Exhaust Driven Alternator

[toc]

Reading over this article, Browser Warning

It dawned on me, why not drive the alternator with exhaust gas instead..
Similar concept to a turbo charger, except just use the velocity of the exhaust in a carefully designed generator system to drive charge.

For mainstream use it'd have to be able to recover the entire starting current draw within some short time of idle..

[HydroJim]

not sure it would be wise to have the electronics near something that hot, so you'd have to have a turbo belt system that connected the "exhaust to rotational velocity" piece to the alternator which adds complication and cost to the system.

[some_other_dave]

Not sure why this is in the Unicorn Corral. It has been discussed in other forums on this site as well.

I'm not sure how useful it would be, but it at least has potential to help. It would be interesting to see how the efficiency of the engine is affected by the exhaust restriction, and how quickly it could help recharge the battery.

-soD

[ksa8907]

I can't imagine how it would help. You'd have to put such restriction on the exhaust to build up enough pressure that the engine would start burning a fair amount of fuel just to compress/pump the exhaust. Energy is energy. Maybe rethinking the alternator efficiency is a better idea?

[justme1969]

Yes I did pose the question of what is the most efficient new alternator last month.

ps the best ive found was on a scca car and its belt ran off the rear axle of a mustang.
Not sure about water intrusion issues would just blow the diode im sure.

[groundflyer]

FYI I have seen one working off the turbocharger on a big rig a one off 10 years ago

[some_other_dave]

Originally Posted by ksa8907

I can't imagine how it would help. You'd have to put such restriction on the exhaust to build up enough pressure that the engine would start burning a fair amount of fuel just to compress/pump the exhaust.

Turbocharged cars seem to be able to use the compressor to stuff more air in without prohibitive amounts of restriction on the exhaust. I could see there might be a way to make it work.

The biggest problems would be heat, and gearing the 100K RPM of a compressor wheel down to something that a standard alternator or generator would work reasonably with.

Could be insurmountable problems, sure. But I don't think that warrants including this in with all the other unicorn poop.

-soD

[UltArc]

Originally Posted by ksa8907

I can't imagine how it would help. You'd have to put such restriction on the exhaust to build up enough pressure that the engine would start burning a fair amount of fuel just to compress/pump the exhaust. Energy is energy. Maybe rethinking the alternator efficiency is a better idea?

Cars need [in many cases, for optimum use] back pressure. And as soD said, turbo charged cars do fine with it. Well, more than fine lol

As efficient as the driveline/axle alternator would work, it still slows the car down. This seems pretty brilliant, since the exhaust happens when the engine is on.

[dmodified1]

actually thats not a bad idea use a system like the volt, hybrid tech not drive. have an I4 turbo diesel powering two HI output "exhaust driven" alternators. The alternators then power the electric drive of the vehicle. the obvious problem is heat to help this issue 2 generators would be used if more power would be needed the rpm of the diesel motor would be ramped up

[mwebb]

..."Cars need [in many cases, for optimum use] back pressure"...

engines ?
do not need back pressure in the exhaust , less back pressure is always better (except during decel)
which is one reason some users of
engines
use
headers , to minimize and or completely eliminate exhaust back pressure at certain
designed for rpm / load conditions

but
on decel
back pressure in the exhaust is irrelevant OR desired for braking purposes
and the engine intake has high vacuum during decel , so it would be easy to use vacuum to switch a valve to direct exhaust flow to spin an alternator
during decel only