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1. Solid oxide fuel cells operate at very high temperatures—-around 1,000°C (1,830°F). High temperature operation removes the need for precious-metal catalyst, thereby reducing cost.
2. Stirling engines are the most efficient engines; they work on thermal differences; the higher the temperature difference
between the hot point and the cold point, the more efficient the stirling works.
3. Now couple both: the fuel cell produces primary electricity to drive the electric motor; but in ordinary fuel cells for cars, the waste heat is often not used efficiently: now use this heat as the hot pole for the stirling; 1000°C is super okay! The stirling operates as a generator delivering electricity to a battery; for acceleration, the central motor draws extra electricity from this battery.
4. Could be extremely efficient!!!
Electricity from fuel-cell waste heat
http://americanhist...uelcells/basics.htm
No method suggested. Scroll down to 'molten carbonate fuel cells'. [spidermother, Feb 24 2006]
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Annotation:
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Could be, if you describe exactly how you plan to reach 1000°C. What is the fuel? |
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Interesting. And, your fluid that's moving around in the stirling engine would need to withstand 1000 C too. (And, the components of the stirling engine too....) |
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Most things that withstand 1000C are brittle ceramics, so it may be more suited to stationary power rather than mobile. |
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Heat doesn't focus unless it's radiative. Focusing heat violates entropy laws. So, it's a hard sell to take waste heat from a low temperature source and bring it up to 1000C. |
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/Stirling engines are the most efficient engines/ |
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I choked on my celery stick when I read that. |
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]]I choked on my celery stick when I read that.[[
Which engine do you see as more efficient then? |
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[sophocles], you're right about the extreme heat, but that shouldn't be a problem: many stirling engines withstand heat of up to 800°c.
For example, the solar dish stirlings take 800°c. You just channel the heat up to a point where it becomes manageable by the engine. You don't need to make the entire engine out of ceramics. |
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Moreover, the idea could work with lower temperature fuel cells as well (there's a whole range, with fuel cells operating at 50°c all the way up to 1200°c -- have your pick! :-) |
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The idea's more about simply using the waste heat off of a fuel cell to couple it to an efficient stirling. |
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[RaoyfordSteele], I'm not an expert in fuel cells, but the one I was looking at works on hydrogen. I imagine that the 1000°c which are mentioned for this type of fuel cell (solide oxide) is very concentrated at a few points (dunno); when you channel that heat to the stirling, you might have lost a certain amount.
Moreover, the idea could work with fuel cells that operate on lower temperatures. |
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Re: efficiency, I now concede that the statement is correct. |
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I'll leave my anno there as a beacon of my ignorance. |
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The higher the temperature the more useful energy the Stirling engine can extract from the waste heat, as [django] implies. |
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I've found only one reference to generating extra electricity from fuel-cell waste heat (link), with no specific method suggested, so it doesn't seem baked. |
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Fuel cells that use hydrocarbons, alcohols etc. extract no electrical energy from the carbon, which produces only waste heat. That's where this could come in. |
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//Mega-efficient//: hyperbole? I would have written 'more efficient'. (+) |
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