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Thin film SOFC fuel cells

Discussion in 'Home Power and Microgeneration' started by H. E. Taylor, Jul 24, 2004.

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  1. H. E. Taylor

    H. E. Taylor Guest

    2004/07/22: Eureka: 'Cool' fuel cells could revolutionize Earth's energy resources

    HOUSTON, July 22, 2004 — As temperatures soar this summer, so do electric bills. Researchers at the
    University of Houston are striving toward decreasing those costs with the next revolution in power
    generation.

    Imagine a power source so small, yet so efficient, that it could make cumbersome power plants
    virtually obsolete while lowering your electric bill. A breakthrough in thin film solid oxide fuel
    cells (SOFCs) is currently being refined in labs at the University of Houston, making that dream a
    reality.
    [...]
    Compared to the macroscopic size of traditional fuel cells that can take up an entire room, thin
    film SOFCs are one micron thick – the equivalent of about one-hundredth of a human hair. Putting
    this into perspective, the size equivalent of four sugar cubes would produce 80 watts – more than
    enough to operate a laptop computer, eliminating clunky batteries and giving you hours more juice
    in your laptop. By the same token, approximately two cans' worth of soda would produce more than
    five kilowatts, enough to power a typical household.

    Keeping in mind that one thin film SOFC is just a fraction of the size of a human hair with an
    output of 0.8 to 0.9 Volts, a stack of 100 to 120 of these fuel cells would generate about 100
    volts. When connected to a homeowner's natural gas line, the stack would provide the needed
    electrical energy to run the household at an efficiency of approximately 65 percent. This would be
    a twofold increase over power plants today, as they operate at 30 to 35 percent efficiency.
    [...]
    <http://www.eurekalert.org/pub_releases/2004-07/uoh-fc072204.php>

    <regards>
    -het


    --
    "See that, son?
    That's the moon.
    A long time ago, we used to go there." -stolen .sig

    Name your Poison: http://www.autobahn.mb.ca/~het/catastrophes.html
    H.E. Taylor http://www.autobahn.mb.ca/~het/
     
  2. The interesting thing about SOFC is that their exhaust is mininal but at a
    high temperature: it can make hot water or opperate a turbine for additional
    power or turbo charger to pressurise the cell for higher power densities and
    to generate additional power at higher efficiencies.

    When used at 'home' running on natural gas (or potentialy hydrogen) the
    waste heat can provide home heating and hot water. Thus almost 100% of the
    energy in the natural gas (or hydrogen) will be utalised: some for
    electricity and the rest for home heating.

    Natural Gas and Hydrogen distribution pipelines can also store several days
    worth of gas.

    Such a fuel cell, at 65% efficient, would allow a Hydrogen powered care to
    achieve usable range with a small unburdensome high pressure meatlic gas
    storage cylinder of modest pressure and size. The efficiency means that
    hydrogen made a relatively high cost from renewable energies become
    competitive.

    For instance a 20-25 cubic meter 2800psi-3600psi steel gas cylinder as now
    used on natural gas vehicles and fork lifts contains 1.6kg to 2.0kg of
    hydrogen with an energy content of 50kw.hr to 64.0kw.hr. In a 65%
    efficient cell that is sufficinet to drive a 1 tone vehicle 320km to 400km.
    (consumption 10kwhr/ton/100km)

    If generated by wind (windmill $1/watt and 40% utalisation) and converted to
    hydrogen by alkaline electrolyser (66% efficient and $0.40/watt cost) then
    the hydrogen ends up costing about $0.10 to $0.15 per kw.hr or about
    $10.00 per "tank"!!!

    Ofcourse tax and distribution costs are still there but it is impressive.
     
  3. cyril

    cyril Guest

    Profitant de la d'expression qui, pour quelques semaines encore,
    Not really. The lastest built can exceed 40% for coal-fired units, and
    55% for natural gas (combined cycle).
    I guess the 65% efficiency figure already include some reuse of waste
    heat, in regeneration, using (a) gas/gas exhanger(s) to preheat intake
    air and/or fuel using heat from both electrodes' exhaust gases.

    If so, the rezsidual heat is not available at a very good temperature
    and the gas turbine will have a modest efficiency. But it will reduce
    the size of the needed fuel cell for a given power.
    Right, but that's already true for a microturbine or a reciprocating
    engine with cogeneration. Here, the share of electricity will be
    higfher, so more bucks per cubic feet will be obtained.
    A hybrid car with present or extremely near-term technology could have
    a power plant (diesel engin and generator) that is some 35% efficient.
    65% is a huge leap. However, as hydrogen is not a primary energy
    source, the overall efficiency is lower. Hydrogen could be get from
    fuels (coal, biomass, and so on) with carbon sequestration with some
    70% effiency. 0.7*0.65 = 0.455. Adding energy consomed for H2
    compression, transport and storage will make the figure even lower.
    But the diesel engine also have some upstream energy consumption, like
    the tanker, the oil refinery, and so on.



    If built at a moderate price per kW, SOFCs could help build
    revolutionnary power plants.

    Take a IGCC design like this one :
    http://www.lanl.gov/projects/cctc/factsheets/tampa/images/tampa_schematic_small.jpg


    It is roughly 40% efficient. The main electricity generator is a 35%
    efficient gas turbine.

    Imagine a similar plant with a bunch of SOFCs instead of the gas
    turbine.

    1- Coal is slurried (available technology, for 100 years at least)

    2- It is fed into a oxygen-blown gasifier that convert in into syngas,
    basically a mixture of CO and H2. (available technology)

    3- The syngas is cooled. (available technology, of course)

    4- Pollutants, like sulfur, are removed (available technology).

    5- It is reheated, using a gas/gas echanger with the #3 step
    (available technology).

    6- It is fed into SOFCs (mid-term technolgy). It can burn CO as well
    as H2 (unlike most fuel cells)
    The SOFC's cathode is plugged into a gas turbine that provides
    high-pressure air to it and produce power from expanding its hot
    exhaust air.
    Oxygen is produced using membrane-based air spearation tehcnology
    (near term technology, that will consumes much less power that presend
    cryogenic systems). This Air Separation Unit is also plugged into the
    gas turbine (it takes air from it, and give nitrogen back to it).

    7- The anode's exhaust gases, a mix of CO2 and H2, is sent into a
    boiler and produce steam for a convetionnal steam turbine turbine,
    that also use the heat from the gas turbine and the cooling system of
    the gasifier. Some of the steam is given to the gasifier. (available
    technology, obvioulsy)

    Neary-pure CO2 is produced. So it would be available for
    sequestration. Using sequestration would sacrify a few points in the
    overall efficiency figure but turn our concept into a zero-emission
    plant.




    Gasification is very fuel-flexible. So, in addition to coal, our plant
    may use wastes. Waste are, obviously, inexpensive. some even have a
    negative value, ie people pay you to get rid of them. Here are some
    wastes that could be used :
    - Petcokes, a residuum from oil refineries.
    - Sewage sludge. I was suprised to learn that these sludge have 11 MJ
    per kilogram, meaning that 2-3 pound of them can replace of pound of
    coal.
    - Agricultural wastes, like straw, bagasse, and so on.
    - Blacq liquor from papermills.
    - Wood wastes.
    - municipal solid wastes
    - Any burning industrial waste, even if it is full of pollutants, the
    gasification process will remove them.
    - used tyres.
    - Rush Limbaugh.

    Using partly renewable fuels with sequestration allow "negative CO2
    emissions" : the plant would take carbon from the biosphere and bury
    it.


    Our plant may also produce more than just electricity.
    - Sulfur and heavy metals from syngas cleaning and gasifier ashes can
    be sold, and become valuable assets instead of pollutants.
    - Nitrogen from the ASU may also find some custumers.
    - In cold regions, waste heat from the steam cycle may feed a district
    heating network, espicially since our zero-smoke plant may be built
    closer to urban areas than present-day plants.
    - And, mainly, syngas may be sued to produce chemicals, hydrogen,
    methanol, ethanol, ammonia and so on during low-demand hours for
    electricity. Most of hese products are now obtained from oil and
    natural gas.






    slts
     
  4. This field is a real horse race.
    I read recently of a company in Seattle that is making similar claims.
    In fact, remarkable claims are frequently made, but have not as yet resulted
    in viable products.
    Since this has been going on for ten years or so, I am mildly skeptical.

    I'm not saying that it won't happen, but the technical problems are so
    complex it's difficult or impossible for us nonspecialists to tell from an
    article whether a particular R&D effort is the front-runner, or will
    actually be viable.

    As a sad example, Millenium Cell,
    http://www.millenniumcell.com/about/faq.html, has an interesting technology,
    but the company appears headed for possible bankruptcy, because they were
    unable to convince any manufacturer to invest in the facilities required to
    make the fuel. A good idea, but caught by economics. The founder and
    president of the company recently resigned, possibly in protest of the
    board's intention to dilute the stock.
     
  5. john

    john Guest

    crap
     
  6. Ray

    Ray Guest


    Hmmm...

    I have been wondering about this fuel cell. I have seen lots of
    promises made about various technologies, some of which come to pass,
    and some of which end up going into the trash bin.

    In my research, I'm going to note that John says "crap".

    John, while researching the above claims (to which you answered 'crap'),
    have you found any info that might prove useful? Specifically, I want
    to know if there are any prototypes being tested, and if anyone has
    estimated the date of availability.


    Ray Drouillard
     
  7. I think the article implies there is no actual device.
    As such, it seems to fall into the category of manipulative press releases.
    That said, I certainly do not rule out that this line of research will be
    productive.
    However, there seem to be a lot of manipulative press releases in this area,
    exceeded only by the flurry of claims for cold fusion.
     
  8. Ray

    Ray Guest


    Thank you. I was wondering if that was the case.


    Ray
     
  9. Speaking of which, we're overdue for a "breakthrough in solar cell
    technology", aren't we? It's been nearly a month... 8*)
     
  10. Ray

    Ray Guest

    What happened to the research in organic semiconductors?


    Ray
     
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