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Exhaust waste heat recovery system

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bjohnson1234

Well Known Member
Has anyone looked at/thought about using an exhaust waste heat recovery system with a thermoelectric generator as a "backup alternator" for electronic ignition? Seems like it should easily be able to generate enough power to run most electronic ignition systems https://www.acs.org/pressroom/press...opter-exhaust-into-thermoelectric-energy.html
I'm not sure how much a system like this would weigh (probably not significant?), but if it used the heat of the pipes themselves (https://www.psu.edu/news/research/s...nd-hot-surfaces-turns-wasted-heat-electricity) rather than the exhaust gases there would be no other performance penalty.
 
I always thought it would be cool to do this with a turbocharger turbine and generator but also figured it would introduce reliability problems. I'm enamored of the idea that a valveless engine like a rotary would be the ultimate turbo compound engine.

Now, I would love to see the exhaust plumbed as a leading edge wing heater, for anti-ice capabilities using only wasted heat. I think it's possible that a piston single may not produce enough, but I'm not capable of doing the heat transfer math. Complexity aside, I can't figure out why someone hasn't done this with a turboprop exhaust yet.
 
None of these benefits will outweigh the associated penalties. Much more applicable to a ground based constant cycle. Best of luck.
 
Full Throttle said:
Assuming you drive 65 miles per hour for 150 hours (9000 minutes) . You would have to drive 9750 miles to fully charge a dead car battery.;)
But, I guess the charging energy is free. That's a good deal.
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I’m not talking about charging the battery, just the few amps needed to run the electronic ignition.
 
bjohnson1234 said:
If you are just using the heat of the pipe itself and don't have anything in the exhaust stream, what is the penalty other than weight?
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Any open cycle (Otto, Brayton, etc) is a poster child for inefficiency.

I'm a huge fan of conservation. Love trying to eek out the last bit of efficiency from any process. Nothing better than making money off of would-be waste but there are practical limits. As for the aforementioned open cycles, adding a bottoming cycle can increase the total cycle efficiency by 50%. This is complex and you're already on the steep part of the diminished returns curve; so, that recovery is best suited towards a high volume/low margin market (not ours).

You learned conservation of energy, mass, etc. in school. As an engineer, it took me a while to accept the realities of conservation of money. The sighted example is a good case in point. Yes there's the obvious weight penalty; but, there are hidden costs. An example would be the exhaust. That metallurgy needs to be allowed to cool through radiation and (free/forced) convection. Wrapping it in anything will shorten it's service life. So, where do the lines intersect between fuel savings from the "free" generation, the added fuel costs from weight of the primary system and it's ancillary equipment, and the cost of a shortened exhaust life including associated manpower costs? Maybe you could eek out a net positive on paper but I doubt it. Even then, is the complexity and potentially added service costs worth it?

A prime example of the BS above is the auto start/stop that a lot of new cars have. On paper, they save XXX gallons of gasoline in the car's lifetime. Once again, does it save more money than the shortened service life of a starter? Are the related environmental impacts from the brief stops less than those related to the mining of materials -> manufacturing of the replacement -> related waste of a replacement?

Ultimately there are better, proven, less complex ways to grab a few amps for our applications.
 
Freemasm said:
Any open cycle (Otto, Brayton, etc) is a poster child for inefficiency.

I'm a huge fan of conservation. Love trying to eek out the last bit of efficiency from any process. Nothing better than making money off of would-be waste but there are practical limits. As for the aforementioned open cycles, adding a bottoming cycle can increase the total cycle efficiency by 50%. This is complex and you're already on the steep part of the diminished returns curve; so, that recovery is best suited towards a high volume/low margin market (not ours).

You learned conservation of energy, mass, etc. in school. As an engineer, it took me a while to accept the realities of conservation of money. The sighted example is a good case in point. Yes there's the obvious weight penalty; but, there are hidden costs. An example would be the exhaust. That metallurgy needs to be allowed to cool through radiation and (free/forced) convection. Wrapping it in anything will shorten it's service life. So, where do the lines intersect between fuel savings from the "free" generation, the added fuel costs from weight of the primary system and it's ancillary equipment, and the cost of a shortened exhaust life including associated manpower costs? Maybe you could eek out a net positive on paper but I doubt it. Even then, is the complexity and potentially added service costs worth it?

A prime example of the BS above is the auto start/stop that a lot of new cars have. On paper, they save XXX gallons of gasoline in the car's lifetime. Once again, does it save more money than the shortened service life of a starter? Are the related environmental impacts from the brief stops less than those related to the mining of materials -> manufacturing of the replacement -> related waste of a replacement?

Ultimately there are better, proven, less complex ways to grab a few amps for our applications.
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Keep in mind here that the objective isn't efficiency per se, it's about the few amps needed to run electronic ignition in an emergency so it's weighed against the costs of a backup alternator. I don't know if it's a practical solution or if it makes any sense or not, just want to be clear about the goals.
 
Freemasm said:
A prime example of the BS above is the auto start/stop that a lot of new cars have. On paper, they save XXX gallons of gasoline in the car's lifetime. Once again, does it save more money than the shortened service life of a starter? Are the related environmental impacts from the brief stops less than those related to the mining of materials -> manufacturing of the replacement -> related waste of a replacement?
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This is an excellent analogy. It's such a dumb smart system that it will kill the engine when you plan to start moving again in 1-2 seconds. Turning it off is part of my "start checklist".

Freemasm said:
You learned conservation of energy, mass, etc. in school. As an engineer, it took me a while to accept the realities of conservation of money. The sighted example is a good case in point. Yes there's the obvious weight penalty; but, there are hidden costs. An example would be the exhaust. That metallurgy needs to be allowed to cool through radiation and (free/forced) convection. Wrapping it in anything will shorten it's service life. So, where do the lines intersect between fuel savings from the "free" generation, the added fuel costs from weight of the primary system and it's ancillary equipment, and the cost of a shortened exhaust life including associated manpower costs? Maybe you could eek out a net positive on paper but I doubt it. Even then, is the complexity and potentially added service costs worth it?
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I always wanted to exist in the "cost is no object" areas of engineering. I grew up hearing about things like the McLaren F1, which used gold foil as a radiant heat barrier because it was the best available material. The lack of common jobs that embodied that mindset led me to pursue a different career.
 
bjohnson1234 said:
Has anyone looked at/thought about using an exhaust waste heat recovery system with a thermoelectric generator as a "backup alternator" for electronic ignition? Seems like it should easily be able to generate enough power to run most electronic ignition systems https://www.acs.org/pressroom/press...opter-exhaust-into-thermoelectric-energy.html
I'm not sure how much a system like this would weigh (probably not significant?), but if it used the heat of the pipes themselves (https://www.psu.edu/news/research/s...nd-hot-surfaces-turns-wasted-heat-electricity) rather than the exhaust gases there would be no other performance penalty.
Click to expand...
Actually we were working on this concept a few years ago. We found good success with a clamp on exhaust device that could power dc loads pretty effectively. We used it to run a GRT Mini EFIS. The target market was experimental aircraft for backup power generation.
 
Cut up a pedal bike and mount it in your cockpit, hook up some wires and a small generator…pedal like hell the whole time you’re cruising to charge up your battery for that one day when your e-mag needs help.

Better yet…get you a rat in a wheel in the seat next to you to do the work for you…

Collect your table scraps and re-utilize for electricity via the “Rat-erator”.

If a rat isn’t up to the task…maybe switch to a “ferret-erator”

Man…this could be big. You guys can say you knew me before Hartzell buys me out.
 
justa6ereh said:
Cut up a pedal bike and mount it in your cockpit, hook up some wires and a small generator…pedal like hell the whole time you’re cruising to charge up your battery for that one day when your e-mag needs help.

Better yet…get you a rat in a wheel in the seat next to you to do the work for you…

Collect your table scraps and re-utilize for electricity via the “Rat-erator”.

If a rat isn’t up to the task…maybe switch to a “ferret-erator”

Man…this could be big. You guys can say you knew me before Hartzell buys me out.
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Thanks! Got a chuckle to start my day! :)
 
justa6ereh said:
Cut up a pedal bike and mount it in your cockpit, hook up some wires and a small generator…pedal like hell the whole time you’re cruising to charge up your battery for that one day when your e-mag needs help.

Better yet…get you a rat in a wheel in the seat next to you to do the work for you…

Collect your table scraps and re-utilize for electricity via the “Rat-erator”.

If a rat isn’t up to the task…maybe switch to a “ferret-erator”

Man…this could be big. You guys can say you knew me before Hartzell buys me out.
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Hell if BS could be harness as power you might never need buy avgas again.
 
Bman0429 said:
Actually we were working on this concept a few years ago. We found good success with a clamp on exhaust device that could power dc loads pretty effectively. We used it to run a GRT Mini EFIS. The target market was experimental aircraft for backup power generation.
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So who is "we", and as everyone knows, without pictures it didn't happen.
 
DanH said:
So who is "we", and as everyone knows, without pictures it didn't happen.
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A partner and I began working on that as Altegsystems back in about 15 years ago. Presented at Oshkosh raised a little money with intentions of converting turbine heat exchangers to TEGS.

But on the small aircraft front we tested on an old Cherokee 180 as a test stand and a couple home builts for airborne testing. It was effective for powering small loads and it was super simple with no moving parts at all. Basically an split aluminum block the clamped on to the exhaust pipe a couple of TEGs a couple heat sinks and a buck boost converter to get the right voltage. Then you could connect whatever you want to it.
 
The article goes on to say that a piston engine would create the power of 5 lithium-ion 18650 batteries.

Like Electric automobiles. I think they will be really great in about 20 years…..


IMG_8342.webp
 
DanH said:
So who is "we", and as everyone knows, without pictures it didn't happen.
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Im sure I still have that stuff in a box someplace if yall are interested i could dig it out. As a concept and in practice it worked. If you Google alteg systems you'll find some old stuff about what we were doing. We still make nose wheel forks for canards.

What i love about the homebuilders is they're always looking to improve their rigs
 
skirting_virga said:
This is an excellent analogy. It's such a dumb smart system that it will kill the engine when you plan to start moving again in 1-2 seconds. Turning it off is part of my "start checklist".

Don’t know what kind of car you drive but there are products out there that defeat the auto stop.

We are driving a newer ford expedition. The product we bought was about $80 and took less than five minutes to install. Automatically disables the auto stop every time you start the car…
I always wanted to exist in the "cost is no object" areas of engineering. I grew up hearing about things like the McLaren F1, which used gold foil as a radiant heat barrier because it was the best available material. The lack of common jobs that embodied that mindset led me to pursue a different career.
Click to expand...

Don’t know what kind of car you drive but there are products out there that defeat the auto stop.

We are driving a newer ford expedition. The product we bought was about $80 and took less than five minutes to install. Automatically disables the auto stop every time you start the car…
 
Not feeling very smart today so I'll ask. What is the virtue of this product?

For it to make watts, it needs exhaust heat.
If the engine is making exhaust heat, it can turn a primary and/or back-up alt/gen.
If the engine isn't making exhaust heat, you're on battery(ies) power regardless.

So:
For normal ops, what is the value added?
What is the added safety margin for off-nominal ops?
If "efficiency" is the only goal, the benefits are down in the mud/

What am I not seeing?
 
Freemasm said:
Not feeling very smart today so I'll ask. What is the virtue of this product?

For it to make watts, it needs exhaust heat.
If the engine is making exhaust heat, it can turn a primary and/or back-up alt/gen.
If the engine isn't making exhaust heat, you're on battery(ies) power regardless.

So:
For normal ops, what is the value added?
What is the added safety margin for off-nominal ops?

What am I not seeing? That's a fair question
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That's a fair question. Consider the fact that running a primary power source or a second alternator is not free. You're using some portion of the energy that that engine produces to create that energy and that has some effect on fuel burn. The heat energy that's created from the combustion process is mostly a byproduct that is unused. So why not put that thermal energy to work Beyond heating the cabin. At least that was what the thought was. On a larger scale those fuel efficiency arguments start to carry a bit more weight. But it's not without trade-offs.
 
My real point is the benefit doesn’t out weight the added complexity, potential hidden costs, etc.

I love TEGs/TNGs in the right application (non-terrestrial). They are stone simple. For everything else, their single digit efficiency is easily outpaced by most anything else. Though against most of our natures, sometimes you just have to accept the inherent inefficiencies and move along.
 
Freemasm said:
My real point is the benefit doesn’t out weight the added complexity, potential hidden costs, etc.

I love TEGs/TNGs in the right application (non-terrestrial). They are stone simple. For everything else, their single digit efficiency is easily outpaced by most anything else. Though against most of our natures, sometimes you just have to accept the inherent inefficiencies and move along.
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Just to be clear I'm not trying to sell anything. But somebody asked a question about how that works and how would it work and I thought I would contribute to the discussion. Everything in aviation is a trade-off. We trade the inefficiency of air-cooled engines for the superior power production of liquid cooled engines. Because we care about reducing complexity and weight and reliability. Doesn't mean that a liquid cool engine is not better. Nor that it doesn't have a use case. Most single engine aircraft operate with a single alternator and a backup as the battery. Alternator dies mags keep working engine keeps running and you got the battery to get you someplace where you can get on the ground. But what if you could have a second alternator that didn't have belts that didn't require parasite consumption off of the primary engine. Now if your primary alternator craps out you're not limited to operating only on what your battery will do maybe you can carry on home.

Hopefully this added to the discussion
 
Napkin math
30a backup generator at 14v is 420 watts, or almost 0.6 hp

O-360 running rich at 65% is 10gph, for 117hp. That's 0.05gph to turn the generator at max capacity. It's not as insignificant as it sounds. That's a beer can's worth of gasoline in a 2 hour flight. Fly 100hrs a year, that's 5 gallons of gas.

The real benefit could be from a simpler and potentially more reliable design. We see lots of threads about alternator reliability.

Downside is that it won't be very powerful on the ground or at low power settings. A descent from high altitude could be a long time running on battery power. From 15,000ft with a 500fpm descent for 30 minutes might be enough to just about deplete a battery.

It's an interesting idea that I'd like to know more about.
 
The idea of "doomsday" backup power is one which easily captures the mind, particularly in aircraft which require electrons to allow the engine to continue to run.

As David Z indicates, a low power descent might make a thermal generator less-than-practical. (That's my term for it - call it what you will, we're using heat to directly make electricity so I think of it as a thermal generator.)

Looking at the world of classic taildraggers, where many aircraft of that era had no electrics whatsoever, I'm struck by the number of them which have been retrofitted with wind-driven generators. I'm equally struck by the way those generators can produce power on the ground when installed in a location downstream of the prop.

This all leads me to wonder if, in the "doomsday" scenario where we've been flying our electrically-dependent aircraft and we lose generation ability but still have to get the aircraft back on the ground in one piece, would a small ram air turbine (RAT) be a better idea? This could be a device which is tucked up into the belly or a wing skin and manually deployed only when needed. Perhaps it would be sized so that it would generate sufficient power to keep the engine running at a speed slightly below stall speed, such that power would be assured in all phases of flight but not necessarily once the aircraft is safely on the ground.

As always, I'm interested to learn from the vast wealth of experience in this group...
 
David Z said:
Napkin math
30a backup generator at 14v is 420 watts, or almost 0.6 hp

O-360 running rich at 65% is 10gph, for 117hp. That's 0.05gph to turn the generator at max capacity. It's not as insignificant as it sounds. That's a beer can's worth of gasoline in a 2 hour flight. Fly 100hrs a year, that's 5 gallons of gas.

The real benefit could be from a simpler and potentially more reliable design. We see lots of threads about alternator reliability.

Downside is that it won't be very powerful on the ground or at low power settings. A descent from high altitude could be a long time running on battery power. From 15,000ft with a 500fpm descent for 30 minutes might be enough to just about deplete a battery.

It's an interesting idea that I'd like to know more about.
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Except the alternator is not pulling full load all the time. It pulls enough to top off the battery after starting, and then enough to maintain whatever live electrical load is online during flight - but definitely NOT full load all the time.
 
airguy said:
Except the alternator is not pulling full load all the time. It pulls enough to top off the battery after starting, and then enough to maintain whatever live electrical load is online during flight - but definitely NOT full load all the time.
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Let me see if I can dig out my bench test rig and get some videos put out. But surprisingly even at idle speed on the engine it puts out enough watts to run one of these Mini eadis. Again we were very much still prototyping and testing that stuff. But a lot of the things that people are putting forward were things that we evaluated and were able to knock down pretty easily. It's a pretty significant delta T even at idle. Consider at altitude the outside air temperature is lower and ostensibly your engine exhausttemperature is higher
 
airguy said:
Except the alternator is not pulling full load all the time. It pulls enough to top off the battery after starting, and then enough to maintain whatever live electrical load is online during flight - but definitely NOT full load all the time.
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Why not install a naca duct in the belly or some other convenient location which a slider valve on it. If needed open the slider valve to turn on the air flow which would operate a small alternator.
 
I hate being the naysayer here…but it’s kinda like my wife buying this silly little battery powered milk spout that sprays milk all over the fridge, when the trigger is bumped…all for the sake of saving the effort of pouring from a plastic jug.

Solving a non-problem.

Yes, SureFly and P-mag is nice…but having my trust Bendix has convinced me to stay with it. In fact after flying with electronic mags I’ve realized fixed timing is fine, unless I intend to climb way high and lean way back…for that trip, I don’t mind flipping the switch, but the rest of the time, no need.

Solving this excess heat, into electricity is the same. Solving a non-problem.

I’ve flown all over the place and never would this have made a difference for me. Spark plug…sure, flat tire, yep…lousy gas.. bad starter, uh huh…but this?

Nope. Not ever. Non-problem, which doesn’t need a solution.
 
Go ahead, build it, work out the bugs, make it reliable and available. And then we can evaluate something real. Right now we can't.

Bman049's device possibly excepted, and few details were revealed about that one.

Dave
 
In 35 years of flying airplanes from the very biggest to the smallest ive never had use for a ballistic parachute. Does that mean there is no use case? They have no value? That theyre silly little toys a kin to something my wife buys that sprays milk in the fridge?

There's a litany of things on an airplane that are there just incase.

Having a single source of power generation is a real problem. Batteries may get you someplace safe to land but wouldn't it be of value to be able to continue to your destination or return home? That's what the op was curious about and as someone who worked on the concept I thought it might merit some discussion about how it worked and what we did and what didn't work.
 
justa6ereh said:
Yeah…funny…I’ve flown a lot too…and a whole bunch of different sizes and types…never saw the value in a ballistic chute either.
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Oh you're that guy huh?! You sound like me waxing poetic about the days of fixed card NDBs and such lol.

They sure do sell a lot of airplanes with those things though.
 
bjohnson1234 said:
Has anyone looked at/thought about using an exhaust waste heat recovery system with a thermoelectric generator as a "backup alternator" for electronic ignition? Seems like it should easily be able to generate enough power to run most electronic ignition systems https://www.acs.org/pressroom/press...opter-exhaust-into-thermoelectric-energy.html
I'm not sure how much a system like this would weigh (probably not significant?), but if it used the heat of the pipes themselves (https://www.psu.edu/news/research/s...nd-hot-surfaces-turns-wasted-heat-electricity) rather than the exhaust gases there would be no other performance penalty.
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www.sciencedirect.com

Feasible application of thermoelectric generators in light aviation

Energy consumption in aviation is steadily increasing, requiring new technological solutions to reduce emissions and enhance sustainability. To addres…
www.sciencedirect.com www.sciencedirect.com
 
I’m actually the guy who prefers airplanes for missions. The RV is the perfect “a little of everything” aircraft…so I keep it that.

It will never be all things, and the flip side of total performance is total compromise. I’m good with that.

I’m also extremely good with anyone doing what feels right to them. As Experimental aviation is concerned, if you want yours doing something different than I want mine doing…it’s all good.

I’m also the guy that when cruising along and the whole electronic goody crapped out two years ago…was glad to have old school needle, ball and airspeed, to not only complete the flight, but to safely fly home…so…scold away…but simpler is better where RV’s are concerned…just my own little humble opinion and world.

Beyond that, I’ll go back to wiping up spilled milk in the fridge.
 
justa6ereh said:
I’m actually the guy who prefers airplanes for missions. The RV is the perfect “a little of everything” aircraft…so I keep it that.

It will never be all things, and the flip side of total performance is total compromise. I’m good with that.

I’m also extremely good with anyone doing what feels right to them. As Experimental aviation is concerned, if you want yours doing something different than I want mine doing…it’s all good.

I’m also the guy that when cruising along and the whole electronic goody crapped out two years ago…was glad to have old school needle, ball and airspeed, to not only complete the flight, but to safely fly home…so…scold away…but simpler is better where RV’s are concerned…just my own little humble opinion and world.

Beyond that, I’ll go back to wiping up spilled milk in the fridge.
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Get a cat, let it do the clean up in the fridge.
 
justa6ereh said:
Yeah…funny…I’ve flown a lot too…and a whole bunch of different sizes and types…never saw the value in a ballistic chute either.
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No safety device has value until you need it. I try to make a habit of periodically scanning around to see where I might be able to land if I lost an engine. There have been plenty of times where the answer was “this would be a really bad place to lose an engine”
 
Ironically I thought about this today- a few years ago I came across a coffee cup sized fire pit for camping that would charge a phone or power a string of lights. I could rip that apart wrap it around the exhaust and charge my iPad for free. I already have a cigarette lighter and excess amperage from the battery, but what fun is that?
 
This has me thinking of the old turbocompound engines from the likes of the Super Constellation.

They harnassed exhaust energy with a turbine. Through a fluid coupling, and added power to the crankshaft. It was good for several hundred horsepower. They were also notoriously complicated and unreliable.

If this thermal generator type device is capable of producing sufficient electrical power at idle, it must be capable of making LOTS of excess power on takeoff, climb and cruise. That excess capability could be wired to an electric motor on the vacuum pad, and providing additional power to the engine. Just like the turbocompound engines of old, but using only heat, and electrically coupled.
 
David Z said:
If this thermal generator type device is capable of producing sufficient electrical power at idle, it must be capable of making LOTS of excess power on takeoff, climb and cruise. That excess capability could be wired to an electric motor on the vacuum pad, and providing additional power to the engine. Just like the turbocompound engines of old, but using only heat, and electrically coupled.
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I think the EGT range is from maybe around 1000F to 1500F so it’s only generating 50% more heat and that translates into way less than 50% more power generated. CHT is a closer proxy for power generated. EGT is a measure of how (in)efficient your engine is at converting combustion into useful work. This is why it makes sense that the power output is relatively stable from idle to full power. You have an order of magnitude temperature differential between the exhaust and the air flowing through the cowl so a few hundred degrees one way or the other isn't going to make a significant difference.

Although I think most of these types of devices are just getting the heat of the pipe and not the exhaust gas itself and not sure what those temps are. If your TEG was part of the pipe itself near the exhaust port then you could get even more power out of it, but probably a short life.
 
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Now you guys have me going back thru my notes and research. for education have a look at some of this stuff.

Here's a link to a performance calculator where you can adjust the hot side and cold side temperatures for some of the best in class TEGs. We use the HZ-20 in our test rigs
 
bjohnson1234 said:
I think the EGT range is from maybe around 1000F to 1500F so it’s only generating 50% more heat and that translates into way less than 50% more power generated. CHT is a closer proxy for power generated. EGT is a measure of how (in)efficient your engine is at converting combustion into useful work. This is why it makes sense that the power output is relatively stable from idle to full power. You have an order of magnitude temperature differential between the exhaust and the air flowing through the cowl so a few hundred degrees one way or the other isn't going to make a significant difference.

Although I think most of these types of devices are just getting the heat of the pipe and not the exhaust gas itself and not sure what those temps are.
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you'd be surprise how much heat you can transfer from something clamped on to an exhaust pipe. We regularly saw temps in the 500-600 degree range. Even cooked a few TEGs. I'm looking for some of the CAD model stuff.
 
David Z said:
This has me thinking of the old turbocompound engines from the likes of the Super Constellation.

They harnassed exhaust energy with a turbine. Through a fluid coupling, and added power to the crankshaft. It was good for several hundred horsepower. They were also notoriously complicated and unreliable.

If this thermal generator type device is capable of producing sufficient electrical power at idle, it must be capable of making LOTS of excess power on takeoff, climb and cruise. That excess capability could be wired to an electric motor on the vacuum pad, and providing additional power to the engine. Just like the turbocompound engines of old, but using only heat, and electrically coupled.
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TO produce that kind of power you'd have to make an unacceptable weight trade off imo.
 
Bman0429 said:
you'd be surprise how much heat you can transfer from something clamped on to an exhaust pipe. We regularly saw temps in the 500-600 degree range. Even cooked a few TEGs. I'm looking for some of the CAD model stuff.
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Yeah I noticed the TEG you referenced had a continuous operating temperature limit of 480F (750F intermittent) so figured it must be somewhere in that range for the outside of the pipe. If they were regularly in the 500-600F range that explains why you cooked a few :)
 
bjohnson1234 said:
Yeah I noticed the TEG you referenced had a continuous operating temperature limit of 480F (750F intermittent) so figured it must be somewhere in that range for the outside of the pipe. If they were regularly in the 500-600F range that explains why you cooked a few :)
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yeah we started out with a copper hot shoe because I mean MAXIMUM EFFORT!! Those got nice and hot. Manufacturer didn't think that was possible. I was like we are pilots hold my beer!
 
Bman0429 said:
TO produce that kind of power you'd have to make an unacceptable weight trade off imo.
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Also, the accessory gear box is designed to provide power. I wonder if it's capable of being driven by 5hp. Maybe the conventional alternator location on the front, with a sturdier belt system is better?

Lots of potential that is certainly worth exploring. Nobody is selling a product yet, so I'm not condemning any idea until it is explored further.
 
B&C made a small alternator that fit in the vacuum pump pad. I used to have their small 8 am one on my first 4…worked great. It was a permanent magnet type alternator and worked as advertised to re-charge the battery.

I have a 15 amp one now, same location…

Considering the weight which for the small one was like 2.4 pounds, it made sense, much more so that adding additional heat processing equipment in the close proximity of fuel, as it being discussed,

Nice part of those, is you can completely have a separated small Earthx that could be easily crossed over in a pinch….not sure what pinch…but if your alternator took a dump….and you wanted to fly home, if you had mags…you could certainly run a few things…like a small gps, or a com radio for a bit …
 
Absolutely just saying when it comes to TEGs getting that kind of power on a light aircraft it is an unfavorable compromise imo. Not impossible but....
 
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