By on March 4, 2014

2014 Porsche Motorsport- Porsche 919 Hybrid- Angle

The problem with battery electric and fuel cell cars is gasoline. Petrol is genuinely a superior fuel, at least in terms of energy. It has so much energy per gallon, 116,000 btu/gal, that we can use it in an engine whose theoretical maximum efficiency is only 37%. That means that with all the gizmos a modern gasoline powered internal combustion engine has that increase fuel economy, still two thirds or more of the energy in the fuel is being turned into unusable heat, not motive force.

 

Even with all that waste it still is a more practical powerplant than using batteries or other alternatives. It’s long occurred to me that in addition to improving the efficiency of the engine itself, recovering energy from that waste heat might be a productive way of improving the overall efficiency of the car. Porsche is returning to international endurance sports car racing this year with the 919 that they plan on racing at LeMans, and as part of its hybrid system it incorporates a device that in fact generates electricity from the heat in the exhaust, recovering energy from what would normally be waste heat.

Porsche isn’t the first car company to look into recovering waste heat. In 2005 BMW announced their “TurboSteamer” test bed concept that they said gave 10-15% improvements in fuel economy and power. The TurboSteamer integrated a series of sophisticated (and probably very expensive) heat exchangers into the exhaust and cooling systems to power a two stage Rankin cycle engine that assisted the internal combustion engine. A second generation TurboSteamer was announced in 2011. By then BMW had succeeded in miniaturizing the components enough to fit in the standard packaging of a 5 Series sedan.

2014 Porsche Motorsport- Porsche 919 Hybrid- Technical Drawing- Engine

One difference between turbochargers and superchargers is that superchargers are mechanically driven by the engine while turbos’ turbines are driven by the pressure and heat energy in the waste gases that are the product of combustion. For that reason, turbocharged engines have greater thermal efficiency than normally aspirated motors. The Porsche 919’s hybrid drive puts a new spin on recovering energy from exhaust gases with turbine devices. The 919’s V4 engine does have a conventional exhaust driven turbocharger, but it has another exhaust driven device that’s part of the race car’s hybrid drive. The 919 is a through-the-road 4WD hybrid. In other words, it has gasoline power driving the rear axle and electric power that can power the front axle on demand. The batteries for the electric motor are charged by two different systems. One is Porsche’s “conventional” KERS-like system that’s used in the 918 Spyder supercar which is essentially a regenerative braking setup. Porsche’s describes the other source of electrons as “a system that recovers thermal energy from exhaust gases via an electric generator driven by the exhaust gas stream.”

2014 Porsche Motorsport- Porsche 919 Hybrid- Technical Drawing- Hybrid System

What that sounds like is that instead of driving an impeller that pressurizes the fuel/air charge, as a conventional turbocharger does, Porsche’s “fundamentally new” device is an exhaust gas driven turbine that spins a generator. In a sense it’s a reversed setup for an electrically driven supercharger. Instead of a belt drive running off the engine, an electrically driven supercharger uses an electric motor to pressurize the induction. Porsche apparently did the equivalent of flipping one of those around and mounting it on the exhaust system.

We’ll probably seem more efforts, for both racing and road cars, to turn that 63% or more of the energy that’s currently waste heat into usable power. Turbocharging guru Gale Banks, who knows a thing or two about using waste heat energy, recently said on The Smoking Tire’s podcast that he was hopeful that engine waste heat could be recovered by large scale Peltier devices. Peltier devices are what heat and cool your drink in heated and cooled cupholders. They’re very interesting electronic heat exchangers. If you apply DC voltage, one side will heat relative to ambient temperature and the other side will cool. Reverse the polarity and hot and cold change sides. Fortunately, like piezoelectric devices, the entire process is reversible. If you make one side of a Peltier device hot and the other side cold, it will start generating electricity, something called the Seebeck effect. The term Thermo Electric Generator, or TEG, has been coined for devices that use the thermoelectric effect to make power.

Banks hope may actually see the light of day. Purdue professor Xianfan Xu is indeed heading a research team that is developing large scale Peltier devices designed to work with the temperature differentials one finds in a typical car engine and exhaust. BMW is also working on TEGs in addition to their work on the TurboSteamer concept.

Porsche isn’t saying just how many kilowatts their exhaust driven generator puts out, but it’s safe to assume that the power it harvests is worth the weight it adds to the race car or it wouldn’t be there. Race cars may use technologies that are not yet economically practical, but the engineers who design and build them aren’t going to use something that is a net energy loss.

Source: Porsche

Ronnie Schreiber edits Cars In Depth, a realistic perspective on cars & car culture and the original 3D car site. If you found this post worthwhile, you can get a parallax view at Cars In Depth. If the 3D thing freaks you out, don’t worry, all the photo and video players in use at the site have mono options. Thanks for reading – RJS

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61 Comments on “Porsche 919 Hybrid LeMans Racer Goes After The Two Thirds of Gasoline’s Energy That’s Wasted As Heat...”


  • avatar
    bunkie

    I’ve long been interested in this subject. Going back even further, there was a fascinating article in Kitplanes magazine a few years back that covered the turbo-compounding used in various aircraft engines during WWII. In essence, the turbo drives a shaft that supplies mechanical energy back to the crankshaft. What was fascinating was the detailed graphs that showed how much heat energy was recovered (which, if memory serves, was somewhere around 20%). Of course, such a solution lends itself to aircraft applications where power demand tends to be constant. When I read that article I was struck by the idea of driving an alternator off the turbocharger in a hybrid system.

    I’ll make a prediction: eventually all cars that have combustion engines will be some form of electric hybrid. There’s just too much energy loss to ignore. The resulting complexity will be mind-boggling to contemporary eyes, but it follows the natural progression that has been in place since the invention of the automobile.

  • avatar
    wmba

    ” … theoretical maximum efficiency is only 37%”

    You lost me there, Ronnie. What theory is that? Both Toyota and Honda gasoline engines in their hybrids are over 38% at their most economical right now.

    • 0 avatar

      Carnot cycle, or actually quite a bit worse… Mechanical engineer, huh? :)

      • 0 avatar
        henkdevries

        Carnot cycle, my dear sir is a bit of a short answer. I leave an option open for you to redeem yourself by elaborating on thermodynamics and enlighten this fine gentleman.

        Keep in mind that Toyota Hybrids have an ICE that employs the Atkinson cycle instead of the Otto cycle. In short the Atkinson cycle has an intake valve that is open longer reducing the compression ratio. With the expansion ratio kept equal more heat is converted into mechanical energy; efficiency rises. This comes at a price however; reduced power density.

      • 0 avatar
        wmba

        I think we’re talking Otto and/or Atkinson cycle here, agenthex. Also diesel. Perhaps if you know something useful, you could contribute.

        The Carnot cycle defines efficiency as the temperature difference between heat source and sink divided by the temp of the heat source. It is not real life, depending on gases acting in a perfect manner and adiabatic and isothermal compression and expansion. I am quite familiar with it, thanks.

        So, I repeat, what theory is Ronnie referencing that limits theoretical efficiency to 37%? Find me a reference.

        Large two stroke diesels like Wartsila in container ships are over 50%. So I’d like to know where this 37% figure came from. A perfectly reasonable request.

        • 0 avatar

          > Large two stroke diesels like Wartsila in container ships are over 50%. So I’d like to know where this 37% figure came from. A perfectly reasonable request.

          If you know how these things work is it really so hard to imagine with a gas vs. diesel engine (ie not same cycle nor stroke) designed to run at one speed? They’re easily 10% diff straight up. Does that answer your question?

          (since it’s possible you’ll get all semantic up in here, it’s technically less w/ same compression but that’s not really the point)

        • 0 avatar

          My general point was that a large amount of the fuel ends up as waste heat. I saw the figure 37% in a number of sources. Here’s one source that says it’s closer to 35% at the piston and as low as 15-20% efficient when power is measured at the wheels:
          http://courses.washington.edu/me341/oct22v2.htm

          • 0 avatar

            > I saw the figure 37% in a number of sources.

            Those are just practical estimates. wmba is just being an ass, or maybe he doesn’t know it’s an estimate either.

    • 0 avatar

      > You lost me there, Ronnie. What theory is that?

      Hey dude, since you’re so confused here’s an article with some theory:

      http://gredos.usal.es/jspui/bitstream/10366/19206/1/DFA_Theorical%20and%20simulated.pdf

      There’s even a bunch of links at the end for more info in case you don’t get it.

  • avatar
    mcs

    >> The problem with battery electric and fuel cell cars is gasoline.

    That may be true for PEM Fuel Cells, but SOFCs can use conventional hydrocarbon fuels.

    • 0 avatar
      Dr. Kenneth Noisewater

      Alas, they need to be about $0.10/W to be practical.

      I’d be curious to see how efficient a Miller cycle motor with electric supercharger on the intake and turbo generator(s) on the exhaust can get. Let alone a proper linear ‘free piston’ engine optimized for genset efficiency.

  • avatar

    > The Porsche 919′s hybrid drive puts a new spin on recovering energy from exhaust gases with turbine devices. The 919′s V4 engine does have a conventional exhaust driven turbocharger, but it has another exhaust driven device that’s part of the race car’s hybrid drive.

    That’s what they’re doing in F1 this year. Old KERS + hybrid turbo. It doesn’t really need “another exhaust driven device” since the motor couples directly onto the turbo which has the added benefit of maintaining boost w/ electricity.

    Winter testing is over and season starts soon; should be interesting.

    TEC’s to recover heat is neat, but I doubt it’s going to do much. Not much weight though so might be worth it anyway if they can get cost/complexity down.

  • avatar
    Sigivald

    “A turbo driving a motor” doesn’t sound like reclaiming *heat* energy to me.

    It’s using exhaust pressure energy.

    Which is a nitpick, but still; heat and moving air that’s being pumped by the engine’s exhaust stroke are *different things*, no matter what Porsche’s PR says.

    • 0 avatar

      > doesn’t sound like reclaiming *heat* energy to me. It’s using exhaust pressure energy.

      Is it, or is it using the heat/expansion of the gas to provide that mechanical work?

      • 0 avatar
        CRConrad

        @agenthex, @Sigivald: Seems to me that since the exhaust gas that escapes into the atmosphere at the end of it all is at the same pressure as the atmosphere, all the “exhaust pressure energy” that can be recovered from “the heat/expansion of the gas” has been recovered.

        But as long as the exhaust is significantly hotter than that atmosphere, I’d say they are *not* extracting all the *heat* energy, no.

        In sum, therefore, Sigivald’s “nitpick” is AFAICS correct.

        • 0 avatar

          > Seems to me that since the exhaust gas that escapes into the atmosphere at the end of it all is at the same pressure as the atmosphere, all the “exhaust pressure energy” that can be recovered from “the heat/expansion of the gas” has been recovered.

          So how do turbos inserted into the exhaust path ever work?

          • 0 avatar
            CRConrad

            By taking advantage of A) the fact that at that point in the path the exhaust gas is still expanding [Edit: or “trying” to expand], i.e. is at higher than atmospheric pressure; and perhaps B) because the exhaust gas is streaming through the exhaust pipe at considerable velocity, which gives it something that the engineers you’re so busy telling to Google stuff would probably call “momentum”.

            Why, are you still saying it’s just because it’s hot? If so, how many RPM did you get on that turbo in your fireplace? (Or electric oven, for that matter. Chuck it in there with your next batch of hipster sourdough loaves.)

          • 0 avatar

            I strongly recommend trying to grasp how gases work first before launching into crackpot theories:

            http://www.thetruthaboutcars.com/2014/03/porsche-919-hybrid-lemans-racer-goes-after-the-two-thirds-of-gasolines-energy-thats-wasted-as-heat/#comment-2961393

            > Why, are you still saying it’s just because it’s hot? If so, how many RPM did you get on that turbo in your fireplace?

            The reason why a fireplace doesn’t work well is because it’s design to ventilate to prevent the very thing (ie pressure) that makes turbos work. If you made a bunch of openings in the exhaust before the turbo it also wouldn’t work well.

    • 0 avatar
      krhodes1

      @Sigvald

      Turbos use primarily the heat energy of the exhaust, not the flow.

      Good write up here:

      http://www.thedodgegarage.com/turbo_fun.html

      The font choice and color leaves a lot to be desired, but he explains how it all works quite well.

    • 0 avatar
      krhodes1

      @Sigvald

      Turbos use heat energy, the mechanical flow is largely irrelevant. Here is a really good writeup on how they work:

      http://www.thedodgegarage.com/turbo_fun.html

      Ultimately, this is where the “free lunch” aspect of turbos come from, you get to use some of that heat that otherwise goes out the exhaust pipe.

      • 0 avatar
        krhodes1

        Weird – thought I lost this, posted again, and it showed back up!

        • 0 avatar

          redav> krhodes1′s link is not rigorously correct.

          For whatever reason I bothered to glance over this hideously typeset page, and in perspective your reply is argumentatively poor.

          As mentioned this is more of a technical classification issue rather than actual disagreement, and exacerbating this by reciting from the textbook is bad technique.

          More clearly stated there’s a bunch of energy the chemical process creates; some gets converted into the mechanicals and the rest of the hot stuff goes out the pipe, the latter of which we’re classifying. Whether you convert this into something more usable by confining it into a volume which gives it pressure to push more mechanicals or a “thermal flow” approach isn’t really cogent to the original point.

          That’s why Sigivald correctly calls it a nitpick, and why replying to krhodes1 with technicalities doesn’t do much good other than demonstrate you can read at a college level.

          • 0 avatar
            redav

            agenthex, and that makes this response, what exactly?

            “your reply is argumentatively poor”
            – No argument–I was merely clarifying some of the physics, because thermo is not typically well understood and often not intuitive. For future comments, I will remember that you have no interest in learning such details and that you don’t highly value precision and accuracy. If you aren’t interested in it, you are free to not read it or reply (twice). Hopefully, there *are* people who are interested in an engineering explanation rather than a layman’s approximation. (Also, please note that only one paragraph was directed at krhodes1’s comment–I didn’t really feel like posting multiple times when it all dealt with the same stuff.)

            “reciting from the textbook is bad technique”
            – Oh, don’t misunderstand. That’s no recitation; it’s considerably dumbed-down and condensed. I thought I explained the terms/concepts in an understandable way, but apparently not. Perhaps this isn’t about me reading at a college level, but rather that you seem to not want to?

          • 0 avatar

            > I was merely clarifying some of the physics, because thermo is not typically well understood and often not intuitive. For future comments, I will remember that you have no interest in learning such details and that you don’t highly value precision and accuracy

            Reciting an arbitrary classification in lieu of addressing the point is classic dumb student behavior. Not grasping the point altogether is classic dumb person behavior.

            As example of the former whereas pressure in this case is obviously dependent on temp, ie what most people consider “heat”, you use the word in a technical sense without proper explanation for the audience. This is both confusing/unhelpful and self-indulgent.

            As example of the latter this point was sufficiently clear in the contrast provided in what you replied to, yet here I am explaining it again.

            > Perhaps this isn’t about me reading at a college level, but rather that you seem to not want to?

            The people who read at a college level will continued to do so, and whose who can’t won’t learn in a couple paragraphs anyway. For example:

            http://www.thetruthaboutcars.com/2014/03/porsche-919-hybrid-lemans-racer-goes-after-the-two-thirds-of-gasolines-energy-thats-wasted-as-heat/#comment-2900681

            This explanation is adequate to the point wmba can go do the college reading for how second law thermo applies to engines, whereas poorly executed hand-holding by extolling on textbook exergy would’ve only made me look like you.

            What’s actually difficult to understand though is that I obviously reciprocate demeanor and hoes be getting pimp-handed left and right, yet bitches still cop an attitude like they feeling lucky.

    • 0 avatar
      redav

      Sigivald is correct.

      As a rough rule of thumb, a third of the gasoline’s energy becomes useful work. A third is wasted as heat, and a third is wasted as enthalpy (exhaust). “Heat” is the transfer of thermal energy (conduction, convection, radiation); “heat” is not the internal energy associated with something being hot. The state of ‘being hot’ is a part of enthalpy (internal energy + pressure energy), but it is not technically heat.

      krhodes1’s link is not rigorously correct. The point that the velocity of the gas is not the primary driver of the turbine is correct (because its kinetic energy doesn’t really change); however, the “heat energy” does not drive the turbine (since “heat” does not do mechanical work), nor does the gas being hot drive the turbine. This is demonstrated by the fact that a hot, low pressure gas will not drive a turbine, but a cold, high pressure gas will. It is enthalpy, not temperature, that matters.

      Going back to the article, there are two different strategies mentioned: extracting energy from heat loss (BMW’s TurboSteamer Rankine cycle) and extracting energy from enthalpy loss (turbine in the exhaust–a turbo).

      1. Rankine Cycle: This process works by taking a liquid, such as a coolant, and running it through a pump to increase its pressure, then running it through a heat exchanger (absorb heat from the engine and/or exhaust) to vaporize it. The hot gas drives a turbine to either generate electricity or add to torque to the drive shaft. Hottish (warm), low pressure gas comes out of the turbine and goes into another heat exchanger (reject heat to the environment through a radiator) where the gas condenses back to a liquid, and the process starts again. The article mentions the BMW’s system uses a two-stage cycle, which would indicate that there are multiple turbines, and likely the working fluid is reheated between them. (One such design could have the liquid go through the engine, then a turbine, then to the exhaust, and then a second turbine, then into the radiator.)
      2. Turbo: I think most car guys already understand this part. The high enthalpy exhaust coming out of the cylinder drives a turbine that can either do work (drive a shaft, increase intake pressure) or generate electricity. Intuitively, I expect the turbo to be placed before any exhaust heat exchanger because pulling heat out of the exhaust will lower its pressure, which reduces the effectiveness of the turbo.

      I have a couple designs very similar to what’s mentioned in the article, but I have yet to persuade our R&D company (which has an engine development group) to spend any money on them. I also have a slick design that uses the Peltier Effect (completely unrelated to cars), but no one wants to spend money on that one, either.

      • 0 avatar

        > This is demonstrated by the fact that a hot, low pressure gas will not drive a turbine, but a cold, high pressure gas will. It is enthalpy, not temperature, that matters.

        This seems rather a matter of classification since those two conditions won’t simultaneously hold.

        The important point is that the engine isn’t wasting its precious mechanical energy (eg pistons pushing on the compressor) to work a turbo.

        • 0 avatar
          CRConrad

          @agenthex: Which two conditions won’t simultaneously hold — a gas being hot and low pressure at the same time, or cold and high pressure, or what? Sure, not in an engine, where the pressure comes from combustion and therefore heat and pressure go hand in hand.

          But in principle, considering what will make a turbo turn, you can of course find both of those pairs of simultaneous conditions: Put a turbo in the hot low-pressure environment of your fireplace, and it won’t turn; attach it to a hose of cooled high-pressure air from an industrial compressor, and it’ll spin like crazy. Ergo: It’s pressure, not heat, that drives turbos. (Bad science warning: I’ve actually done neither experiment. But are you going to try to claim that wouldn’t be the outcome?)

          And if the throat of the turbo is constricted enough, or you put enough of a workload braking its spin, then I suppose the increased back-pressure in the exhaust system between piston surface and turbo vanes *will* actually sap those precious bodily fl– eh, mechanical energy — directly. How could it not?

          • 0 avatar

            > Which two conditions won’t simultaneously hold — a gas being hot and low pressure at the same time, or cold and high pressure, or what?

            Consider what happens when you heat a gas in a constrained shape (eg exhaust system). It helps here to understand what “temperature” *means*. What happens to the gas molecules and how does that relate to pressure?

          • 0 avatar
            CRConrad

            @agenthex: “It helps here to understand what “temperature” *means*. What happens to the gas molecules and how does that relate to pressure?”

            Yeah, well, I tried to do you the courtesy of assuming you had not only taken but passed high school physics. Since you seem incapable of reciprocating such basic manners, there’s not much use discussing with you. Next time you want to discuss something with someone, though, try this little tip: It helps to A) understand what you’re being asked, and B) Answer questions with answers, not condescending misguided questions of your own.

            (That is, I was asking: “Which ‘two conditions’ are you referring to — these here, or…?” The kind of answer that would have been conducive to an amiable discussion between adults would have been something like “Yes, that one”, or “Yes, both”, or “No, this completely different one…”, whatever the case might be. Now go take some remedial reading classes, in lieu of suggesting fifth-grade physics to people who actually followed that subject, oh, say, at least up to the stratospheric heights of tenth grade.)

          • 0 avatar

            >: It helps to A) understand what you’re being asked, and B) Answer questions with answers, not condescending misguided questions of your own.

            The main issue for someone who understands how things work explaining it to someone who generally doesn’t isn’t the “understands how thing work” part but the “generally doesn’t”.

            The confusing part of the scenario here is that the same physical reality can be represented with either energy or mechanically. Energy can be a very useful representation as highlighted above but also potentially unintuitive given its systemic nature. Therefore, the better explanation here is through the causal mechanics of how gases work.

            IOW, I could simply point you to the ideal gas law simplification, but then you likely don’t understand what temperature means in context of energy which makes it pointless (as evident in the comment this replies to). Therefore the attempt was made to foster some intuition of what happens mechanically when gas molecules are “heated” (ie higher temp) in a chamber. The answer had your mind been more capable is that they go faster, and thus hit the chamber walls faster, which is the definition of pressure. Therefore it’s simply nonsense to assume lower pressure and higher temp for the same gas in the same scenario.

            Alas even the 5th grade explanation failed which doesn’t bode well for those aspiring to a 10th grade one.

          • 0 avatar
            CRConrad

            Sigh… I notice that, in your third reply in this sub-thread, agenthex, you failed for the third time in a row to answer the question I’ve asked at least two (perhaps three?) times now: When you said “…since those two conditions won’t simultaneously hold”, which conditions were you talking about?

            “Therefore the attempt was made to foster some intuition…” Yes, indeed — I made the attempt to “foster some intuition” in you as to what you had been saying, by introducing a couple of alternative scenarios, but you seem to be far too busy trying to be snide — which really is getting rather tiring, by the way — to be able either to spare a few moments to go back and see what you’ve been saying, or just to clearly answer simple questions like “is this what you meant?”. I don’t know, does that sort of behaviour count as a winning debate tactic where you’re from, or something?

            “Therefore it’s simply nonsense to assume lower pressure and higher temp for the same gas in the same scenario” Yes, of course, _in the same scenario_ — but “the scenario” hadn’t been defined,and you’ve been refusing to respond to requests for clarification. “Therefore the attempt was made to foster some intuition” [TM Pompous Arseholes International, Inc] as to what element, exactly, of “the scenario” it is that drives a turbo by introducing a couple of different scenarios where “those two conditions” will indeed very well “simultaneously hold”. Funny, did you just not see that, or didn’t you understand it? All you had to do was ask — I’d be happy to clarify!

            “Alas even the 5th grade explanation failed which doesn’t bode well for those aspiring to a 10th grade one.” Well, no, it “failed” only in the sense of _your refusal to grasp_ that I very well understand all that already. As you so correctly point out, heating up a gas in a closed chamber leads to higher pressure. Further, which is where we seem to be losing you: This pressure is a mechanical force, which can be used to do mechanical work. It is _the pressure, not the “heat”(*) in and of itself_, that does the mechanical work.

            That was what @Sigvald said, and you contradicted him, siding with krhodes1 who claimed “heat energy” is the be-all and end-all. In words of no more than two syllables, so you’ll understand: Sigvald right, you wrong. You think you right, you show turbo in hot oven spin faster than turbo sprayed with cold air from big pump. Unil you can show that, you wrong and Siggy right, mmmkay?


            (*): As measured by actual temperature, so you won’t go into that whole “the same gas at a much lower temp in a much larger volume has the same amount of ‘potential heat’ in it…” blather. The obvious definition of heat was clearly the one Sigvald was using, and the appropriate one for a layman forum like this. Otherwise we get into “all energy is equal, only in different forms that can be converted into each other” territory — and then you and krhodes1 are *still* wrong with your “Turbos use heat energy, the mechanical flow is largely irrelevant”, because that’s obviously not “heat energy” but *chemical* energy that’s just happened to be converted into heat for a moment.

          • 0 avatar

            > When you said “…since those two conditions won’t simultaneously hold”, which conditions were you talking about?

            “a gas being 1. hot and low pressure at the same time, or 2. cold and high pressure”. You already named the conditions yourself. Repeating what you just said myself won’t really help matters.

            > This pressure is a mechanical force, which can be used to do mechanical work. It is _the pressure, not the “heat”(*) in and of itself_, that does the mechanical work.

            The two are necessarily constrained and therefore fungible here, esp since from a causal perspective it’s the heat in the gas that creates the pressure. This was sufficiently explained to redav so maybe he can help you out here because I can’t really make this simpler:

            http://www.thetruthaboutcars.com/2014/03/porsche-919-hybrid-lemans-racer-goes-after-the-two-thirds-of-gasolines-energy-thats-wasted-as-heat/#comment-2911489

            > Yes, of course, _in the same scenario_ — but “the scenario” hadn’t been defined,and you’ve been refusing to respond to requests for clarification.

            The scenario is the exhaust system before the turbo. I don’t know why you believe it might be a fireplace or whatever.

            > Further, which is where we seem to be losing you: This pressure is a mechanical force,

            I pointed out this arbitrary classification within an inherently energy-based a few times already. Again, redav seemed to eventually get it, maybe you will too some day.

            > then you and krhodes1 are *still* wrong with your “Turbos use heat energy, the mechanical flow is largely irrelevant”, because that’s obviously not “heat energy” but *chemical* energy that’s just happened to be converted into heat for a moment.

            The krhodes1 link attempts to disperse the misconception that the turbo is somehow driven by the mechanical pressure of the pistons, and it’s perfectly correct in this regard even if doesn’t use the terminology you prefer. Also, energy systems are generally agnostic to particulars of the form like chemical or “heat”, which is rather the point of them.

            > That was what @Sigvald said, and you contradicted him

            This is where we seem to be losing you. I didn’t contradict him, you only think that because you have no idea what’s going on here. Again, read the reply to redav and benefit from others’ mistakes.

          • 0 avatar
            CRConrad

            >> When you said “…since those two conditions won’t simultaneously hold”, which conditions were you talking about?

            >“a gas being 1. hot and low pressure at the same time, or 2. cold and high pressure”. You already named the conditions yourself. Repeating what you just said myself won’t really help matters.

            Oookay… So, we’ve established that you can count to two, but apparently not four: hot, low pressure, cold, high pressure. Which ones?

            >> This pressure is a mechanical force, which can be used to do mechanical work. It is _the pressure, not the “heat”(*) in and of itself_, that does the mechanical work.

            >The two are necessarily constrained and therefore fungible here, esp since from a causal perspective it’s the heat in the gas that creates the pressure. This was sufficiently explained to redav so maybe he can help you out here because I can’t really make this simpler:

            Blah, “fungible” blah… That’s another way of saying “All energy is one”, right? Which I’d already mentioned, I thought: Sure, all energy is always “fungible”; chemical energy equals heat energy equals mechanical energy equals gravitational potential (driving your car up a hill).

            But then why is _heat_, specifically, so apparently sacred in your religion that you have to claim “it’s the heat energy that does the work”, as if that form were somehow more fundamentally “energy”? (A fundamentalist, are you?) Why can’t you see that as one form that energy fleetingly occupies, equal in “rank” (or whatever it is that makes you prefer heat) to all other forms?

            >> Yes, of course, _in the same scenario_ — but “the scenario” hadn’t been defined,and you’ve been refusing to respond to requests for clarification.

            >”The scenario is the exhaust system before the turbo.”

            So, is that the scenario where a gas can’t be simultaneously hot and low-pressure, or the one where it can’t be simultaneously cold and high-pressure? I’m so confused, you see, because you said “these TWO conditions can’t exist simultaneously”, and I asked which _of the PAIRS_ (2*2=4) of conditions you meant, and you still haven’t said which.

            >”I don’t know why you believe it might be a fireplace or whatever.”

            And I don’t know which of the words “alternative” and “scenario” it is you don’t understand in the expression “alternative scenario”. Which one is it you need help with?

            Hey, I know languages and shit too, not just cars! Here’s a big cool word for you: “Gedankenexperiment”. That’s a German word, and old men with funny names like Einstein and Schrödinger and Heisenberg used to do it. It means “thought experiment”, like in reasoning about something without actually doing the concrete experiment.

            I have a Gedankenexperiment for you: Imagine two turbocompressors in different scenarios. One is in a hot oven, at high temperature and low pressure. The other one is having blown cold air at high pressure, from a compressor or something sprayed onto its turbine vanes. The experiment is this: Which one do you think would spin faster?

            You don’t HAVE to do this as a Gedankenexperiment; I’d love it if you did it as an actual physical experiment.

            But until you’ve answered — as you have failed to do on AT LEAST three occasions now, more probably five or six or so — at least what you THINK would happen, you really don’t have to reply to me any more at all.

            >> Further, which is where we seem to be losing you: This pressure is a mechanical force,

            >I pointed out this arbitrary classification within an inherently energy-based a few times already. Again, redav seemed to eventually get it, maybe you will too some day.

            A) within an inherently energy-based what?

            B) No, I get it. It’s you who doesn’t get it: Your calling the energy that drives the turbo “heat” is _just as_ arbitrary! If energy is “fungible”, then why should one have to see it as “really” the heat that does the job? (Especially given the Gedankenexperiment you seem to be afraid of doing, in light of which it seems to me that the form the energy takes in the moment it’s driving the turbo is more pressure-like than heat-like. Did you get a different result?)

            >> then you and krhodes1 are *still* wrong with your “Turbos use heat energy, the mechanical flow is largely irrelevant”, because that’s obviously not “heat energy” but *chemical* energy that’s just happened to be converted into heat for a moment.

            >The krhodes1 link attempts to disperse the misconception that the turbo is somehow driven by the mechanical pressure of the pistons, and it’s perfectly correct in this regard even if doesn’t use the terminology you prefer. Also, energy systems are generally agnostic to particulars of the form like chemical or “heat”, which is rather the point of them.

            So, if I prefer another terminology than that link, then I’m wrong; but if you prefer another terminology, then you’re in your good rights to so prefer? Even though enetrgy is fungible, and all terminology therefore equivalent? Good to know.

            >> That was what @Sigvald said, and you contradicted him

            >This is where we seem to be losing you. I didn’t contradict him, you only think that because you have no idea what’s going on here. Again, read the reply to redav and benefit from others’ mistakes.

            I really love how you’re so convinced you know a zillion times better than everybody else. From where I stand, it’s you who has no idea what’s going on here: Energy is fungible; in an engine it is transformed from chemical to heat to mechanical; according to simple laymen, it is in the mechanical form that it does its work, and they call this form of energy “pressure”.

            What’s going on, though, is that apparently the High Priests of Heat won’t allow any terminology that calls the energy that does mechanical work “pressure”, for it shall be called Heat, and Heat is what it shall be called.

            So, do you think it’s “heat” that forces the piston down, too, or is one allowed to call *that* “pressure”?

            Oh, and in those two alternative scenarios — the ones you “don’t know why [I] believe it might be a fireplace or whatever”, as if the idea of introducing additional scenarios is somehow Anathema, too — which one DO you think will spin faster, the one in the oven or the one under the compressor?

            Please, PLEASE don’t bother to reply unles you answer that, too.

          • 0 avatar

            > Oookay… So, we’ve established that you can count to two, but apparently not four: hot, low pressure, cold, high pressure. Which ones?

            If you can’t even grasp *your own writing* (with annotations no less), what makes you believe that interpreting others’ is within reach? Serious question.

            This whole energy business is clearly not working out for you, and taking to shiitposting about what you can’t understand isn’t going to help.

            It’s likely these poor learning habits persisted from earlier days, which rather succinctly explains the abysmal level of science comprehension (as if it were a rhetorical game). I’m won’t claim to be a better educator than all those who’ve failed before.

          • 0 avatar
            CRConrad

            Serious answer:

            agenthex, March 5th, 2014 at 4:31 pm (http://www.thetruthaboutcars.com/2014/03/porsche-919-hybrid-lemans-racer-goes-after-the-two-thirds-of-gasolines-energy-thats-wasted-as-heat/#comment-2906097): “This seems rather a matter of classification since those two conditions won’t simultaneously hold.”

            CRConrad, March 14th, 2014 at 7:58 am (http://www.thetruthaboutcars.com/2014/03/porsche-919-hybrid-lemans-racer-goes-after-the-two-thirds-of-gasolines-energy-thats-wasted-as-heat/#comment-2951074): “@agenthex: Which two conditions won’t simultaneously hold — a gas being hot and low pressure at the same time[=2], or cold and high pressure[=2], or what?” [=2+2=4]

            agenthex, March 14th, 2014 at 2:33 pm (http://www.thetruthaboutcars.com/2014/03/porsche-919-hybrid-lemans-racer-goes-after-the-two-thirds-of-gasolines-energy-thats-wasted-as-heat/#comment-2953386): [Condescension, no reply]

            CRConrad, March 17th, 2014 at 8:31 am (http://www.thetruthaboutcars.com/2014/03/porsche-919-hybrid-lemans-racer-goes-after-the-two-thirds-of-gasolines-energy-thats-wasted-as-heat/#comment-2959689): “Answer questions with answers, not condescending misguided questions of your own.

            (That is, I was asking: “Which ‘two conditions’ are you referring to — these here, or…?” The kind of answer that would have been conducive to an amiable discussion between adults would have been something like “Yes, that one”, or “Yes, both”, or “No, this completely different one…”, whatever the case might be.”

            agenthex, March 17th, 2014 at 2:01 pm (http://www.thetruthaboutcars.com/2014/03/porsche-919-hybrid-lemans-racer-goes-after-the-two-thirds-of-gasolines-energy-thats-wasted-as-heat/#comment-2961393): [More condescension, still no reply]

            CRConrad, March 17th, 2014 at 8:16 pm (http://www.thetruthaboutcars.com/2014/03/porsche-919-hybrid-lemans-racer-goes-after-the-two-thirds-of-gasolines-energy-thats-wasted-as-heat/#comment-2963737): “I’ve asked at least two (perhaps three?) times now: When you said “…since those two conditions won’t simultaneously hold”, which conditions were you talking about?”

            agenthex, March 17th, 2014 at 8:59 pm (http://www.thetruthaboutcars.com/2014/03/porsche-919-hybrid-lemans-racer-goes-after-the-two-thirds-of-gasolines-energy-thats-wasted-as-heat/#comment-2963897): “> When you said “…since those two conditions won’t simultaneously hold”, which conditions were you talking about?

            “a gas being 1. hot and low pressure at the same time, or 2. cold and high pressure”. You already named the conditions yourself. Repeating what you just said myself won’t really help matters.”

            Your “1.” is what I have the whole time been asking about as one set of two conditions; your “2.” is another such pair. Yes, I misread you to begin with. Sorry, my mistake, I get it now.

            But if you meant each such _pair_ as *one* “condition”… I dunno, maybe you could have said so? Perhaps one of the first few times I asked? Hey, just an idea. What with your immensely superior intellect — as you’ve so amply demonstrated, at least to your own satisfaction — it should have been laughably easy for you to spot my blunder and point it out somewhere before the fourth time I asked.

            Or maybe you didn’t understand why I asked this because *you* couldn’t grasp my writing to see that I was talking about the two pairs separately, as four conditions, total? Or even because YOU “can’t even grasp *your own writing* (with annotations no less)”, to see that you had (arguably, in my AFAICS quite reasonable first interpretation) been talking about four conditions, not two?

            Sorry, but claiming *I* “can’t even grasp *your own writing* (with annotations no less)”, when I’ve been annotating both my own and your writings for you, with *you* apparently not being able to grasp what I’m asking — at least as evinced by your consistent non-answers — that’s just bullshit.

            But, hey, you’ve accompanied that with a whole lot of other faeces-slinging too, designed to show how utterly superior you are and how little others know… All the while in other posts you’ve accused others of doing exactly that.

            You might think you’re coming off as a winner here, but you’re not.

          • 0 avatar
            Jack Baruth

            Gentlemen,

            Take a break on this one. You’re not going to convince each other right now and I value both of your contributions. Okay?

          • 0 avatar

            Jack, please allow a last brief note which probably clarifies the root of this mess; I promise to be nice.

            > But if you meant each such _pair_ as *one* “condition”… I dunno, maybe you could have said so?

            It was only ever the two conditions which redav brought up. There was never 4 to start with.

        • 0 avatar
          CRConrad

          @Jack Baruth: “Take a break on this one. You’re not going to convince each other right now and I value both of your contributions. Okay?”

          Sorry, no. You’re implying that this was just a disagreement about facts, and that’s bogus. This had become a matter of manners long before your feeble intervention; “Agent Hex” / “You Mad Scientis” was (is) in the wrong there even more than on the facts.

          Which apparently became so obvious that someone was forced to recognise it officially by banning the above user ID? It’s rather transparent, though, that he’s back and his behaviour hasn’t improved at all in the mean time.

          Unless you make sure it’s permanent and comprehensive, your ban is as meaningless as your admonition here. Your actions hereafter will tell us how much you *really* value that civilised behaviour you’ve been talking about.

          • 0 avatar

            > Unless you make sure it’s permanent and comprehensive, your ban is as meaningless as your admonition here. Your actions hereafter will tell us how much you *really* value that civilised behaviour you’ve been talking about.

            Whether it’s physics, computers, or ttac, there seems to be a common pattern here.

            B&B indeed.

          • 0 avatar
            CRConrad

            There, Jack, what more proof do you need?

          • 0 avatar

            > There, Jack, what more proof do you need?

            Sigh. Let’s just say Baruth understands how ttac works, too.

      • 0 avatar
        Dr. Kenneth Noisewater

        How efficient are Peltier/Seebeck materials these days? They don’t seem practical, but the last time I dealt with them was when I was overclocking dual Celerons :p

        • 0 avatar
          redav

          I think the number is around 10%, but may be more if you’re willing to pay for it.

          • 0 avatar

            > I think the number is around 10%

            Surely someone so scholarly can produce a proper scholar answer as done below, which you already saw but perhaps didn’t see fit to parrot:

            http://www.thetruthaboutcars.com/2014/03/porsche-919-hybrid-lemans-racer-goes-after-the-two-thirds-of-gasolines-energy-thats-wasted-as-heat/#comment-2901601

  • avatar
    James2

    Has there ever been such an ugly race car? Slab-sided, a front end as bluff as a bus, and that dorsal wing from F1 cars a few years back… it adds up to fugly.

  • avatar
    NMGOM

    I thought for sure that Porsche was going to announce some breakthrough in thermo-electric (TE) technology in which one could wrap the entire exhaust system in what would appear to be the inverse of heater tape.

    Another idea:
    Yes, an inverse turbo can still collect energy from heat, but if the entire exhaust system went through something like a radiator (but for gases, as in an air-air inter-cooler such as those on a Pro-Comp Supercharger), then embedding TE wires within that matrix might silently, without further mechanical devices, perhaps harvest a higher % of the heat for electricity than the inverse turbo?

    Need to know: TE conversion efficiency: %∆H / %∆ E .

    What do you think? Anyone?

    ————————

    • 0 avatar

      Let’s say TE w/ zT ~1 and exhaust scavenge 50% as heat and ~500degK, I assume you can do the math…

      http://www.thetruthaboutcars.com/2014/02/qotd-toyota-not-tesla-as-a-force-of-disruption/#comment-2892937

    • 0 avatar
      redav

      I suspect there’s a power problem. Any heat transfer you do with the exhaust has to happen quickly (because otherwise it slows down the engine), and it’s possible that electronics can’t keep up.

  • avatar
    MBella

    I’m curious to see what comes out of these concepts of reclaiming exhaust heat. I also see a large scale use of ceramics in engines allowing way higher engine operating temperatures with almost no need for engine cooling, another huge energy waster.

    • 0 avatar
      redav

      “For SkyActiv 3, Mazda is pursuing adiabatic combustion, using insulation and possibly ceramic materials to minimize cooling-related efficiency losses”
      http://www.sae.org/magazines/pdf/14MEIP03.pdf

      I don’t know how they would pull this off–it sounds like a pie-in-the-sky target. I know simply insulating the engine doesn’t lead to much higher work output; instead, most of the heat loss just turns into enthalpy that gets dumped out the exhaust. But maybe an extreme form of an Atkinson cycle engine (where the expansion stroke is much longer than the compression stroke) could extract enough energy (and thus cool the exhaust) + big ass turbo would work.

  • avatar
    tjh8402

    thank you for posting that chassis cut away. rare that you get that good of a look at an LMP chassis. truly an F1 car with fenders.

  • avatar
    DeadWeight

    I feel as if I should have known that so much of the energy contained in gasoline is cast off as heat rather than driveshaft energy as a result of combustion in an ICE, but I did not.

    In fact, I would’ve been “off” by 50% if I had been forced to guesstimate how much of the energy in gasoline was essentially lost in the form of heat.

    It’s really an incredible thing that this is so…well, at least to me, as I’m neither a physicist nor engineer.

  • avatar
    ExPatBrit

    “KERS-like system”

    Kinetic Energy Recovery System, the second use of the word “system ‘ is redundant.

    • 0 avatar
      CRConrad

      @ExPatBrit: So you’re saying “The Impreza WRX is a CSC-like car.” would be redundant, and “The Impreza WRX is a CSC-like.” correct, if “CSC” meant “Chinese Super Car”? But if it meant, say, “Chinese Super Corporation”, then “The Impreza WRX is a CSC-like car.” would become correct and “The Impreza WRX is a CSC-like.” ungrammatical?

      I don’t think it works quite like that.


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