold climates is still an open question.

 

[gmax137]

Well, you might be surprised, but most french nuclear power stations can follow load, they are not only working in baseload. They can ramp at 5% of nominal power per minute, as long as they stay between 30% and 100% of nominal capacity (below 30%, there are problems with Xe poisoning). They can even handle up to 10% "immediate" load change from their working point.

The US nuclear units were also designed for daily load follow. They aren't operated that way, because once built, they provide the cheapest source of power. The fuel is almost free, compared to oil, gas, or even coal. So the power companies minimize their cost by running the nuclear units at full power, 24 x 7.

 

[RMForbes]

Why store hydrogen? Steam Reforming systems and even simple electrolysis systems are already available that can produce adequate hydrogen on-demand. Most of the energy consumption to produce compressed hydrogen gas is used to separate, purify and compress the gas for storage. If the goal is to produce a clean more efficient vehicle there is no need to separate the hydrogen out. Just produce it on board.

 

[Mech_Engineer]

Why store hydrogen? Steam Reforming systems and even simple electrolysis systems are already available that can produce adequate hydrogen on-demand. Most of the energy consumption to produce compressed hydrogen gas is used to separate, purify and compress the gas for storage. If the goal is to produce a clean more efficient vehicle there is no need to separate the hydrogen out. Just produce it on board.

Perhaps you could tell us all where the energy comes from to produce the hydrogen on-board in the first place?

Be warned that if you say "from burning some of the hydrogen on-board" I may end up having a slight aneurysm.

 

[mgb_phys]

Why store hydrogen?...If the goal is to produce a clean more efficient vehicle there is no need to separate the hydrogen out.

The goal is also to use hydrogen as a storage and transport mechanism so that energy generated a long way from the customer, geothermal in Hawaii or solar in Arizona, or intermittently, such as wind, can be used economically. Hydrogen is really more of a battery than a fuel.

 

[mheslep]

Why store hydrogen? ...

Reforming CNG etc presupposes that CNG is your energy carrier. The idea behind the 'H economy' is that we get off fossil fuels and in that case how do we move energy around? It turns out fossil fuels are great energy carriers in BTU/lb and BTU/gal. Certainly electric power is a big part of that answer, but then 1) how do you handle variable electric power from wind, solar, etc., and 2) how do you store energy on anything disconnected from the grid e.g. vehicles.? As Greenspan said, the electric utilities 'have no inventory'.

Most of the posts in this thread discuss proposals and problems w/ either 1) or 2)

 

[Mech_Engineer]

It turns out fossil fuels are great energy carriers in BTU/lb and BTU/gal.

More important than the fact that fossil fuels have large amounts of energy per volume, is that the energy has already been captured and stored in them. If we manufacture Hydrogen for energy storage and transport purposes, we have to get that energy from somewhere.

Hydrogen : Oil :: Empty Gas Tank : Full Gas Tank

Hydrogen can be used to store and ship energy yes, but that energy has to be acquired and put into the Hydrogen first.

 

[mheslep]

More important than the fact that fossil fuels have large amounts of energy per volume, is that the energy has already been captured and stored in them. If we manufacture Hydrogen for energy storage and transport purposes, we have to get that energy from somewhere.

Hydrogen : Oil :: Empty Gas Tank : Full Gas Tank

Hydrogen can be used to store and ship energy yes, but that energy has to be acquired and put into the Hydrogen first.

Yeah we need a sticky or something to say H2 is carrier, it has to be produced just like a battery has to be charged, then we just say that is a given and get on to the practical problem of how best to store and dispatch energy in a world where fossil fuel is unusable or too expensive.

 

[RMForbes]

First of all, I don't want anyone to have an aneurysm. Waste heat from the exhaust is a perfect source for energy recycling. Steam reformers use the heat energy directly to generate hydrogen and convert existing fuels to a cleaner burning more efficient fuel. TEG’s can be used to convert the waste heat energy into electricity. Some of this electrical energy can be used to produce hydrogen and oxygen gas through electrolysis. With millions of internal combustion engines already in use, doesn’t it make more sense to focus on modifying those first, before we create a whole new technology that requires a huge infrastructure that will take several years to develop. Don’t get me wrong, I am not saying we should stop developing hydrogen fuel cells. Just that there are huge gains that can be made much faster by increasing fuel economy on these existing engines while we are producing and developing new technologies.

Yes, hydrogen can be used as an energy storage and transfer mechanism but when injected into an internal combustion engine the combustion characteristics are changed. “Adding small amounts of hydrogen to gasoline produced efficient lean operation by increasing the apparent flame speed and reducing ignition lag” (ref 1977 NASA study). The stored energy of the hydrogen is not the mechanism that is responsible for this increase in efficiency. Hydrogen ignites much easier and burns many times faster than the gasoline or diesel. As it burns it ignites the primary fuel much faster and completely. The resulting combustion starts sooner and burns faster, so all the fuel is consumed long before the end of the power stroke. This is no unburnt fuel to be recycled by the EGR system or incinerated by the catalytic converter. The piston has more time and travel to absorb the energy of the resulting pressure wave and converting this energy into torque. Considerably less energy is lost as heat out the exhaust. By utilizing closed loop control systems and steam fuel reforming systems fuel efficiencies can be optimized by controlling the timing and concentrating full combustion to just a few degrees after top dead center of the power stroke.

 

[Coin]

First of all, I don't anyone to have an aneurysm. Waste heat from the exhaust is a perfect source for energy recycling...

So... this doesn't seem to really be addressing the idea of hydrogen at all? Hydrogen is being proposed as a method of getting energy into car engines, in response you are proposing a generalized method for making car engines more efficient period. While maybe more efficient engines are desirable, surely this is orthogonal to whether the engine is fueled by fossil fuels, hydrogen, or batteries...

Moreover if there is a method for making engines more efficient, I do not think the car companies need any specific extra inducement to use it? Better fuel efficiency is already not only a strong selling point for cars, but mandated by current law and stricter laws to come...

Yes, hydrogen can be used as an energy storage and transfer mechanism but when injected into an internal combustion engine the combustion characteristics are changed. “Adding small amounts of hydrogen to gasoline produced efficient lean operation by increasing the apparent flame speed and reducing ignition lag” (ref 1977 NASA study). The stored energy of the hydrogen is not the mechanism that is responsible for this increase in efficiency. Hydrogen ignites much easier and burns many times faster than the gasoline or diesel. As it burns it ignites the primary fuel much faster and completely. The resulting combustion starts sooner and burns faster, so all the fuel is consumed long before the end of the power stroke. This is no unburnt fuel to be recycled by the EGR system or incinerated by the catalytic converter. The piston has more time and travel to absorb the energy of the resulting pressure wave and converted to torque. Considerably less energy is lost as heat out the exhaust. By utilizing closed loop control systems and steam fuel reforming systems fuel efficiencies can be optimized by controlling the timing and concentrating full combustion to just a few degrees after top dead center of the power stroke.

So I'm not sure I understand what you're suggesting... I think hydrogen is not usually used in an internal combustion engine, my understanding was that hydrogen cars run on fuel cells. I know internal-combustion cars that use hydrogen instead of gasoline have been produced but I think they're mostly gimmicks.

However it sounds like what you're suggesting is a fossil fuel engine that also has a supply of hydrogen, it injects the hydrogen into the fossil fuels it burns, and this increases the performance above and beyond what a fossil fuel or hydrogen engine would be able to achieve on its own? Is this correct? Interesting...

 

[mheslep]

H2 boosting / electrolysis has been debunked on another thread:
https://www.physicsforums.com/showpost.php?p=1830195&postcount=12
https://www.physicsforums.com/showthread.php?p=1830195&highlight=waste#post1830195

 

[russ_watters]

So... this doesn't seem to really be addressing the idea of hydrogen at all? Hydrogen is being proposed as a method of getting energy into car engines, in response you are proposing a generalized method for making car engines more efficient period. While maybe more efficient engines are desirable, surely this is orthogonal to whether the engine is fueled by fossil fuels, hydrogen, or batteries...

Yes, and due to current technological hurdles, hydrogen production is not the most effective way to use that waste heat. Probably the best is an aft-end boiler to drive a turbine.

Of course, the turbine could turn a generator to make hydrogen, but it would probably be better to either connect the tubine to the drive shaft to boost mechanical power or produce energy to be stored in batteries, more like a conventional hybrid.