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The damage caused by carbon and sulfur buildup is another source of expense. "Nearly every hydrocarbon fuel that's available today contains sulfur, and it's very expensive to take it out," says Michael Day, director of engineering at NexTech Materials, an Ohio company that's developing sulfur-tolerant fuel-cell materials. Filtering impurities from the fuel before it's fed into the cell adds as much as 4 percent to the cost of power generation.
One of the obstacles to improving fuel-cell tolerance has been that researchers are not sure yet what combinations of materials will lead to better performance. Liu stumbled on the poison-tolerant and coking-resistant material while trying to improve the conductivity of the anode. "One day when we tested the cell with a dirty fuel contaminated with hydrogen sulfide, we noticed that the performance didn't change," says Liu. "It has a remarkable tolerance to sulfur, from low levels up to 50 parts per million." Sulfur in the fuel is oxidized and emitted as waste.
The new anode material is a composite of nickel and a ceramic that contains small amounts of two rare-earth metals. Other groups have developed sulfur- and coking-tolerant anodes, but these incorporated expensive materials and degraded cell performance. Replacing the nickel with copper improves a fuel cell's tolerance, but copper isn't as good a catalyst. Coating a conventional anode with ruthenium also prevents sulfur and carbon deposition, but this metal is extremely expensive. And all previously developed anodes, no matter how resistant to coking and poisoning, suffered a performance drop when switched to dirty fuels, says Liu. The Georgia Tech anode, he says, "gives the best performance."
Liu is talking to companies about licensing the anode material. But before it can be brought to market, the new anode will have to be tested over longer periods of time in larger prototypes, he says.
The rest of the world is trying to find alternatives to these crucial materials.
Silicon-nanotube electrodes may enable lithium-ion batteries to store 10 times more charge.
A platinum-free liquid cathode could cut fuel-cell costs by 40 percent.
This is great news and it will be wonderful if they can pull it off .
I would dearly love to see a fuel cell that runs on coal gas .
It is everywhere in China and is carried in bottles that are the same as propane .
Advantages , low cost , clean burning , lots of coal , definitely would be a good substitute for oil .
Hydrogen fuel cells on the other hand are a non starter in my opinion and are just a waste of good research money .
Solid oxide fuel cells represent a terrific, incredibly versatile technology - local to MIT Lilliputian is working on (about to release?)a matchbook size SOFC around 100 watts (and 700C), also Boston area Acumentrics has a 2-3 kW for home combined power and heat, and a U. of Michigan spinoff has an Army trial of 180 watts working. GE and Siemens have failed at coming up with big 1000C MW scale SOFCs for the DOE's clean coal project, but the little guys are doing well. Europe likes SOFC - Ceres in the UK has a 500C 1 kW, but they need hydrogen when the temp is under about 600C, they're no longer self-reforming. And coal is nasty, mining it and gassifying it; its going to take many years and many billions to get right. And it will still be around waiting!
I read about Dairy Farmers in California that are ready to produce and sell back to the grid $100,000 of electricity each month. They are having problem with the EPA because of Nitrogen Oxidides,which are harmful. It seems to me that with SOFCs there would be no NO produced. It would be very nice to see that much renewable energy put to use.
why do you assume there are no nitrous oxides produced?
fuel cells generally use air as a reactant.
air contains 70% nitrogen, which tends to cause nitrogen compounds
Because nitrogen only significantly reacts with oxygen at very high temperatures. It would be extremely low at 500 degrees operating temp.
Also, new end of pipe catalysts have been developed by Argonne that are cheap and very effective at removing NOx emissions from the flue gasses of any powerplant, as well as from diesel engines in cars and trucks.
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JAW
1 Comment
Why large scale?
I'm curious why it is important to achieve large scale? Are the economies that great? Aren't there many potential small scale uses for SOFC?
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yijijuechen
1 Comment
Re: Why large scale?
As for the mobile application, polymer based fuel cell is better since it can start quickly. But SOFC holds several advantages over PEMFC when natural gas can be directly used
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Siphon
152 Comments
Re: Why large scale?
You mean related to reforming?
SOFC probably has to have a strong focus on distributed generation:
- For consumer electronics (miliWatts to Watts) it's a bit impractical with that high operating temperature, even at 500 degrees.
- For mobile applications (kiloWatts), the high operating temperature and heavy shaking/vibrations of moving vehicles are serious issues for durability and practical low cost design.
- For centralized generation (tens to hundreds of MegaWatts), it has to compete with advanced combined cycles which are about as efficient and clean but probably cheaper for a long time to come.
But, for decentralized generation, it's great with it's modularity (hundreds of Watts to kiloWatts all at high fuel efficiency) and few moving parts (only the compressor/fuel pumps?)
They could start with the off grid diesel generator market. Diesel delivered to remote areas is expensive so fuel efficiency really counts. Probably the best $$$ market right now.
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