h a l f b a k e r yA riddle wrapped in a mystery inside a rich, flaky crust
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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]
[link]
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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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By using a thermoacoustic Stirling engine, one can put the "moving parts," such as they are, at the cold end of the engine. The working fluid could be hydrogen, which of course wouldn't break down. |
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Now there's a statement worthy of a tagline: |
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"I'll leave my anno there as a beacon of my ignorance" |
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A poster after my own heart. |
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