Another question about auto exhaust heat recovery

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matt___6775
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Joined: Fri Sep 02, 2005 7:31 pm
First Name: Matt
Last Name: Nolan

Another question about auto exhaust heat recovery

Post by matt___6775 »

I saw the question wether it was doable to run a Stirling engine off of auto engine heat to
produce eletricity and saw the answer that there probably wasn't enough heat to
economically produce the electricity. But what if you increased the temperature differential
by means of a system that could rapidly evaporate a liquid (like water or alchohol) that
would in turn dramatically decrease the temperature using the wind turbulence generated
by the movement of the car. Couldn't some sort of small patch on the side of the car have
a fabric that would refill using capillary action connected to a resevoir of water that could
be refilled every so often that would dramatically cool the cool side of the Stirling engine
when the car gets up to speed and starts rapidly evaporating the water? Could this
increase the efficiency of the Stirling for this application? Just a thought. Thanks!
binraking
Posts: 8
Joined: Mon Jun 18, 2007 10:31 am
First Name: David
Last Name: Ward

Response to Another question about auto exhaust heat recovery

Post by binraking »

Hello,

It would be necessary to crunch some numbers in order to give you even a WAG (wild ass guess) at to the efficiency of such a system, but here are some of the major factors that would have to be considered.


1. What would the surplus electricity be used for?

2. Is there a cheaper way to generate the electricity (other than using a Stirling engine to recover waste heat)?

3. How much surface area would be required (for reasonable temperature range) in order to generate enough evaporation?

4. Where would you put the tank of evaporant?

5. How would hauling the evaporant around affect fuel mileage?

6. What would be the initial and long term costs to the consumer?

7. What would be the benefit (bang for the buck)?

8. What do you do when it rains? Not much opportunity for evaporation when it rains, but one could catch the rain and use it to refill the evaporant tank.


I can already tell you there is a much more efficient way of handling vehicle exhaust heat. Eliminate it completely. In fact, eliminate all of the waste heat generated by the vehicles hydrocarbon fueled propulsion system by scrapping it in favor of one that generates a drop in temperature!


There are vehicles being used in France right now at this very moment that run on nothing more than compressed air. Thats right. You can breath their exhaust, and it is cool enough to be use as air conditioning! These vehicles emit nothing but AIR. Here are a couple of links to get you started, but try typing the words air car into Google and stand back!


http://www.theaircar.com/
http://www.gizmag.com/go/7000/


It looks like these cars are destined to be driven on every street ... Ah, I almost said in America, but right here at home is probably the last place you will see one. What I meant to say is that these air puffing little gems are destined to be driven everywhere but here. That is unless we get a grass roots movement started to convert/build our own on our own, since the American automotive manufacturers are way to busy wasting time developing hydrogen powered vehicles for which there is no infrastructure! Every service station in America already has an air compressor! Even your local Quickie Mart has a compressor to top up your tires with. Compressed air "fuel" technology would be very easy to merge with our exsisting infrastructure.


Where does a Stirling engine fit into this picture? Well, we need a power source to compress the air to put in our air powered car. We could mate a Stirling engine to the exhaust pipe of our local coal burning waste heat producing brute of a power station, and use that otherwise waste heat to compress air. And since air is pretty easy (and very non messy) to store. It would be easy to stockpile. And best of all if your air storage tank springs a leak nobody gets cancer!


We could pipe our "free" compressed air in the same way we pipe natural gas now. Imagine the growth potential for air-powered home appliances! A blow drier that actually runs on air! Oh My!


Seriously though, large scale stationary applications of Stirling engines are our best bet.


Think BIG! Someone once said that "If grasshoppers were as big as cows, we would all be eating grasshoppers".


V/R
Dave
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