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Fuel cells versus Batteries

  1. Mar 15, 2009 #1
    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 ......
     
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  3. Mar 15, 2009 #2

    Pythagorean

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    batteries are most economic, currently. I'm looking forward to more R&D in all kinds of alternatives to fossil fuels though.
     
  4. Mar 15, 2009 #3
    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?
     
  5. Mar 15, 2009 #4

    Ivan Seeking

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    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.

    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.

    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.
     
    Last edited: Mar 15, 2009
  6. Mar 15, 2009 #5
    My opinion may be somewhat biased as my research area is fuel cells, but I believe I is still well informed about both technologies.

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

    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.

    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.

    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]

    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.

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

    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.
     
    Last edited: Mar 15, 2009
  7. Mar 15, 2009 #6

    russ_watters

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    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.
     
  8. Mar 15, 2009 #7

    Ivan Seeking

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    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.
     
  9. Mar 15, 2009 #8

    Ivan Seeking

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    For general information:
    http://www.hydrogenassociation.org/general/factSheets.asp [Broken]
    http://www.hydrogenassociation.org/general/index.asp [Broken]
     
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  10. Mar 15, 2009 #9

    russ_watters

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    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.
    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 not a fuel, it is an energy storage medium.
    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.
    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.
    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.
     
  11. Mar 15, 2009 #10

    russ_watters

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    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.
     
  12. Mar 15, 2009 #11
    Fuel, a flywheel, a head of water, a battery are all energy storage mediums.
     
  13. Mar 15, 2009 #12

    russ_watters

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    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 [Broken]
    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:
    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:
     
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  14. Mar 15, 2009 #13

    Ivan Seeking

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    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.
     
  15. Mar 15, 2009 #14

    Ivan Seeking

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

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

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

    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.

    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.

    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.
     
    Last edited: Mar 15, 2009
  16. Mar 15, 2009 #15
    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.


    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.

    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.

    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/

    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.

    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.

    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.
     
    Last edited: Mar 15, 2009
  17. Mar 15, 2009 #16
    I surely must be speaking a foreign language if I can say one thing and it's heard as another.
     
  18. Mar 16, 2009 #17
    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.
     
  19. Mar 16, 2009 #18
    Methane, you mean.

    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.
     
  20. Mar 16, 2009 #19
    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.

    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.
     
    Last edited: Mar 16, 2009
  21. Mar 16, 2009 #20
    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?
     
    Last edited: Mar 16, 2009
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