Heat from auto rad and exhaust in to elctricity thru Stirling.

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Response to Heat from auto rad and exhaust in to elctricity thru Stirling.

Postby lwatcdr » Wed Nov 14, 2007 8:24 am

I have been thinking about the same thing but I don't think that a Stirling engine is the best way.
There is already a proven technology to recover waste heat from car exhaust. Wny not use a turbine? Turbochargers have been used for years. Just remove the compressor and add a small generator. Add that to a hybrid and I would wonder how much extra mileage you would get.
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Response to Heat from auto rad and exhaust in to elctricity thru Stirling.

Postby hengsteler08 » Fri May 09, 2008 5:31 am

I have to disagree with Mr. Hornbaker in assessment of the amount of waste energy (heat), and the delta-T. If you drive your average 4-cylinder car at dusk for 20 miles at 65 MPH then pull over, pop the hood, and look at the exhaust manifold, I bet you'll see it glowing a dull red or brighter. This corisponds to a temperature of about 900F. Mind you, this temperature was obtained while a huge amount of air flow was going through the engine compartment constantly cooling the exhaust manifold. If the manifold were shielded from air flow cooling, I'd be willing to bet a cookie that temperatures of 1200F+ would not be out of the question. If ambient air were ducted to the "cooling" side of a Stirling engine, a delta-T of 1100F is not out of reason. This heat could be used for Stirling or micro-turbine electric power generation. What to do with the extra electricity? For one, you could run ALL the items that suck power from the cars engine: water pump, power steering pump, a/c compressor, not to mention all the electronics, lights, fans, cd's, tv's, and may have some power left to put back into the engine's crankshaft. (I would love to see this coupled with the emerging "Brown's Gas" technology!)
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Postby dplconsulting » Fri May 09, 2008 7:26 am

Mr. Hengsteller is 100% right on the money. As new sources of energy become harder or more expensive to develop, recovering waste engergy becomes increasingly more attractive from environmental, economic and security of supply perspectives.
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Response to Heat from auto rad and exhaust in to elctricity thru Stirling.

Postby bptdude___2569 » Fri May 09, 2008 8:40 am

Mr. Hornbaker is just trying to convey some dash of reality gleened by so many over so long a time. I think the world of Stirling engines myself, and given spare time and resources would probably have a lot of fun creating workable machines.

Extracting heat from the tailpipe, just is not going to generate that much usable energy in terms of watts. If you could build one, you are talking about enough juice to power electronics, not juice up the main batteries for a hybrid.

A mechanical Stirling to create enough power would be too bulky, size and weight and too much machinery. You would have a car with two engines.

If I had to solve this, I would approach it with an acoustic design. The heat creating high pressure sound waves, a novel new type of Stirling. This would allow for a small, light design with few moving parts, built lengthwise along the exhaust. The tricky part would be engineering not the acoustic Stirling, actually, but converting the high pressure sound waves into electricity. That would be my big value added design.

This might work.

Mr. Hornbaker?

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Response to Heat from auto rad and exhaust in to elctricity thru Stirling.

Postby dplconsulting » Fri May 09, 2008 8:56 am

For the record, we both know Mr. Hengsteler was not talking about collecting energy at the tailpipe, but at the header where the majority of the energy being consumed by an internal combustion engine is being wasted.

A heat to ultrasonic converter might be an interesting beast, but it certainly wouldn't qualify as a Stirling. Perhaps there's a new forum in the making....?
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Postby bptdude___2569 » Fri May 09, 2008 10:55 am


tailpipes / headers, trivial difference.
if you were going to build this, you would replacing the entire exhaust system anyway.

you should do your homework about Stirling engines, too. There does indeed a class of Stirlings known as thermoaucoustic. I did not make that up.

This idea is very practical.. but who do I tell. I came up with a way to make a variation of this work...

An expensive fancy Stirling exhaust system could indeed power something important in a car, saving fuel, and an even fancier version provide a way cool luxury.

:)

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Response to Heat from auto rad and exhaust in to elctricity thru Stirling.

Postby dplconsulting » Sat May 10, 2008 10:07 am

The temperature difference the header, or exhaust manifold as it is called, and the tailpipe is close to 1,000 degrees. That's not a trivial amount, especially when the success of a Stirling engine is proportional to the temperature differential.

Not recoginizing the difference between these points could explai the lack of appreciation for using a Stirling engine for waste heat recovery.

According to the most recent reports, acoustic to electric energy conversion is still a laboratory curiosity not consistent with the classic definition of a Stirling. By comparison, thermopiles are considerably further down the track in terms of practical application.

Meanwhile, Stirling engines have been built small enough to recover waste heat from a microprocessor chips and large enough to from the basis of a huge new solar farm being built in the US Southwest.

Why not explore the potential for optimizing Stirling technology for auto exhaust waste heat recovery? We would be foolish not to.



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Response to Heat from auto rad and exhaust in to elctricity thru Stirling.

Postby bptdude___2569 » Sat May 10, 2008 6:21 pm

Hi Dale,

I do not want to pick a blog fight with you. This is a nice place.

Headers versus tailpipe has a heat difference, and meaningful if you want to kludge a cool homebrew gadget. I was talking an engineered system, which would think out how to handle engine heat output from the exhaust system, meaning from the headers to the tailpipe would be replaced with an integrated system that included half maximizing heat taken from the exhaust and half completely insulated, probably using a vacuum sleeve, and active cooling.

For this, it might even be better designed to have the hot end on the rear half, on a front engine car, seeming to mount a tube shaped thermoacoustic along the pipe, backwards. Maybe, maybe not. Keep an open mind on initial designs.

OK, so now you know thermoacoustics are indeed Stirling engines. They are also truly being used for industrial purposes. My own company, a fortune 500, uses their own design, commercially made, as the main cooing for chilling several ice cream brands you are very familiar with. These are no toys!

I will not post again here.
Relax dude.
This is all just fun and educational.

- Joe
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Response to Heat from auto rad and exhaust in to elctricity thru Stirling.

Postby lowee2855 » Mon Jun 23, 2008 8:51 pm

Why not forget about the ICE and just go with a Stirling, generator some batteries and electric motor? Keep a charge on the batteries. When they get up to full charge the Stirling cuts out. When the batteries get low the Stirling comes back on. You lose the weight of a starter motor, radiator, get rid of the power steering and power brakes cause thy are unmanly. You will need no muffler, fuel pump, O2 sensor, EGR valve, ECC, MAF sensor and all the other expensive Rube Goldberg junk.
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Response to Heat from auto rad and exhaust in to elctricity thru Stirling.

Postby poche » Fri Nov 14, 2008 12:41 am

NOt a Stirling.. but this is being done NOW...
GOogle Waste Heat Engine and find a company called
Cyclone Power Systems...

they have demonstrated an electric generator that runs off of
the exhaust heat of heavy trucks. It looks to me to be a
radial steam engine, possibly working at less than atmospheric
pressure to lower the boiling point of deionized water.
Could be very promising for concentrated solar collectors.
Wish I could buy one :-)



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