Newbie pitch
 

So I am new to the eco-modding forums, and I have a pitch.

Essentially The largest problem with ICE is that 60% of your converted power leaves the engine unused. Actually, this is the problem with all engines, you lose power somewhere you don't mean to. Unfortunately there is no beautiful mechanical method to scavenge this heat energy that goes out the tailpipe and off the engine block, otherwise we would probably have it OEM.

This is where the hybrids come in. Hybrids are more efficient because they are capable of reclaiming energy in places that ICE cannot. For instance there is virtually no way to reclaim power out of braking in an ICE, but hybrids can do it just fine. Ultimately hybrids are more efficient because they are designed with less aggressive engines and fuel maps to conserve fuel rather ego. Also mechanisms for turbocompounding are not very effective because of complicated gearing that must go into connecting a turbine from the exhaust to the drive shaft.

A possible solution exists, not that its good or feasible, but its there. An old engine given a new chassis and guts has become the hottest new toy in commercial energy production, The Stirling. Stirling Energy Systems(SES <http://www.stirlingenergy.com/>) has manufactured a stirling engine that comes close to its ideal max. You can look at their system but in the short they take 700 degrees from focused sunlight and produce electricity through the stirling engine.

Its just under the size for a 400cc engine to produce their "25 KW"(33 horsepower), which is impressive considering my 1.5 outputs a weak 101 in comparison(good for fuel economy but weak because equivalently sized stirlings could crank 130 hps). Like a true carnot engine the stirling takes a long time to spool up and respond to temperature change(unlike your gas pedal) so its out to juse burn gas and let the stirling take over.

To the proposal.

Rip out the trans(saving some energy from mechanical losses and heat), route the engine shaft into a generator(losing some energy to conversion(heat, magnetic fields, blah, blah) powering your car with two electric motors half the horsepower of your original(smaller engines attached directly to the wheel evade drive shafts and their associated weights and energy losses(or four engines 1/4 original horsepower)). Attach Stirling engines downstream along the exhaust pipe(not the same size as the 4x95cc SES, probably smaller and 3-4 of them) and after the initial spool up of the stirlings you recover nearly 60% of the energy your burned gasoline gives off instead of sub 30% in standard ICE. A problem yet unsolved by mechanical means is how to reclaim or prevent losses while at idle. Unless the engine is cut off it is wasting enormous amounts of energy(virtually all of it, excluding any energy converted for headlights or brakes). Also it avoids the expensive and heavy hybrid batteries. Instead of 500 lbs of batteries just add one or two to the trunk to reclaim solar, braking and idling electricity.

Obvious downsides
removed parts will not outweigh stirlings, generator assembly and batteries.
Minimal if any economy gain for the initial spool up time
Probably more that I've thought of but its late and I'm tired(I'm sure there are plenty I haven't thought of and will soon hear).

Bonuses
Could drop engine size for improved fuel economy because the stirlings would boost HP after they warmed up on the hotside(however long it takes your car's exhaust pipe to burn you)
Could recover electricity from regenerative braking and solar if your car is parked during the day.
Could remove components of the car that are heavy, expensive and break.
Instead of having complicated CV joints for FWD could use less complex more reliable(comfortable) joints since the power could be generated on the other side of the joint.
All ICE improvements to efficiency are added bonuses i.e. HCCI, turbocharging, lean burn
Does not involve an enormous increase in weight for hybrid batteries,fuel cells or "weighty" objects
Could jump overall car efficiency from 30% to 60%.

Hello,

There are internal combustion engines that are 2X as efficient (~39.5%): Revetec Homepage

Revetec trilobate engine

After reading through the trilobate forum, and some(didn't have time for all the revetech page this morning) It seems like the X bloc idea has advantages. However, it also seems that having a much more efficient ICE does not really affect the above proposal. The trilobate would reduce heat soak through the engine block because its not causing greater friction to get the power out of the cylinders. Also it seems it's going to save heat soaking simply in the two stroke fashion, because the metal can only absorb so much heat so quickly.

That said as long as the exhaust is hot, and I do suspect it would be even after being sprayed(or line the stirlings up first and insulate the pipes to avoid heat exchange with anything other than the stirlings put the (NO)X spray on the otherside and give it a run) and the stirlings would still have a scavenging ability.

<edit>
Engine output with 40% efficiency out of the engine would still put 30-40% out the tailpipe and 20-30% radiated from the bloc itself.
If you can recover even 20% of either(or both!) you gain a 50% fuel economy boost. Even if ICE gets to 50%, you could still recover 25% of the lost heat and gain a 50% boost in economy and still be well under what stirling engines are capable of today.

I think it's a great idea! Of course, I thought it was great when I had it, 4 or 5 years ago :-) And it was great when GM had it, back it the late '60s/early '70s - do a search on "StirLec".

The problem is that in the past Detroit could always get by by slapping new sheet metal on old bodies - whether it's tailfins or a station wagon on a truck chassis - and spending a bunch of money on marketing.

I knew I wouldn't have been the first(obviously I'm not even the first here, oh well).

But the more I consider this idea the better it gets. Using electric motors attached directly to the wheel you evade, axles(why not just use the frame, doesn't have to carry mechanical action anymore), differentials and engine piping or whatever can flow unimpeded by the drivetrain components.

Not that those components really weigh a ton(although both axles combined would by far more than some of the "hair-splitters" posted here, like removing windshield wipers), but they do steal substantial percentages of engine power in their uniform acceleration as well as any and all translation points where power would be lost to heat and grinding.

Although, I said solar would be helpful. . .If I coated the entire top of my car in solar panels I could get maybe 1 horsepower. . .for 900 bucks. Thats not worth it(unless I'm piggy-backing a steady tractor-trailer and still getting sun). Although, If you were going to do it, you couldn't really hurt anything scavenging more electricity.

I'm stuck sitting on my hands because I can in no way manufacture a stirling light enough and efficient enough to package somewhere along the exhaust that would make reasonable power gains.

James I tend to agree, but most of the people on here don't think like detroit. I would imagine we are all in the aptera crowd lol.

But when that vehicle is already available and gets ridiculous gas mileage why compete. Maybe since SES and Aptera are both Ca. corporations they would get together and boost the Aptera hybrid to something even more ridiculous like 500 mpg. . .

I could drive for weeks on a gallon(I only drive 2-3 mi a day lol)

It also allows you(if you're running it in the city) to stay in the low range rpms of the ICE where you achieve greater fuel economy anyway(bad news for HP-types). For that matter. . .you could just run the engine at its peak power/fuel consumption rpm most of the time and vary how much load you pull from it(not really all the time but way more often than we can with current setups).

My question is: How much do you think a transmission and driveshafts weigh? At a ballpark, figure 75 lbs for a small-ish car like my CRX or a similar-year Civic.

Now, add two hub motors. What do those weigh? I'd guess more than 25 lbs each. You will need batteries to hold the electrical power you are generating. Maybe not as much as a hybrid uses, but probably not a lot less. Figure (going small) 50 lbs for batteries. And how much does a Sterling engine weigh? I don't know, but even if you get one at 10 lbs, you still need the cooling system (which adds weight, a small one might be 10 lbs?), and an alternator (which also adds at least a couple of lbs).

So you have added some waste energy recovery, but at the expense of quite a bit of extra weight. It would be very interesting to see what kind of trade-offs would be involved.

You could downsize the ICE, which would reduce the weight some more. Or you could eliminate it all together, like what was done by GM many years ago or Dean Kamen more recently...

Interesting ideas, though.

-soD

-soD(is it ok if I use the acronym to reference you?. . .its alot shorter lol)
You're right I know for a fact you would be adding weight. I assumed you would be essentially adding a secondary engine(in the case when the ICE is not downsized). So it would be a substantial amount of weight.

The SES suncatcher employs a system that is smaller than a 400cc engine. Weight wise who knows? I don't. The parts could conceivably be made from aluminum and then it would be light(lighter than a block of steel. . .) Bonus point no cooling system required(although 10lbs is way under what the stirling would weigh). The engine could be. . .Aspirated?. . .naturally because the engine's system is based off heat difference and heat syncs on open air and even more effectively when exposed to wind created by driving.

To the point, the 400 CC produces 25 KW(33 HP).

Drop Trans 10 lbs additional 10-15% efficiency gain(mechanics of trans are not FE)
Drop Axles 20 lbs additional boost, no wasted uniform acceleration
Drop differentials(front or rear or both depending on car) 10 lbs additional friction gains
Drop CV joints(FWD+AWD only) 2 lbs additional friction gains

These are underestimates. I'm pretty sure the components weigh more so I tried to low ball since I don't have actual numbers(the trans power loss depends on your model but its legitimate).

Add
2(4) engines 50(total or 75ish for four) pounds 5% energy loss in conversion(electric to mechanic)
2 stirling engines 70 pounds 1/4 recovery of lost energy(efficiency of 25%(actual are up to 68% and av is 50%))
1 larger alternator 20 pounds more than old alternator 5% loss in conversion(mechanical-electric)
2 standard batteries 80 lbs

let's assume my Del Sol is the test car.
dropped 42 lbs and gained 200
+158 lbs
added (1/4 of energy input to stirlings(100 hp)) 25 HP
The formula is 1-2% for every 100 lbs(?) so 4%(high-side)
101 hp +25 hp =125 HP
25/101 ~ 25%
25%-4%=21% increase

Gain of 6.5 mpg

This ignores that the alternator, electric motor and electrical wiring is more efficient than. . .Trans, Drive shaft, Axle, Differentials, and finally joints.

a negligible amount of power is lost in the cables and the overall % lost through the conversions would be 10%(equal to the trans of a manual alone).

this also does not account for energy stored in the batteries when coasting(engine on) or traffic stops(engine on). The batteries could come in to play here and get the car through the energy expensive acceleration phase and recharge off the idle and regenerative braking.

Ignoring energy saved in the bats or friction savings if you bump to 50%(17-19% behind SES) my del sol jumps to 52.5 MPG(50% increase). Even the Prius, Camry and other hybrids don't come close lagging 6 mpg behind.

Somehow the Aptera still beats it(I suppose they are doing something similar but with a much lighter vehicle(1500 lbs opposed to 500) better aero frame(drag of only .011 .11 whichever is amazing but not unreasonable(can't remember where the decimal goes ^_^)) and probably is using smaller motors than an equivalent 100 horses.

If you really really wanted to get picky about it. . .drop the aluminum,steel whatever shell you have replace everything with carbon fiber(frame of titanium or aluminum) put 13-14 inch tires on, replace the glass, take out everything that is not drive essential, drop engines to 100hp aluminum engine, add a stirling on the engine block to salvage that other 20-30% sneaking off the block and you could find yourself in Aptera land without the extra batteries or three wheels.

Couple of things to think about:

Wheel motors, unless they're awfully light, add considerably to unsprung weight. There'd be other problems too, if doing a conversion. For instance, what do you do if you get a flat? Whereas if you just bolt on an electric motor where your transmission sits now, things are much simpler.

Solar panels on your car = bad idea, at least until they become about as cheap as paint. Your car's going to spend a lot of time in the shade, or parked/driven at non-optimum orientations to the sun, so you'll get much less than their max potential energy from them. Better to leave the solar cells sitting on your roof at home, pumping out watts whenever they can.

I agree on the solar thing, but if you were really going to push the envelope its a step(and some manufacturers claim to be getting close to the paint).

It's more simple to swap out the trans for an EM, but then you still have to spin an axle thats 4-5 feet long and several inches in diameter. And the EM's could attach to the wheel the same way your axle does, through the lug nuts. Put it up on a floor jack pop the tire off and screw the heads down tire changed. same as it is now.

The unsprung issue I had considered but had not resolved, and in light of presenting the best argument did not bring it up. I think it was yokohama that was designing a wheel that was not inflated but ran alot like the lunar landers piano wire mesh(although it was aluminum slides). It would allow for the same deflection the rubber tire would give and have a much greater life span. Use the same concept just use thinner sheets or more flexible alloy to give greater deflection to protect the motors. Or combine the two standard tires and the non-rubber part(steel, aluminum, whatever) wheel would have additional flexibility to add deflection.

Or just straight up use rugged motors to start with.

Another plus about the wheels attached to a very short shaft and then the motor is if anyone of them failed the car could easily still reach its destination. It may even be possible for three of the motors to fail and still be able to limp to a service station. If the ICE gave out you would still have some very tiny amount of time stored in the thermal energy in the pipes and chassis around the stirlings and your three total batteries to juice you a very short range(maybe around a few corners into cell range).

Huh? What sort of car do you plan on converting? Two half-shafts an inch or so in diameter and a couple of feet long on anything I've owned recently. Even in old rear-wheel drive, solid axle setups the shaft that actually spins isn't all that thick.

Of course you have the CVJ/DOJ on each end, but you would need something similar if you were going to attach an electric motor to the wheel via a shaft. I think what I'm trying to say is that you've already got a well-engineered & tested transmission-to-wheel connection, so why re-invent it when the gains seem likely to be marginal? You can (I think) buy suitable motors & adaptors pretty much off-the-shelf, so why not do that, and invest your time & money in getting the Stirling engine part to work.

If we could just change hydrocarbons into electrons directly.

Wouldn't that be awesome... but we can't... so ideas like this are the next best things... I'm throwing my personal support toward the OP for the idea, now lets see some sort of implementation?

And thats where the problem comes in(Christ), I have a neighbor who managed to build a functioning stirling engine that is pretty fantastic(considering its home-made from scratch) but its not anywhere near being able to produce 25 hp off my exhaust. Although it is light(less than 10lbs). So it may be possible to stack them in series. Although. . .not on my car. The Del Sol if anyone else owns one has a very cramped engine bay and adding a cubic foot box somewhere. . . Of course I could rip out the cooling fans(since my car never gets hot enough to use them(un-FE she has a wide open grille that is not stock and I've done a few things to improve air flow to keep the fans off)). Would have to shield the engine thermally to trap as much heat against the stirlings as possible while venting cold air to the cold side without heat soaking from the radiator(or freezing the hotside or the engine)

Ok James I'll stand corrected on the axles for sure. Sorry. You wouldn't neccessarily still have to use the CV's. . .Power doesn't necessarily HAVE to flow through them. . .

Wheel-Emotor-pivots-chassis. motion does not have to pass through a joint(making the joint cheaper and the drive more efficient). I'm not sure what this would do to the engine itself but if it were light enough it wouldn't drastically change the unsprung car weight. . .(I think assuming we are popping things off that are also unsprung?).

There actually isn't too much about the unsprung sections of a car that would be changed doing the emotor per wheel thing... there is a company out there that makes kits for Minis already.

IIRC, they have kits that have the same HP as the ICE engine does PER WHEEL, thus making your Mini a 600HP monster with no lagtime waiting for torque to build up or a turbo to spool.

Nicest thing I've ever found about E-Motors is that their torque rating is at 0 RPM. They don't need to be spun up to have torque, since they aren't fuel based. The electrical current can be just as strong at 1rpm as it is at 1200 rpm.

It'd be great to have torque on demand.

Linky: Electric Mini: 0-60 in 4 Seconds: It Has Motors In Its Wheels : TreeHugger

Yeah I hadn't actually considered the better torque stability, but that would also be a plus.

I got to thinking and it may be the best idea(key operator = may) to insulate the exhaust pipes. With asbestos. . .or since its the 21st century how about mylar and some pink fuzzy coated in flame retardent spray and maybe a very thin aluminum shield(also doubles to bring the underside of the car to lowest drag possible(and then I can wax it. . .)). But if that were done I could route the pipes into part of the trunk(where the spare goes) and put a stirling there. would just have to mount it inline and pipe air from outside in the same gap and then out the same gap(through separate pipes same hole).

Obviously its more beneficial for the engines to be mounted up front for increased traction(FWD) and the heat would not dissipate, but thats asking to get alot of room out of my engine bay only removing a trans and both cooling fans.

I will definitely be going to visit my family over thanksgiving and my neighbor with the engine to check and see exactly what kind of HP and weight. . .

I don't know about most other cars, but I know on my Honda, I can actually grab the muffler for a short period of time before it feels like it's burning... which means it's not that hot, compared to other sections of the pipe.

Believe it or not, one of the greatest areas of potential heat loss due to convection is the catalytic convertor... hence the reason there's a heat shield on it... it's always in close quarters to flammable materials.

If I still had my Delta 88, I could show you what happens when the cat is too close to the body and overheats. The floor of the car actually caught on fire... burned most of the driver's side carpet and underlayment, but I put it out before it seriously damaged anything. The car was idling in my driveway when it happened, running richer than ever.

Rich mixtures heat up the cat... lean mixtures cause parts of the engine to overheat... I won't go into detail on that.

Anyway, have you ever considered driving a sterling with the pressure from the exhaust, rather the heat? Or even using both... recapturing even more energy. Don't forget, part of the waste of the engine is in the pressure exhausted. (It takes energy to create the pressure, therefore exhausting the pressure without using it is a waste of energy.)

I had considered harnessing the expansion that causes the pressure, but at the same time I am hesitant to consider it. I'll get to it in a second.

The most opportune place is the hottest place for a stirling to run and thats right out the block, but I probably at best would only be able to get one small unit at that location right now. Insulating everything would be advantageous if you wanted to take advantage of trunk space and put them there for ease of access and mounting.My muffler usually takes a bit of time to get hot but once it does it's scorching. I burned myself rather badly just leaning into my trunk before I realized my leg was touching the muffler. . . it protrudes slightly.

To the pressure/expansion/turbulence. . . I considered it but I'm not certain it actually saves you energy. It would be like running a turbo or supercharger. You can gain more power but it comes at the cost of the engine having to fight the backpressure. In the case of the turbo you typically lose fuel economy(efficiency typically means power/weight and thats always a gain in the case of more air and fuel in the engine). The reason economy usually goes down is because the engine, standard ecu, will inject more fuel to match the greater airflow. Usually this exacerbates the normal inefficiencies, rubbing two pieces of metal together wears them down and rubbing them faster usually has an inceased effect kind of thing.

All that said I tend to lean away from the turbo and towards heat recovery because the kinetic energy of the air from the exhaust is not immense, but creating back-pressure is a huge problem for the engine. The Stirling would cause the air to become more dense and slow down but not enough to cause a measurable backpressure.

Another point of consideration would be creating ramscoops for the stirling cold-sides. the colder the air, or the more cold air, you can get the faster, or more heat you can convert to motion. Effectively the stirling could become much more efficient at highway speeds since it follows carnot ideals rather closely((700-430)/750 or (700-343)/700 degrees input-output/input in kelvins).

Turbo chargers don't add that much backpressure to the exhaust stream.. Granted, it's measurable, but after installing a turbo, you can almost run a resonated straight pipe to exhaust the engine, therefore you lose the backpressure of a muffler, and it's not harshly loud in the lower ranges.

Anyway, good enough reasoning, but I was thinking something more like venting SOME of the pressure from the exhaust, like where air-pumps used to pipe into cat convertors... take that pipe, and use it's exhaust pressure to drive the sterling, instead of blocking the entire exhaust flow.

One could add several of those pipes to use the pressure instead of heat, and they could be mounted just about anywhere, since you'd be connecting them with pipes.

They'd be decreasingly efficient the longer those pipes were, and the further from the point of exhaust, but it might present another option to reclaim some energy.

I'm more than a little puzzled here. You're talking about adding a Stirling engine to the exhaust of a conventional IC engine, but having that drive a generator which (with batteries) drives the wheel motors (or other electric propulsion). Aren't you getting more than a bit Rube Goldbergish? Why not cut out the IC, and have the Stirling drive a generator which extends the range of your plug-in hybrid?

The battery wouldn't even have to be that large, say enough for 5-10 minutes of driving while the SE comes on-line, so you save on weight & cost.

Mean while, what drives the sterling motor? It has to have a source of energy, unless you're channeling battery heat into it, which would work out great, since you have to vent your lead-acid batteries anyway.

That might be a consideration, to reclaim some battery heat as energy to help recharge the batteries or something, which would still cut out the ICE altogether.

The Mini kit uses an ICE also, just an extremely small one that kicks on when the batteries start to lose power, and it only powers a generator which charges the batteries again while you're driving. In that case, something to reclaim energy from the heat lost through the exhaust would be great.

Interesting idea James, but Chris posted first so he gets first response.

I see what you are saying. It's definitely worth testing. It's hard to find numbers on the backpressure inefficiency problem because most people who are putting turbos on don't like to talk about how its a bad idea or even the downsides(read OFF COURSE ITS A GOOD IDEA HOW COULD IT BE STUPID). And venting it off like most Catback systems use dual exhaust to avoid jamming the flow while venting any extra is an even better idea.

It could be done to just have the SE run the gen and bats. The issue with SE's though is they don't respond to changes very quickly at all. An SE capable of 100 hp would take like you said 5-10 minutes to respond to any kind of throttle change. So the engine has two options either output average power for driving(30-40) or output enough power for maximum driving(55-60 mph). If A is chosen I'd be fine in town but as soon as I hit a road thats 55 or the interstate I'm going to be draining those batteries rather quickly and its going to take at least another 5 minutes for the engine to respond to the amped up heat. Any time in either mode you are not doing 40 or 60 it's like holding the clutch in partially and revving it to 3,000 when you only really need 2,500.

That said using the SE in either mode would be more efficient than the ICE(IC=40% on a good day SE=65% on a good day). The reason for using the ICE still is it would allow for a dampening of the SE's problems. During the time the SE is spooling up. . .it's not even moving for about a minute and definitely not generating any power so you have to let the car idle for 5 minutes in the driveway. Any time you change speed you throw away five minutes of heat it won't recognize. It's not being entirely thrown away but for the first 2 1/2 minutes it's just washing across the plate with no effect.

The ICE let's you. . . modulate that a little. So you can change speeds and start off your car without losing as much energy. It's like using a diode in an AC circuit and then throwing in a capacitor. the diode shows a half wave form and you get no energy half the time with the capacitor you get nearly constant voltage. With the ICE you constantly get above 30% and when the SE is in sync you get much better, instead of starting at 0% and climbing to 60%.

And the weight of the engine is not so terrible its heartbreaking. Even if we call it 400 lbs for my 1.5 engine. . .I don't mind considering this would be like doubling your standard gas mileage or better.

A burner, of course. Something like the burner from a home oil furnace, heating the hot side of the SE directly.

Another point to keep in mind here is that SEs are heat engines, and so the amount of power they can produce is governed by the temperature difference between hot & cold sides. (Basic thermodynamics, IOW.) You're going to be able to get the hot side hotter with a burner than just by running IC exhaust over it.

For the startup time issue, that's why you have the batteries. Your minimum battery requirement is whatever lets you to drive long enough for your SE to get up to speed, though of course if cost & weight allow, you can add more to add more plug-in electric range.

Hm. It seems like a half decent theory, but after re-reading most of this, I don't think it will be very practicable... (note, not practical, practicable... two diff words.)

I'd still like to see OP have a go at it, but I'm not sure what the feasibility will actually be comparing to the work put in, vs the energy actually saved.

Obviously, anything is better than nothing, but if the ROI isn't there, it just can't be justified.

You're dead straight on the SE principle, bigger difference more juice. You're still also dead straight that the SE burner alone would be greater(I agreed with you a post back) than the ICE.

The only issue I take with it is with the SE only you burn 5-10 minutes of fuel at 0 mpg. True you are moving but as far as the SE is concerned you are doing 0 mpg.

True also that you would get greater power with an SE burner.

But you still lose out because you either have to produce more energy than you use(to avoid having to heat the engine more to get to a higher speed) or you have to toss another 5 minutes worth of fuel at very low mpg to get up to that speed.

Yes the batteries could overcome the problem, but why waste fuel? Running it off ICE exhaust it will generate less overall power (modularly) but the amount its not generating the ICE is off fuel that would have been wasted for the first five minutes.

The reason to employ the ICE-SE combo is to achieve a smooth power delivery curve that's maximized for efficiency

I attached a paint image I sketched very quickly(and horrifically).
Blue is the ICE by itself
Red is the SE by itself
Purple is the ICE-SE.
The initial red trails blue because it takes the ICE less time to achieve 30%(almost instantly, but it takes it time to climb to optimum around 34-35).
The purple matches the blue exactly(it would actually be marginally higher) because at that point its operating just the ICE(the SE's are still warming).
Then purple and Red diverge from Blue because ICE maxes out at 35%.
The dip is presumeably an increase in speed where the stirling loses substantial FE but the ICE-SE still has the ICE dampening the loss. the Blue ICE line does not suffer noteably.

The graph assumes a constant speed with no interruptions otherwise you have more dips for the Red and Purple with the same effects. If the speed is variable above 10 mph the Red(SE) line will tank below the purple(ICE-SE) line.

Theoretically you could get almost 100% efficiency. But. . .You'd have to have 50-100 SE's to get that last 30%(which is why the best Gas turbine engines weigh several tonnes and still only get 70%).

But Yeah GE does this already. They use the Gas Turbine(GT here forward) to supply immediate demands, like hospital goes down and they need power, but they don't want to have to run the GT full throttle to keep that up so after several minutes the GT spools down as the other systems catch up.

Question:

Given the latest bits of information, I must ask if anyone has considered the RPM at which the sterling would run, and the rpm/work needed to drive the generator circuit?

Are we driving one generator with several SE, or are we driving generator per SE?

I'm thinking that even a 30HP SE is only going 100RPM or so (that might be wrong, probably is, so the math here isn't necessarily correct either, other than analytically.)

If it's generating 30HP of work at 100RPM, and the generator needs to spin at 3000 RPM to make any reasonable amount of power, the reduction would be 30:1 (30 at the generator for every 1 at the SE) Which means that the generator would only see 1/30 of the HP that the SE is giving.

1 HP may not be enough to drive the generator to the 3000 RPM it needs to see with the kind of load it's going to be creating while charging the batteries/electrical system.

Granted, more than one system like this would lessen the load, and technically, you could employ enough systems to lessen the load to the extent that 1HP would be sufficient, but how much weight would you be adding at that point?

It seems kind of counter-intuitive unless the efficiency marks go up significantly for each piece of the puzzle.

That's what I'm thinking, please tell me I'm wrong. I'd hate to see this project wasted over something so consequential.

Um, no the engine would not have to run at 3,000. that's around their free-wheel speed. and to counteract the SE having very low torque, we just make the generator inclined for small torque(fewer coils).

Engines of this nature already power the SES Suncatcher in site 1 and site 2(under construction not sure if they have started erecting units yet). They run very low torque and very high RPM at 711 degrees C. This engine would run reasonably high rpm at 1000-1500 and low torque as well providing less HP(less than 33). keep in mind the suncatchers are employed in the desert for maximum sun, but they also have a very high background temperature(well over 100 for the 25 KW tests) and my avg temperature in the summer is less than 80 and the temperature in the winter is 30-40. So at both of those times I start off with an advantage because my engines will be much more capable of heat syncing on open air than theirs as well as a moderate temp difference(theirs is 700-120=580 mine would be ~400-60=340)=(20 hp not including increased heat syncing on cold side due to car speed or lower atmospheric temperatures.)

So roughly 20 HP for 50-60 lbs? What are the 5th wheel guys talking about? increased rolling resistance and huge amounts of weight for how many horsepowers? Also they aren't stripping out trans or several other weight contributors.

So that sterling engine would be outputting 115.5 lbft of torque @ 1500 RPM?

115.5 LBFT x 1500 RPM = 173250

173250/5252 = 32.9 HP

Or for your estimate, about 70 lb ft.

70 LBFT x 1500 RPM = 105000

105000/5252 = 19.9 HP.

Most car alternators, and welding apparatus generators, are built to create max output at a given RPM range, I believe most car alternators peak at about 3000-4000 RPM, which is why I used that for a figure.

Ah I understand. I had the total intention of using a car alternator but pulling some winds out of it for lower torque. I would have to adjust it for the lower RPM as well. It might actually serve better to use a Windmill (Wind turbine) alt instead because they are rated for lower RPM and just pop some of the winds out of it instead.

OK, now we're on the same page... are those HP/TQ figures right?

That seems like quite a lot for a small 1 cylinder heat driven engine.

Who said it was 1 cylinder? ^_^

Also the advantage of the Stirling cycle. . .there is no combustion. No thick steel or thick aluminum or heavy duty moving metal parts.

Moving metal parts yes but not necessarily heavy. Everything about the Stirling can be designed to be lightweight since it has to just be air-tight(opposed to being air tight and and being able to withstand a high pressure detonation).

The theoretical figures are correct. I'm not expecting to see those though. SES can get them but they spend lots of money and have automated systems that manufacture every single piece to within thousandths if not less of spec.

I'm expecting around twenty pounds and half that in horses.

The output for the Stirling is the cold side(air temp) and therefore the hot side can be used for engines further down the line. Of course you'll get less juice out of each of them but 100 lbs = 50 HP = 50% increase in FE. second most important 100 lbs in the car.

OK, now I'm starting to see this coming to something.

As you can tell, I'm not very familiar with the SE, other than seeing them in science classes and such.

Now, when you give me numbers, I can make the correlation... fact is, if you can get 50 HP for 100 lbs, you're doing better in overall efficiency (HP:weight) than the ICE is, in most cases.

Honda D-series engine weighs in at 270lbs (average, wet) and produces a mere 90HP (again, average.)

270:90
30:10
3:1 vs. ~2:1 for the SE.. not bad.

Their power-to-weight is not great. its actually terrible. Gas engines can get 1.0+ and diesels can come in at 1.2 and Gas turbines come in very nicely at 1.5 and higher. Scramjet engines do. . .like 50:1.
But in this situation(low power) Stirling comes in better because it does not have ti withstand detonation and the ICE does. Stirling just has to be able to withstand heat differences and high temperatures(400-800). can make them out of very thin aluminum or very thin pretty much anything heat conducive and resilient.

<edit> scramjets are just gas turbines. . .sort of. . .more like pulse engines. . .but anyway they only work at the sound barrier and faster because they ramscoop air into the manifold to achieve ridiculous intake pressure blast lots of fuel in ignite and the really high pressure acts as a barrier to keep it travelling backwards while the exhaust manifold is just a wide open cone(the pressure against the cone wall causes the acceleration). its like two big traffic cones put together with the small ends together and the fuel is ignited at the junction. vessel goes rocketing on at mach 15 or so.
</edit>

Actually knew that much about scramjets... not too much more.

lol. . . they are entirely the opposite of FE. They burn fuel in ratios of gallons per second opposed to gallons per mile or minute or miles per gallon.
Although you can go from New York to BaghdaD in 30 minutes. . .

Forgive the side-tracking, but I need to point out the above statement is incorrect. When you use gear reduction (and pulley reduction is just a different type of gear reduction), you still transmit all of the power. The torque is what gets multiplied by the gear ratios, as well as the RPM. But the power stays the same.

-soD

HP is a relative number derived from TQ...

To calculate HP: (TQxRPM)/5252=HP

That said, if torque is multiplied or divided, as the case may be, so is HP.

If an engine has 100 LBFT of torque at 1000 RPM,

100x1000 = 100000
100000/5252 = 19 (horsepower @ 1000RPM)

What you're saying is taking the speed of the driven object and deriving horsepower from it.

Example

10 LBFT @ accessory pulley, 10000 RPM (10:1 from engine)

10 x 10000 = 100000

100000/5252 = 19HP

At least from what I remember of physical science in HS, that's correct.

well, if you mean you want to gear it up(speed increase(torque reducer)) the biggest one I've ever seen is a 5:1. I don't think you can possibly get them higher than that.

I am not very familiar with the above formula's but I know the base unit for horsepower(definition) is its the ability to move 500 lbs one foot in one second.

Although. . .the above definition sounds legitimate.

I think the mishapy may have come in at the computing it for the output. The formula seems competent to derive horsepower from the engine but it seems like you just didn't multiply the output of the gear pulley by 30,000 instead of just 1,000.

i.e. you said it sees 1/30th of the power the engine produces and by that I think you mean torque. True per rpm it sees 1/30th of the torque. . .but it also sees 30x more RPMs. in using a gear assembly to change the speed/torque you effectively multiply by one because if your formulae holds you aren't changing the numerator(its torque times rpm) so if you decrease one in the pulleys you automatically increase the other. If its an ideal pulley. realistically most of it gets through but you lose some to friction and gear grinding.

OK, I messed up last night.

The second formula is false, the 1st and third are true...

Basically, regardless of the torque figure, when all things are equal, the same HP measurement can be taken at the drive side, or the driven side, less frictional losses.

I read up a little bit again last night on that math in one of my old science books.

soD, you were right about that. My apologies.

Edited post accordingly.