Fuel cells versus Batteries

[Oxygenne]

batteries or fuel cells?

hydrogen costs too much to be an effective fuel alternative?
the catalyst required for the electrochemical conversion reaction is pricey platinum?
Using hydrocarbons as a source for hydrogen we have more CO2 in the atmosphere?
and require a high temperature reactor under the car seats?

I just do not see if the fuel cells have a real future or ...

 

[Pythagorean]

batteries are most economic, currently. I'm looking forward to more R&D in all kinds of alternatives to fossil fuels though.

 

[Phrak]

What possible advantage is there in using hydrogen as an energy storage product, when it is derived from hydrocarbons? About none, I'd think. Even in the global-warming-carbon-footprint camps it shouldn't make too much sense.

It is used in places to replace the diesel fume spewing in mass transits, but what measure is this?

 

[Ivan Seeking]

What possible advantage is there in using hydrogen as an energy storage product, when it is derived from hydrocarbons?

Hydrogen is an energy storage medium that can be produced using excess energy. Energy storage has always been a problem for traditional and alternative energy technolgies. For example, Iceland has tremendous reserves of geothermal energy. They hope to use this to produce hydrogen, which could then be used or sold as a fuel. Likewise, it can be produced using wind, solar, hydro, nuclear, or any form of electrical power, and water or hydrocarbons. It may also be produced directly through biological processes. Right now there is a team at MIT working to produce hydrogen using algae.

Hydrogen is the ultimate clean fuel. Anyone who grew up in a city can appreciate the value of having nothing but water as exhaust fumes.

About none, I'd think. Even in the global-warming-carbon-footprint camps it shouldn't make too much sense.

Assuming that all practical aspects of hydrogen production and transportation are addressed, it makes exactly as much sense as the total of internal combustion emissions. You are effectively arguing that internal combustions play no significant role in CO2 emissions. But CO2 aside, it is the only completely clean fuel for combustion.

It is used in places to replace the diesel fume spewing in mass transits, but what measure is this?

See the cost of health care as a function of air pollution. It is huge! Things have improved some, but when I was a kid living in Los Angeles, it was found that other kids living in the most air-polluted areas of Los Angeles had the lungs of a pack-a-day smoker. Did you watch the olympics in China this summer? It was almost too dangerous to compete due to the levels of air pollution.

Hydrogen over fuel cells is the most efficient configuration for automotive applications if we have a source of hydrogen. But from where I sit, fuel cells are far too expensive to be practical for [standard] personal vehicles any time soon. I tend to favor hydrogen for internal combustion. While this is far less efficient than hydrogen/fuel cell/ electric, traditional internal combustion engines can easily be modified to burn hydrogen without any significant loss of performance. It could also play a role where electric motors are not an option, such as in heavy industry, aviation, and the shipping industry.

 

[Topher925]

My opinion may be somewhat biased as my research area is fuel cells, but I believe I is still well informed about both technologies.

hydrogen costs too much to be an effective fuel alternative?

False. Hydrogen's problem are in its method of storage, not the cost of the fuel itself.

the catalyst required for the electrochemical conversion reaction is pricey platinum?

Your average catalytic converter contains a lot more platinum that your fuel cell stack of equivalent power. Yes platinum is expensive, but compared to other chemicals such as lithium, the cost of it isn't an issue.

Using hydrocarbons as a source for hydrogen we have more CO2 in the atmosphere?

Not necessarily. One method of deriving H2 is by reforming hydrocarbons such as methanol. However, there are numerous ways to generate H2 with no CO2 generation in any part of the cycle. For example, solar thermolysis.

and require a high temperature reactor under the car seats?

Why would you have a reactor, let alone one under your seat? If a vehicle uses a liquid hydride it will have a reactor but it won't be located under the seat of the car. [/QUOTE]

I just do not see if the fuel cells have a real future or ...

PEM fuel cells are the slated to be the #1 technology to replace thermal engines and for good reason. Studies have shown the economics of fuel cell technology is cheaper than that of batteries, which is why all major auto manufacturers developing all fuel cell powered cars and not all electric cars. For example, the Honda FCX Clarity.

batteries are most economic, currently. I'm looking forward to more R&D in all kinds of alternatives to fossil fuels though.

Currently, yes. Although a hydrogen infrastructure does not currently exist so it can be difficult to compare.

What possible advantage is there in using hydrogen as an energy storage product, when it is derived from hydrocarbons? About none, I'd think. Even in the global-warming-carbon-footprint camps it shouldn't make too much sense.

There is some. Electrochemical engines are about twice as efficient as comparable thermomechanical engines and as a result can produce less CO2.

Fuel cells by their very nature offer features that batteries can not. The obvious one is no need for recharging, longer life span, and much less to none of an environmental impact when being disposed of. Other advantages are greater power to weight ratios and no self discharging.

 

[russ_watters]

What possible advantage is there in using hydrogen as an energy storage product, when it is derived from hydrocarbons? About none, I'd think. Even in the global-warming-carbon-footprint camps it shouldn't make too much sense.

It is used in places to replace the diesel fume spewing in mass transits, but what measure is this?

It would only be useful as a storage medium similar to batteries and derived from water. For that purpose, its main benefit is that is has a much higher energy density than a battery.

 

[Ivan Seeking]

False. Hydrogen's problem are in its method of storage, not the cost of the fuel itself.

What is the price of a Kg of hydrogen? Also, we don't have an energy competitive means of producing hydrogen. The well-to-wheels efficiency of a process is what ultimately matters.

 

[Ivan Seeking]

For general information:
http://www.hydrogenassociation.org/general/factSheets.asp
http://www.hydrogenassociation.org/general/index.asp

 

[russ_watters]

Hydrogen is an energy storage medium that can be produced using excess energy. Energy storage has always been a problem for traditional and alternative energy technolgies. For example, Iceland has tremendous reserves of geothermal energy. They hope to use this to produce hydrogen, which could then be used or sold as a fuel.

Iceland is a completely unique situation that provides no insight whatsoever into the issue anywhere else in the world. It is completely irrelvant here. In the rest of the world, there is no such thing as "excess energy" in the context you are using it. Ie:

Likewise, it can be produced using wind, solar, hydro, nuclear, or any form of electrical power, and water or hydrocarbons.

None of those are "excess energy" and will not be for the forseeable future. Not until they replace half of our current generating capacity.

It may also be produced directly through biological processes. Right now there is a team at MIT working to produce hydrogen using algae.

That's true, but it is a bit like fusion: it is 30 years away from being ready for commercialization and in 30 years, it probably still will be.

Hydrogen is the ultimate clean fuel.

Hydrogen is not a fuel, it is an energy storage medium.

Anyone who grew up in a city can appreciate the value of having nothing but water as exhaust fumes.

Since hydrogen isn't a fuel, that's just a misdirection hydrogen advocates throw around. In the world we live in today, hydrogen made by electrolysis exhausts carbon dioxide and lots of it.

Hydrogen over fuel cells is the most efficient configuration for automotive applications if we have a source of hydrogen.

Translation: if we ignore it's inefficiencies, hydrogen is efficient! That's just an absurd thing to say, Ivan. The reality of the issue is that hydrogen is not an efficient energy storage medium because producing it is a very inefficient process. Something like half the efficiency of batteries when used in a fuel cell.

But from where I sit, fuel cells are far too expensive to be practical for [standard] personal vehicles any time soon. I tend to favor hydrogen for internal combustion. While this is far less efficient than hydrogen/fuel cell/ electric, traditional internal combustion engines can easily be modified to burn hydrogen without any significant loss of performance.

That's a terrible idea. Starting with an energy storage medium that's half as efficient as batteries and ending with a usage that cuts the efficiency by an additional factor of 3. Now you have a car that operates at 1/6 the efficiency of a battery operated electric car. That's a big step backwards.

 

[russ_watters]

What possible advantage is there in using hydrogen as an energy storage product, when it is derived from hydrocarbons? About none, I'd think.

When derived from hydrocarbons, you can consider hydrogen a "fuel", not just an energy storage medium. The conversion is a refinement process not unlike how oil from an oil well is converted to gas in your car.

Traditionally, the refinement process simply releases the CO2 that burning the fuel for fuel would, so for now you are right - the pollution result is roughly the same. However, if carbon sequestering technology ever becomes a reality, then refining might be a viable option. I won't hold my breath for it any time in the near future, though.

 

[Phrak]

Fuel, a flywheel, a head of water, a battery are all energy storage mediums.

 

[russ_watters]

PEM fuel cells are the slated to be the #1 technology to replace thermal engines and for good reason. Studies have shown the economics of fuel cell technology is cheaper than that of batteries, which is why all major auto manufacturers developing all fuel cell powered cars and not electric cars. For example, the Honda FCX Clarity.

Currently, yes. Although a hydrogen infrastructure does not currently exist so it can be difficult to compare.

In light of the last sentence, I'd like to see some justification for the first. I'd like to see those studies. The last sentence implies to me that your statement is based on ignoring the cost of the infrastructure.

Also, the statement that electric cars are not being developed is just plain false. The worst that can be said about plug-in hybrids is that they are electric cars with an ICE backup. For people who would buy them, an extremely high fraction of their driving will be electric only, acting as a pure electric car.

Car companies are also, in fact, racing to develop production electric cars. Here's a statement of intent from VW: http://www.cleanedge.com/news/story.php?nID=5914
Mercedes says they will be on the road in 2011: http://www.usatoday.com/money/autos/environment/2008-03-23-mercedes-electric-car-battery_N.htm

Ford, too: http://blogs.cars.com/kickingtires/2009/01/ford-electric-car.html

Are any car companies actually planning on making production fuel cell cars, as opposed to technology demonstrators not ever meant to be sold? I don't think so. Here's what Ford says:

Ford researchers agree that much more work needs to be done before fuel cell vehicles can be commercialized. The biggest challenge according to Rob Riley, Ford fleet manager in California, is building a viable H2 infrastructure with fueling stations across the country.

http://www.autobloggreen.com/2008/08/19/ford-expands-fuel-cell-test-fleet-tests-by-two-years/
And that's even before you begin to address the commercial viability of the cars themselves:

Customer surveys suggest purchase consideration also will be dictated by affordability, reliability and useful life of the vehicle, as well as availability of fueling stations. In addition, parts availability and an adequate number of trained technicians will be essential to ensure convenient customer service of the vehicles.

 

[Ivan Seeking]

Fuel, a flywheel, a head of water, a battery are all energy storage mediums.

We do use uphill pumping for water energy storage, but that is only practical in some cases. It also tends to waste a lot of water through evaporation and seepage. Water shortages are an issue in many areas of the US other countries.

We can't make other fuels as easily as we can H2.

Batteries have always been impractical in terms of energy storage, but people are working hard to solve that problem. However, at this time we have no reason to believe that batteries will ever be practical for anything except [short distance] commuter vehicles.

Flywheel technology has been around a long time and enjoys a very limited market. In fact I investigated flywheel energy storage for a real application recently [for my job] and found it to be far too limited and too expensive to be useful. For one, the flywheel units cannot tolerate vibrations.

 

[Ivan Seeking]

Iceland is a completely unique situation that provides no insight whatsoever into the issue anywhere else in the world. It is completely irrelvant here. In the rest of the world, there is no such thing as "excess energy" in the context you are using it. Ie: None of those are "excess energy" and will not be for the forseeable future. Not until they replace half of our current generating capacity.

Iceland is unique. However, the point was that H2 can be used as a storage medium.

That's true, but it is a bit like fusion: it is 30 years away from being ready for commercialization and in 30 years, it probably still will be.

Did you get that from your psychic? How much time have you spend studying the subject; none?

Hydrogen is not a fuel, it is an energy storage medium.

When derived from hydrocarbons, you can consider hydrogen a "fuel", not just an energy storage medium

If is a fuel, but unless taken from existing HC, it is not a source of energy.

Since hydrogen isn't a fuel [it is a fuel] that's just a misdirection hydrogen advocates throw around. In the world we live in today, hydrogen made by electrolysis exhausts carbon dioxide and lots of it.

Hydrogen does not exhaust CO2. That is a blatently false statement and you know it. And obviously the point would be to produce the hydrogen using clean technologies. No one said it is a viable option today.

Translation: if we ignore it's inefficiencies, hydrogen is efficient! That's just an absurd thing to say, Ivan. The reality of the issue is that hydrogen is not an efficient energy storage medium because producing it is a very inefficient process.

Get a grip. I said that earlier myself. I limited my statement in this case to the assumption that we already have the hydrogen. Now try to pay attention.

Something like half the efficiency of batteries when used in a fuel cell. That's a terrible idea. Starting with an energy storage medium that's half as efficient as batteries and ending with a usage that cuts the efficiency by an additional factor of 3. Now you have a car that operates at 1/6 the efficiency of a battery operated electric car. That's a big step backwards.

If we consider lifetime efficiency of the car [and all required technology], it may make sense if we have a good source of hydrogen. What's more, electric is not always an option, such as for trucks. Also, the grid could not sustain a nation of electric vehicles and may not be able to for many decades to come.

 

[Topher925]

What is the price of a Kg of hydrogen?

I don't know what the bottom dollar price is but we pay about $1.95 per kg of H2 for our FC testing lab at school.

Hydrogen is not a fuel, it is an energy storage medium.

Incorrect. Hydrogen is a fuel, hence the name "Fuel Cell". Definition of a fuel: "an energy source for engines, power plants, or reactors". Hydrogen is as much a fuel as gasoline and diesel, the only difference is that we are breaking and recombining the chemical bonds and not nature.

That's true, but it is a bit like fusion: it is 30 years away from being ready for commercialization and in 30 years, it probably still will be.

How do you know? Are you a biochemist at MIT who does research in biofuels? Fusion is an entirely different ball game and is no where near as simple as breaking down organic matter with a H2 byproduct.

In light of the last sentence, I'd like to see some justification for the first.

I did have a good study done on this from an 08 fuel cell convention but I think its on my PC at school. In the mean time there are plenty of good articles on line such as this one: http://www.autobloggreen.com/2009/0...n-proponent-sandy-thomas-says-fuel-cells-bea/

Are any car companies actually planning on making production fuel cell cars, as opposed to technology demonstrators not ever meant to be sold? I don't think so. Here's what Ford says:

First of all, who cares what Ford says they haven't done anything in terms of fuel cell development. Second, what do you think the purpose of the FCX Clarity is? Honda isn't going to spend millions of dollars and lease out hundreds of FC cars for nothing. Both Honda, Toyota, and GM are performing major research in the area of PEM fuel cells as they are expecting it to be the future power plant of transportation.

Also, the statement that electric cars are not being developed is just plain false.

What major auto manufacturers are developing all electric vehicles that are planned to compete with gasoline powered vehicles and not a glorified gokart for city driving? The ICE in series hybrids are not a "back up" at all. They are there to actually power the vehicle past its very short 40 mile battery capacity.

Hydrogen does not exhaust CO2. That is a blatantly false statement and you know it.

Hell yeah it is. As a matter of fact methods of hydrogen production have greatly advanced in the past few years becoming more efficient, less expensive, and in most cases generate no pollution for the generation process itself.

 

[Phrak]

We do use uphill pumping for water energy storage, but that is only practical in some cases. It also tends to waste a lot of water through evaporation and seepage. Water shortages are an issue in many areas of the US other countries.

I surely must be speaking a foreign language if I can say one thing and it's heard as another.

 

[signerror]

What possible advantage is there in using hydrogen as an energy storage product, when it is derived from hydrocarbons?

It is presently derived from natural gas, and the demand (for hydrocarbon cracking) is low enough that this is viable. There is no technical reason why this is necessary - it can be made from splitting water, for instance. I strongly doubt that natural-gas derived hydrogen would be used for fuel on a large scale - that would be obviously inferior to powering cars directly from CNG, cutting out the transformations in the middle.

 

[signerror]

Not necessarily. One method of deriving H2 is by reforming hydrocarbons such as methanol.

Methane, you mean.

However, there are numerous ways to generate H2 with no CO2 generation in any part of the cycle. For example, solar thermolysis.

That's a bit restrictive. ANY energy source can be used to split water - every clean energy source, from hydropower to nuclear. And thermolysis is only particular method (a bit extreme, isn't it?); alternate approaches are electrolysis (redox reactions driven by an applied voltage) and thermochemistry (chemical transformations running off of an applied temperature difference - basically chemical heat engines). An example of the latter is

http://en.wikipedia.org/wiki/Sulfur-iodine_cycle

I think the temperatures involved (~800 °C) are much more manageable than direct thermolysis of steam.

 

[signerror]

What is the price of a Kg of hydrogen?

I don't think it is meaningful, because there is no hydrogen fuel economy, so current prices do not reflect what commercial fuel would cost.

Also, we don't have an energy competitive means of producing hydrogen. The well-to-wheels efficiency of a process is what ultimately matters.

I disagree; it's the total cost which matters. Given very cheap energy sources, a highly wasteful hydrogen economy (say liquid hydrogen combusted in a pure oxygen environment (very clean)) could be superior to, say, efficient EVs with extremely expensive batteries. This of course is assuming a hydrogen combustion engine, which would be very cheap, rather than a fuel cell stack.

But with expensive energy, the advantages would be reversed.

 

[Phrak]

Hydrogen is not an energy source. Hydrogen is a way to store energy that comes at a hefty premium. Dynamite is a way to store energy, and probably a bit safer. Where is the 'dynamite as fuel' advocacy thread?

 

[Phrak]

Hydrogen from electrolysis runs at a dismal 40% efficiency. Stored in liquid from it evaportes to keep the rest below boiling point. There is unrecoverable energy spent in compressing it.
How does this make more sense than powering a car with water?


With dwindling supplied of crude, the first consideration is the source of energy, not it's storage medium.

 

[Zdenka]

An advanced civilization would be laughing their heads off that our society is still running on the fats of dead beasts from long ago.

 

[Topher925]

Methane, you mean.

No, I meant methanol. http://en.wikipedia.org/wiki/Methanol_reformer

That's a bit restrictive. ANY energy source can be used to split water - every clean energy source, from hydropower to nuclear. And thermolysis is only particular method (a bit extreme, isn't it?);

Yes, thermolysis is a rather extreme example but it offers a great benefit that other methods of H2 generation can not. Thermolysis has the capability of directly creating H2 from sun light extremely efficiently. Although current thermolysis reactors only operate at ~2% efficiency the technology is promising.

Hydrogen is not an energy source. Hydrogen is a way to store energy that comes at a hefty premium.

Technically, neither is gasoline. What's your point? I wouldn't call the premium's "hefty". There are more ways of storing hydrogen then compressing it and freezing it to liquid form.

Hydrogen from electrolysis runs at a dismal 40% efficiency.

If it was 1975, you might be right. Most modern electrolysis setups are around 65%, some at 80%. And let's not forget about the recent work by MIT.
https://www.physicsforums.com/showthread.php?t=248265
http://www.qsinano.com/white_papers/2006_09_15.pdf

How does this make more sense than powering a car with water?

How do you power a car with water?

 

[Phrak]

No, I meant methanol. http://en.wikipedia.org/wiki/Methanol_reformer

If it was 1975, you might be right. Most modern electrolysis setups are around 65%, some at 80%. And let's not forget about the recent work by MIT.
https://www.physicsforums.com/showthread.php?t=248265
http://www.qsinano.com/white_papers/2006_09_15.pdf

How do you power a car with water?

The supplied links hardly make your point. Where does the electrical power come from. Are you going to burn Hydrogen to get it? There is something of the practicle missing.

 

[mheslep]

Hydrogen is not an energy source. Hydrogen is a way to store energy that comes at a hefty premium. Dynamite is a way to store energy, and probably a bit safer.

Hydrogen, like gasoline, requires safety measures but it is not an explosive boogey man.

https://www.physicsforums.com/showpost.php?p=1789430&postcount=97

 

[Phrak]

Hydrogen, like gasoline, requires safety measures but it is not an explosive boogey man.

https://www.physicsforums.com/showpost.php?p=1789430&postcount=97

ok... I doubt storing hydrogen in a big bag under atmospheric pressure in the trunk is a viable means in the use hydrogen as a transportation fuel. The alternatives are pressurization+cooling or pressurization+evaporation cooling or stored as a hydride. I don't recall gasoline requiring this added attention.

If hydrogen as transportation fuel is more than yet another empty promise, I'm sure the advocates are aware of the production and supply chain economics, the means of generation, storage, and distribution, the comparison of costs to gasoline, diesel, and electric vehicle power, and the BTU per dollar comparison. I'm all ears.

 

[Topher925]

The supplied links hardly make your point.

I'm sorry, but how does five different methods of electrolysis with production efficiencies greater than 40% not prove my point? Did you even read the links?

Where does the electrical power come from.

Any electrical source you want. Solar, wind, hydro, nuclear, take your pick.

Are you going to burn Hydrogen to get it?

Why would you burn hydrogen to generate hydrogen? You're not making any sense.

There is something of the practicle missing.

Your understanding of what electrolysis actually is?

I don't recall gasoline requiring this added attention.

I don't recall gasoline being pollution free and having the greatest energy density than any other chemical fuel.

If hydrogen as transportation fuel is more than yet another empty promise, I'm sure the advocates are aware of the production and supply chain economics, the means of generation, storage, and distribution, the comparison of costs to gasoline, diesel, and electric vehicle power, and the BTU per dollar comparison.

Are you aware of these things? The cost to fuel the Honda FCX (~70mpkg of H2) is about the same it takes to fuel my Honda Civic (~34mpg) assuming you buy your H2 in California ($5/kg) and with current gas prices in MI of $2 a gallon. If you want to compare numbers from 6 months ago when gas was $4+ a gallon, its pretty obvious that H2 is a hell of a lot cheaper.

H2 in most other states such as Illinois, it is actually much cheaper and can be found around $3.50 per kg. In Dearborn, MI near where I used to work, I believe you could buy a gallon of H2 for your FC car for around $3.70/kg.

http://www.hydrogencarsnow.com/blog2/index.php/hydrogen-distribution/illinois-opens-first-hydrogen-fueling-station-today/

And all of this is WITHOUT a hydrogen infrastructure!


Global Hydrogen Link Removed. I'll repost it later if I can confirm it is legit.

 

[mheslep]

You also have companies such as Global Hydrogen which can produce H2 for even cheaper than that, around $2.60/kg

http://www.newswiretoday.com/news/37455/

And all of this is WITHOUT a hydrogen infrastructure!

I'm skeptical that the GH price accounts for any infrastructure at all. That is, I suspect their price accounts only for the energy cost of making the H2, not the annualized capital cost of installing the electrical infrastructure (4-5MW), nor the water supply infrastructure (2000gal/day), not to mention the cost of the onsite H2 storage and electrolysis equipment itself, that a comparable vehicle H2 refueling station would require.

 

[Phrak]

I'm will await for the worldly responses that are more than empty promises based on a laboratory demonstration and the like. In the real world, dreams don't come true because it's way cool. You need to put in more than 10%.

Just for starters, 1) How do I store 12 gallons of liquid hydrogen in a vehicle? (Liquid hydrogen has about 1/2 the BTU content of gasoline.)

 

[signerror]

How do I store 12 gallons of liquid hydrogen in a vehicle?

Like this.

http://www.wired.com/news/images/full/hydrogenbmw2_f.jpg

One major challenge is how to keep the hydrogen cooled to minus 253 degrees Celsius (minus 423 degrees Fahrenheit) so it remains in liquid form without boiling off. Despite the double-walled, stainless-steel tank [a Dewar flask] that stores the liquid in high-vacuum conditions with aluminum reflective foil [which reflects infrared, to slow the rate of radiative heat transfer], the liquid hydrogen in the 8-kilogram fuel tank begins to boil after 17 hours if the car remains parked. The tank empties completely after 10 to 12 days.

During the test drive, I pulled over to a Total hydrogen filling station to tank up.

The BMW Hydrogen 7 holds approximately 8 kilograms of liquid hydrogen. The car consumes about 15 miles per kilogram for a total cruising range of 120 miles, BMW says. In gas mode, the car's 74-liter (19.5-gallon) gasoline tank offers a range of about 300 miles.

http://www.wired.com/cars/energy/news/2006/11/72100?currentPage=all

 

[signerror]

http://img301.imageshack.us/img301/857/800pxwasserstoffeinfc3b.jpg

 

[mgb_phys]

Also from the same company as the BMW system.
Uses H2 fuel cells instead of batteries and regenerates H2/O2 at sea from diesels .

 

[mheslep]

Also see previous threads
https://www.physicsforums.com/showthread.php?t=276757&referrerid=70823"
https://www.physicsforums.com/showthread.php?t=204457&referrerid=70823"
and
http://www.rsc.org/images/NEWS-p14-395_tcm18-99997.jpg

 

[mheslep]

(Liquid hydrogen has about 1/2 the BTU content of gasoline.)

Yes and no. Liquid H2 has a 3x greater energy density by weight (143MJ/kg) than gasoline (47MJ/kg), but a 1/3 lower volumetric density (10 MJ/L vs 34MJ/L). Typically the addition of an impact resistant cryogenic tank eats away the weight advantage. Of course if a spacecraft is the goal, where a weight is mostly the only concern then one can't beat liquid H2 for a fuel / energy carrier / whatever.

 

[Phrak]

Take out the back seat, and install a tank good for a 120 mile range. That's 1% of a compromise dsolution.

That tank wouldn't fit in the 'skateboard' chassis so excitedly promoted on the Planet Green channel. Why is that? But, then again, they were talking about perpetual motion automobiles last Sunday.