Turbo-powered alternator
 

Why not use a cutout for the turbo so you can vary the amount of exhaust gases/pressure applied to the turbo? You could set it at a point where it would spin the alt within a certain rpm range. After all, an alternator has some resistance when putting out current. This would keep rpm down some. perhaps we could open the cutout when cruising and close it when driving with variable revs/load? This would keep the turbo rpm pretty stable. Just an idea....

A wastegate does this normally. Of course you have no intake pressure to push on the wastegate actuator anymore... I imagine you rig something up though.

you don't want the turbo to go slow or your response to power goes way down, big lag. What you don't want is to get to much back pressure that the turbo is restrictive because trying to keep the exhaust housing A/R small .

What turbo manufactures have done to improve the peak efficiency around wide rpm is .
1)variable geometry exhaust housing, this not used much in gas as temps to high but idea is a variable vanes/deflectors in the housing that can keep efficiency up over engine rpm band .
2) twin scroll housing, this is were the exhaust housing has two different A/R compartments,. one for low speed response and larger for high rpm . there a flap to control when it opens (there still normal wastgate still used) .RX7 used this for many yrs on there turbo 13b engines (87-91).
3)Sequential turbos , this is were there 2 turbos, its similar to twin scroll idea. One turbo is run at low speed/boost and then second kicks in . Later 92+ RX7 went to this system and so did Toyota supra turbo's at end.

There also some work on electric assist turbos which can use the turbo shaft to power systems like alternator .

here link to article on it .

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daox, I believe you still can have it.

if you cap off the part of the turbo that usually goes to the engine intake.

if you leave it open , then ye sure, you'd lose it.

if necessary, u can leave a hole in the cap you've installed.
this would now give a measure of control on the turbo, and the hole would keep the turbo from becoming too restricted.(a valve could be used to adjust the size of the hole too)

please correct me if i've made a mistake

To use a Turbo as an alternator would be quite difficult in my opinion,
The main reasons being:
1 / That turbo's are designed to spin from 30,000 & 100,000rpm and hence balancing is critical and any mistakes in setup will result in catastrophic failure, that's why there are specialists that just do turbo's.
2 / People have the misconception that exhaust gasses are just wasted energy, in some ways yes, but they do serve a major function for the engine even after they leave the cylinders. Exhaust designers try to maximise the flow of exhaust gasses down the pipes so the momentum actually creates a suction at the engine end which helps the engine clear the exhaust and draw in fresh air. So if you remove the exhaust, put any restrictions in (turbo) or cool it down too much, the engine will run less efficiently and any energy you extract will be lost through poor engine performance.
If you can hold the heat in the exhaust, it will flow much better and the engine will breathe more freely, remember the engine is only providing power 25% of the time the other 75% it is acting like a compressor, so clearing the back pressure in the exhaust is a crucial aspect to energy efficiency.
Probably better to look at insulation on the exhaust components, esspecially in the colder climates, this may also be a significant factor when people notice their FE is down in cold weather.
Improve the exhaust flow, engine runs more efficiently & FE goes up.

on #1 may I correct something here..
when hooking up such a setup you have a very small pully on the turbo and a very large one on the alternator. so the only part of this setup thats going 100k rpm is the turbo pully. even the belt isn't speeding, so the alternator certainly isn't. also you hook it up to bypass the exhaust gasses when the turbo gets up to a too high speed...

on #2. the racing guys say superchargers waste energy from the engine , and turbos don't, that why ultimately there's more power to be had from a turbo cuz the power driving the turbo would otherwise be wasted, unlike the supercharger. I'd imagine these racing guys usually know their stuff, and if thats true then the turbo alternator idea should be quite sound.

I'm not saying the idea is not possible, but it may not be practical with current technology. Anything spinning at such high speed needs extremly fine balancing and you'll need specialised pulleys & belts to ensure minimal losses.
Turbo's do draw power from an engine, but they push more air in so more fuel can be burnt and hence provide more power. Just like putting a wind generator on the roof it provides power, but creates drag. Put a turbo in the exhaust and yes it can provide power, but forms a restriction, which means less exhaust is drawn out of the cylinders, so less air in, so less efficiency.
Why do you think "racing guys" polish the inside of their exhaust manifolds & put on extractors, insulate the manifold etc. all these are to increase exhaust gas speed and let the engine breathe more freely.
It definately can be done, but the question is will you lose more efficiency from the engine than you gain in electricity.
Even the idea of using seebeck cells to generate electricity from the exhaust has an expense, to get any effective output you need to move heat through them, the more heat you move from the exhaust, the slower it flows and same issue again.
That's just my opinion, from what I have read and experienced myself.

I'm attracted to the idea of a turbo-alternator. One could feasibly use the turbo alternator to either (a) eliminate the need for a normal alternator, or (b) use it to power an electric assist motor, without the penalty of needing lower compression pistons, resulting in less efficiency when the turbo isn't running.

I assume you believe that putting a Turbo on the exhaust is free energy, if that is the case then I'll leave you to it, I think I've said enough on that topic.

Now when you talk about an electric assist motor, that's another idea and I think that it is more viable than the Turbo idea.

"TIGERS (Turbogenerator Integrated Gas Energy Recovery System) is a water cooled switched reluctance generator coupled to an exhaust driven turbine. It is capable of operating in exhaust temperatures > 900ºC, at speeds up to 80,000rpm, delivering a shaft power of 6kW"

Controlled Power Technologies... TIGERS

That's great, only problem is a non-hybrid vehicle has no way of using 6kW!
I want to try taking a rather large turbine and gearing it straight to the crankshaft via pulley, it would do best at high rpms where typical cam phasing systems have the exhaust opening earliest.

For just generating enough electricity, getting 300W from heat alone isn't horribly difficult I think. Aluminum heat exchanger, 2kg worth of thermoelectric generators, and aluminum waterblock will go a long way. This would cost several thousand dollars, but this turbine generator would too.

Good find,
I would like to see a side by side study done on two identical vehicles, one std the other with the Turbo generator for say 5,000km, then swap the turbo unit over to other vehicle. Use the same driver for bothe vehicles, but driver is not aware whether the vehicle is std or with Turbo Gen.
Everything else in the vehicles must be identical and just using an appropriate section (same length as turbo) in the exhaust on the non turbo vehicle, so flow charachteristics are not modified in any way.
Fuel economy could be compared effectively then.
That type of evaluation would then prove conclusively if it was a viable concept.

are u sure the thermoelectric generator is so expensive? have a look:

starting at like $5 POWER GENERATION TEG - HIGH TEMP THERMOELECTRIC PELTIER | eBay


and going up to $38
http://www.ebay.com/itm/THERMOELECTR...item27c36f54e4

it just depends on the item's size and power.
I'd imagine a bunch of these attached in the appropriate manner to the exhaust manifold (or farther down the pipe if it's too hot over there) should bring about enough power to run our ignition coil, headlights and fuel pump as necessary

the question is how do you hook them up properly...
I welcome all feedback

A Tmax of 180C is pretty useless for power generation. Sure you could use like 50-100 of them on your exhaust, but weight and cooling become a problem.

Commercially available ~300C peltiers that size are 100 dollars for about 15-20W capacity running at max delta T. If you're using the car's existing coolant loop at 90C even with an "intercooler", you'd be lucky to get more than 10W from each one.

In addition if you're running them at max temp, the ones I've seen put out 15V or so which is too high. If you wire that straight to the battery you'll end up bleeding off a few percent of the precious power through internal resistance.

Ideally we have the turbine for pressure recovery, and then the TEGs for heat recovery working together. On a hybrid car of course.

u sure? dont alternators charge at 14+ volts anyway and lose a drop as a result?

so 15v shouldn't be too terrible

14V is the limit for charging a battery, over that you damage it (I think). To safely provide thermoelectric power to the system it has to be at less than 15V, and you can do this by either converting it or intentionally reducing the capacity so that it bleeds off the voltage via internal resistance.

True, but note that 6kW is the max. shaft power - ie. the 2-litre ICE shown has to be going some to push the exhaust stream hard enough for 6kW, plus the best electrical efficiency is 90% and only for high voltage.
I still reckon $/kW a turbo-machine like this would be better value than the TEG option, at least until the technology matures. And providing, as you say, you can apply 6kW to something ... BAS (belt alternator starter) type hybrids aren't beyond the backyard tinkerer.
The costliest part for one off build of something like the TIGERS design would be the high-speed generator, but the turbo could be 2nd hand and relatively cheap.

I'd still go via the electrical route due to the differential in revs the turbo wants to run at against those of the engine, ie. at mid-revs say 2500 on 3/4 load the turbine will still be most efficient spinning near to it's maximum of 80k. Also there is no need to plumb in additional bypass on the exhaust.
With the power routed -> Turbo-Generator-PowerController-Motor a cut-out is easy, with no concerns about choking the gas-flow. Hey, throw in an ultracapacitor bank as well for that extra kick!

these dude's that I've ordered came in the mail the other day.
I tried them out by putting an inverted tin pan on the stovetop with a very small fire on. the inverted pan got quite hot and I tried the cells out on top of it.

they are useless. I had trouble getting the voltmeter to read .4v

when operating well they read like .32-.35v

total garbage.
if you put in 12v they get frightfully hot in 5 seconds but if you heat the unit you do not generate frightful electricity

all right, next idea please

you need ~ 46 of them in series to get ~14vdc (14v/.3v=46 units)

You also need to cool one side as you heat the other, if I'm not mistaken. It's the difference in temp between each side that does the work.

Maybe you can mount them on an old cool-box and use them to cool your beer! (or heat it if you get the polarity wrong)

Yep, without active cooling they're worthless. With active cooling you might be able to get a few volts out of it, but the problem isn't the volts, it's the total power. 300C, 60mm TEGs push less than 20W with >200C delta.

We don't even need higher efficiency TEGs to be able to use them on cars actually, we just need higher temperature ones. They're not commercially available though, to the best of my knowledge. Allowing 500C rated TEGs to interface with exhaust would mean a pretty simple and compact unit using perhaps 6 of them could supply all of the car's electrical energy.

Higher efficiency ones would be good when mild-hybrids become standard.

I bet they are going to act like solar panels where you need at least 17 to 18 votls open current to be able to push any useable amount of power onto the vehicles electrical system.
On my truck I use 3 panels wired up for 21.5ocv, hooked to the batteries at14.3 volts they push almost 0.4 amps, it keeps the batteries fully charged.

"when operating well they read like .32-.35v"
Just like a single solar cell.

Okay I found some slightly more reasonably priced 300C TEGs that are 75 bucks: http://www.espressomilkcooler.com//P...-12611-6.0.pdf

Hopefully the government money that went to GM for developing waste heat recovery wasn't all wasted and they get something to the market soon.

Knowing GM was likely wasted on something unfeasable or other wise uneconomical.

Yea :(
But I really hope someone makes skudderite 800-900K TEGs commercially available soon, they seem to have slightly better Z than most materials now, and something that can directly interface with exhaust more or less could be very effective. 1-2 pounds of TEG, a few more pounds worth of aluminum waterblock, a 2 pound radiator, hooked up to the existing cooling system, a DC-DC converter to prevent it from sapping power before the engine heats up, could easily provide almost all of the car's electrical requirements.

Oh and speaking of waste, I noticed that some of the companies doing TEGs were using a noble gas in a heat exchanger on the exhaust, rather than bolting the TEGs directly...what the hell? Did they do that to intentionally add weight and cost and make it seem unfeasible?

Just saying by the way, assuming electric supercharging systems haven't taken off by the time I get around to this, I intend to someday build a blowdown turbine for an NA engine connected to the crankshaft directly via speed reduction using a large twin scroll turbocharger and removing the compressor side. I'm thinking a GT47 or so geared down 9:1ish to a 2L engine. At 7000rpm or so it should hopefully make a healthy few horsepower, with some luck it could hit 10hp. It's okay that the turbine spins too slowly at lower rpm, since blowdown losses are lower at low rpm anyways.