Exhaust waste heat recovery system

[Bman0429]

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 …

Heat processing equipment in close proximity of fuel? What does that mean. The device we tested was similar in weight to the b an c and more output and zero moving parts no splints gears stator or windings.

Pretty clear you hate the idea but are you adding anything to the discussion about TEGs as a power source?

Happy to keep sharing

 

[justa6ereh]

Heat processing equipment in close proximity of fuel? What does that mean. The device we tested was similar in weight to the b an c and more output and zero moving parts no splints gears stator or windings.

Pretty clear you hate the idea but are you adding anything to the discussion about TEGs as a power source?

Happy to keep sharing

my response was directly after David asked about supplying power from the accessory drive.

That product is out there already and just letting him know about B&C

Wasn’t directed your way at all.

I don’t hate ideas…I do question ones that don’t seem to offer reasonable up-sides without excessive risk. Placing equipment in an engine bay, near fuel…such as is the case with an RV, always concerns me for my own ship…what you do, I am entirely supportive of. Questioning weight, cost, safety should be part of the expected responses though…when you post something, I think.

I’ve posted lots of my thoughts, mostly on operations of RV’s…and I always expect some criticism…no harm, no foul.


I hope that clears up my reply. No offense intended whatsoever.

 

[bjohnson1234]

my response was directly after David asked about supplying power from the accessory drive.

That product is out there already and just letting him know about B&C

Wasn’t directed your way at all.

I don’t hate ideas…I do question ones that don’t seem to offer reasonable up-sides without excessive risk. Placing equipment in an engine bay, near fuel…such as is the case with an RV, always concerns me for my own ship…what you do, I am entirely supportive of. Questioning weight, cost, safety should be part of the expected responses though…when you post something, I think.

I’ve posted lots of my thoughts, mostly on operations of RV’s…and I always expect some criticism…no harm, no foul.


I hope that clears up my reply. No offense intended whatsoever.

What exactly is your fire concern? The exhaust pipe is already very hot, this is just harnessing some of that heat (or rather the differential between that heat and the air flowing through the cowl) to generate a few amps of power. If you have fuel leaking in your cowl it seems like a TEG attached to your exhaust pipe is the least of your concerns?

 

[airguy]

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.

You are receiving realistic market feedback about your potential product here. Ignore it if you like. Go spend your money for R&D, develop and market the product, and see how it performs in the market.

One of us is going to get surprised...

 

[Freemasm]

Something to consider.

As I mentioned, I’m a fan of TEGs and TNGs in the right application. Doing what the OPs are doing would be a lot of fun if you had the time to commit to it Before committing any real money to it, some questions need to be asked.

When attempting to penetrate a market:
- Does this product do something others don’t?
- Will it be cheaper than the competition?
- Will it offer more for equal dollars?
- (For this market) Will it be lighter, all other things being equal?

If no one ever challenges the status quo, changes are doomed to be incremental. Have fun. Learn a lot. Be careful with your money.

 

[airguy]

Maybe you're going about this from the wrong direction? The heat/electrical conversion process is real - but what about using it the other way around? How about Peltier Junctions all around the cylinder head for cooling instead?

 

[Bman0429]

You are receiving realistic market feedback about your potential product here. Ignore it if you like. Go spend your money for R&D, develop and market the product, and see how it performs in the market.

One of us is going to get surprised...

if I wasn't clear before let me reiterate I'm not trying to sell anything. That project was shelved 15 years ago. Somebody asked about the concept and I was willing to post some information about it. Thats really all. Just sharing information to prove that it is feasible from someone who's actually ran with the notion.

How does it work? What materials did you use? what kind of power output did you find? How did the testing go. Where can I find more information? Was what I thought might happen.

Instead its opinions about marketability, operational necessities, suppositions about why it won't work lampooning about her rich schemes a delusions to comparing a concept to their wife's milk pump. Lmao.

I bet the op feels really supported.


Well in gonna leave you guys to it

 

[inktomi]

What about using the hot air from the oil cooler as a source of hot air instead of using a heat muff?

 

[mstrauss]

if I wasn't clear before let me reiterate I'm not trying to sell anything. That project was shelved 15 years ago. Somebody asked about the concept and I was willing to post some information about it. Thats really all. Just sharing information to prove that it is feasible from someone who's actually ran with the notion.

How does it work? What materials did you use? what kind of power output did you find? How did the testing go. Where can I find more information? Was what I thought might happen.

Instead its opinions about marketability, operational necessities, suppositions about why it won't work lampooning about her rich schemes a delusions to comparing a concept to their wife's milk pump. Lmao.

I bet the op feels really supported.


Well in gonna leave you guys to it

Thank you for adding your input. I find the subject interesting, and glad that someone with knowledge was willing to share. Please don’t let negativity discourage you or others from participating.

 

[justa6ereh]

It’s a funny thing here…35 years ago when we built airplane from a box of metal..the advice from Van was “ keep it light”. He wasn’t even a believer in constant speed props back then. My first -4 was 180hp. Fixed pitch and tipped the scales at 918lbs and flew exceptionally… We didn’t need primers, beacons, nav lights, adsb…didn’t need anything not pertinent to going flying.

As I’ve watched over the years, electric trim, glass cockpits, autopilots, leather interiors etc…you seldom find a 4 under 1,000lbs these days and somewhere along the lines, the use seemed to change, we went from fun flying to all weather cross country platforms.

Going back to when heat muffs were first starting to get added….I recall thinking….Why would you ever need cabin heat? Over time, as the aircraft role changed, I watched it change from a bunch of fighter pilots…flying formation and aerobatics to transportation, rather than pure fun.

As to the exhaust heat generator concept, the first thought to my engineering brain is differential cooling of the exhaust tube concerns, these are cheap 300 series stainless tubes and to affect the differential heating retention and altered cooling specifically at localized and concentrated areas, combined with increased weight of the device, regardless of what it is, makes me think cracks in the exhaust tubes will begin showing up frequently.

Now regardless of what one thinks of cracked exhaust tubes…I will assert that they can be quite catastrophic. The continuous cycling of a metal such as 300 series stainless and changing how that heat will be retained in some areas different to others, is dangerous territory to experiment with in this humble engineers mind.

Old things are new again…heat muffs, leading to cracks. Takes me back…

so…sorry if my analogy of spilled milk spouts, as solving a problem that doesn’t need solving…but this is a forum, where people think and offer opinions.


My opinion is that this idea would be more of a personal gadget for an aspiring creator, and one which posed more safety concerns than worth. (At least for my needs)


These days, I like my blended airfoil constant speed prop…still see no need for a primer, do like my feet warm in the winter months…but still remain committed that I don’t need a bunch of ancillary things that need additional maintenance and pose hazards to my well being of going flying.

I’ll rest on the notion that since it’s 2026…if this was such a great idea…Cessna, Beech, Cirrus, Piper, Robinson, And many more would probably be doing it already. They probably know that cracked exhausts are expensive and dangerous and most likely have the lawsuits to prove it.

 

[DanH]

How does it work? What materials did you use? what kind of power output did you find? How did the testing go. Where can I find more information? Was what I thought might happen.

Me too, and I'd like to hear it all.

 

[Full Throttle]

What about using the hot air from the oil cooler as a source of hot air instead of using a heat muff?

That's what Velocity aircraft has.

 

[rocketman1988]

"...If no one ever challenges the status quo, changes are doomed to be incremental..."

That is a TRUE statement.

 

[rocketman1988]

Thank you for adding your input. I find the subject interesting, and glad that someone with knowledge was willing to share. Please don’t let negativity discourage you or others from participating.

+1 I'd like to hear more; not saying I would use it at this time but I am certainly interested in the engineering.

 

[Freemasm]

+1 I'd like to hear more; not saying I would use it at this time but I am certainly interested in the engineering.

Want a gross over simplification? It’s a thermocouple on steroids. There’s a junction of dissimilar metals similar to a TC. Heat (delta T really) induces a proportional (milli)volt potential at the junction; thus, a current flow. Been away from the tech for many decades so I’m sure the materials have changed/improved. I’d also expect the efficiencies are still single digit or close. So why would the use of there ever make sense?

Satellites and some other extraterrestrial craft utilize them. Spent radioactive fuel, still thermally hot, is the heat source. It’s gonna stay thermally hot for many decades and the reference T is often outer space. The very heavy weight penalty from containment isn’t a factor once deployed. They are very reliable as they are stone simple. Great system whew appropriately applied. Hopefully the OP or other cognizant person will fill in the real details.

 

[David Z]

my response was directly after David asked about supplying power from the accessory drive.

That product is out there already and just letting him know about B&C

Wasn’t directed your way at all.

I don’t hate ideas…I do question ones that don’t seem to offer reasonable up-sides without excessive risk. Placing equipment in an engine bay, near fuel…such as is the case with an RV, always concerns me for my own ship…what you do, I am entirely supportive of. Questioning weight, cost, safety should be part of the expected responses though…when you post something, I think.

I’ve posted lots of my thoughts, mostly on operations of RV’s…and I always expect some criticism…no harm, no foul.


I hope that clears up my reply. No offense intended whatsoever.

I'm wondering if this concept is capable of providing reasonable power iNTO the accessory drive. A 30amp electrical supply draws 0.6 hp at max load. Can we hook up a 5hp motor and add 5hp to the accessory drive? Meaning an additional 5hp added to the crank and thus, the propeller. If 5hp can be harassed from the exhaust, I'm happy to harness that energy. But only if it can be done at a reasonable weight and cost. (Yes, there's lots being wasted out the exhaust. I picked 5hp for argument's sake).

 

[rocketman1988]

Want a gross over simplification? It’s a thermocouple on steroids. There’s a junction of dissimilar metals similar to a TC. Heat (delta T really) induces a proportional (milli)volt potential at the junction; thus, a current flow. Been away from the tech for many decades so I’m sure the materials have changed/improved. I’d also expect the efficiencies are still single digit or close. So why would the use of there ever make sense?

Satellites and some other extraterrestrial craft utilize them. Spent radioactive fuel, still thermally hot, is the heat source. It’s gonna stay thermally hot for many decades and the reference T is often outer space. The very heavy weight penalty from containment isn’t a factor once deployed. They are very reliable as they are stone simple. Great system whew appropriately applied. Hopefully the OP or other cognizant person will fill in the real details.

I get how they work, I was more interested in the application engineering for our aircraft.

 

[bjohnson1234]

btw I have no interest in producing a commercial product. I'm happy to share any results, but I was only looking for something for me.

Moving away from "can this produce enough power to be useful" which I think it can for my purposes, could strapping this thing to the exhaust pipe cause any stress/fatigue? It wouldn't make sense to trade an exhaust pipe for 50W of power.

 

[justa6ereh]

btw I have no interest in producing a commercial product. I'm happy to share any results, but I was only looking for something for me.

Moving away from "can this produce enough power to be useful" which I think it can for my purposes, could strapping this thing to the exhaust pipe cause any stress/fatigue? It wouldn't make sense to trade an exhaust pipe for 50W of power.

Fatigue in welded tubes comes in lots of forms… from a pure weight perspective, maybe not a huge deal, but not knowing if this would be one pound or five, it could make a difference. Subjected to a few g’s and a varying bunch of vibration? It definitely could. How it would be supported and what other piece of structure would bear that weight would be good know.

Only way to really know is build one and test.
If you shared a basic weight… and how you’d see it connecting to whatever comes next we could probably estimate some of those effects… vibration though is largely a sophisticated guess.