Submitted for your perusal: Truckers choose hydrogen power. According to this article in the alledgedly reputable Wired,
Alrighty then. I’m no trucker, but I do know this: This HFI injects hydrogen into the fuel mixture. The hydrogen is obtained by electrolysis of water on board the truck. The electricity for that is drawn from the alternator. The alternator is powered by…the engine! How could they possibly get enough energy out of this system to save fuel? The electrolysizer(?) would add load to the engine, making it use more fuel anyway. What’s the deal?
Maybe what they’re saying is that it’s not the power from the combustion of the hydrogen that’s important, it’s that somehow the hydrogen being there causes the combustion of the diesel fuel to be more efficient. It sounds marginally plausible to me, so I’d definitely want to see good data.
If the amount of gas saved by burning a hydrogen-diesel mixture is greater than the gas used to electrolyze the water, then hydrogen is just a catalyst which facilitates the burning of diesel. It’s concievable (but suspicious) that it would work as advertised.
Overall, you’re not creating energy out of nothing. You’re getting more energy out of the diesel you burn and less unburnt diesel.
And that seems to be the idea: hydrogen + diesel produces significantly more energy than dielsel alone. When you think about it electric injectors work pretty much the same trick: This EFI injects diesel into the cylinders. The electricity for that is drawn from the alternator. The alternator is powered by…the engine! Yet EFI is not a scam, nor is it in any way free energy, it’s just that investing a small amount of energy into the injectors returns a shitload more energy than it costs. That’s synergism for you, the energy return from the the injectors and the cylinders working together is far greater than the energy return from either alone.
Of course EFi has provable benefits and is not a scam, The same may not be true of this device. Nonetheless the fact that engines can utilise synergistic devices powered by the alternator means that it doesn’t need to be be a scam.
I find this a bit glib. Chemists have a rather specific definition of a catalyst. By contrast, the concept of a “synergist” is rather a vague one. One source has: “an agent that increases the effectiveness of another agent when combined with it; especially : a drug that acts in synergism with another.” IOW, if small amounts of hydrogen improve efficiency, it should be possible to say why in some detail. Saying it’s synergistic is like saying “it helps”.
And by extension, so do wheels - they represent some drag, but you get considerably better fuel efficiency with wheels than you do with the hubs alone.
Um…no. The “consensus” has not yet explained how you get more energy out of burning hydrogen electrolyzed from water than it takes to generate said electricity and subsequently use it to electrolyze the water. If it’s doing that, then it’s most likely a perpetual motion machine. And then it damn well does violate the laws of thermodynamics.
The efficiency of electrolysis nowadays is about 75%, with some laboratory systems reputedly up to 80%. OK, let’s say 80%. The efficiency of an automobile alternator can get as high as 70% (from Bosch). How do you generate electricity at 70% efficiency, then use that in an 80% efficient process, to produce enough additional power to pay for itself?
Oh, they’re running out the “increases combustion efficiency” gimmick. However, current IC engine combustion efficiency is already very high - for a modern diesel, more than 90% or so. In fact, according to my best textbook (“Internal Combustion Engine Fundamentals” by Heywood), typical SI engine combustion efficiency is between 95-98% at typical air/fuel ratios, and IIRC diesel is about 90-96%. That differential between 90% and 100% does not make up for the differential between generation and use of the electricity alone. If we could do that, we’d have the world renewable energy situation solved.
That’s not talking about combustion efficiency at all, it’s talking about overall cycle efficiency. And it’s not relevant to the core issue if the item simply doesn’t do what it says it does.
This stuff doesn’t even an engineering degree, just common sense. Anyone here who thinks it’s possible want to explain how you get more energy out of this system then you put into it?
OK, the challenge stands even moreso - how do you leverage that last 2% of inefficiency to generate electricity at 70% efficiency and electrolyze water at 80% efficiency, and somehow still produce more energy than goes into it? They’re not measureably changing the engine frictional losses, they’re not measureably changing the thermal losses to the coolant and exhaust (in fact, adding hydrogen is going to increase the latent heat losses in the exhaust)…so tell me, exactly how is it possible?
Isn’t the last sentence at odds with the first sentence?
I think you have to know how much hydrogen is required. For instance, suppose that we have an engine that has 98% combustion efficiency. For every 1000 BTUs of energy contained in the fuel, this engine can provide 980 BTUs in available energy. Increasing the combustion efficiency to 99% provides 10 more BTUs. Is it worth it? It depends on how much hydrogen is required to go from 98% to 99%. If it takes less than 5.6 BTUs of energy to electrolyze the amount of water needed to create that hydrogen, then it is worth it or at least break even (of course, the number is probably a bit higher than that as you are going to recover some of that energy by burning the hydrogen, but we’d need more details about the entire power cycle to determine what that is).
I’m not convinced that it works, but I don’t think it’s impossible.
I didn’t get a good look at the link yet (slow connection), but I am wondering if this is really just a water injector which adds moist air to fuel, and in gas engines, will lower combustion temps, slowing combustion, which may allow lower octane fuel and increase mpg (I’s not sure if there was a diesel version). From what I recall water injectors did work, but were a bit of a PITA as you had to fill it up often and protect to from freezing.
I can see a few good arguments already, but without numbers I can’t conclusively prove anything.
(1) In the status quo, the engine “breathes” standard air, and uses only the chemical energy in the fuel, so the efficiency of the engine is measured against the theoretical maximum efficiency of that fuel burned in air. So while you state the 96% number for an air-breathing diesel, this new engine breathes air and hydrogen, so (if you’ll pardon a Spinal Tap metaphor) it goes one louder – up to eleven. Its overall efficiency might be reduced by the electrolysis, but its total energy output per gallon of diesel consumed could still be higher. Just remember that it’s not just consuming diesel; it’s also consuming the chemical bonds in distilled water.
(2) One of the most revealing remarks in the article was that
If 50% less unburned fuel is leaving the system, then more fuel is being burned in the system. I agree with you that “they’re not measureably changing the thermal losses to the coolant and exhaust” but surely you can see that burning a higher percentage of the fuel is going to yield a not-insignificant benefit. That 50% could drive the combustion efficiency you cited (98%) up to 99%; not sure how that results in a 10% fuel savings, though.
I’m going to throw some energy numbers out based on kanicbird’s train of thought and see if I can make sense of them:
Energy content of diesel fuel: 44.4 kJ/g (converted from BTU/gal) (cite)
Energy content of gaseous hydrogen:120.7 kJ/g (cite)
If electrolysis and generation have the losses you stated (80% and 70% efficiencies) then you have to pay 215 kJ to get a gram of hydrogen. If the resulting boost in theoretical peak efficiency is only (making up a number here!) one-tenth of a percent, you’re still squeezing an extra 40 J out of each gram of diesel you use.
Diesel weighs 3.13 kg / gallon, so in the first scenario, you’re trickling out a gram of hydrogen for every 1.3 gallons or so – that’s not very much, and probably not enough to get you your tenth-of-a-percent. But somewhere on that curve there’s a synergy, where adding a gram of hydrogen to (let’s say) .15 gallons gives you a one percent boost in efficiency. The manufacturer “guarantees 10 percent fuel savings” so perhaps the sweet spot is closer to a gram of hydrogen in each .015 gallons. With better electrolysis and/or generation efficiency, the cost to pay the piper here is not really all that high.
In terms of emissions, very small changes of efficiency can mean the difference between meeting a limit or not. Witness the latest trends to move SO2 scrubber efficiency up from 94% to 98%. I’m working on a plant right now that cannot operate legally in 2008 unless they get that 4% increase.
I guess I figured most people read the article and should have been bothered by the “guarantees a 10% fuel savings” issue, which is where the thermo impossibility happens. How is that happening, when combustion efficiency is already maybe 98%? Once again, just common sense here.
Say you’re taking 1000 Btu/hr of energy into the system and combusting to get 980 Btu/hr of heat release. That leaves 20 Btu/hr which could be recovered, in theory, somehow. If this is increased to 990 Btu/hr by going to 99% efficiency, then that’s 10 extra Btu/hr. To generate 10 Btu/hr of hydrogen power, you’re going to need 10 (0.7*0.8) = 17.9 Btu/hr of power from the engine (possibly more, depending on assumptions). But since the assumption is that this is lost fuel that is somehow being recovered, they’re saying that all you need to do is use less than 5.6 Btu/hr of hydrogen to break even? (actually, you need more than that because of the fact that all the hydrogen ends up as water vapour, and thus has a large latent heat loss component). Why does that happen, exactly? Through what mechanism? Just the fact that hydrogen burns better? That doesn’t necessarily translate to anything with diesel fuel - diesel fuels are long-chain hydrocarbons (relative to say, gasoline) and much of what does not burn is a result of what sticks in the oil on the cylinder walls, the very low-volatile compounds, and so forth. They claim lower emissions, and maybe that’s true - but translating particulates to efficiency loss is always tricky. If particualtes burn to CO and not CO2, for example, you have a sizeable difference in energy.
And yet, at the end of it all, you get a 10% fuel savings?
And that’s what bothers me. They’re not backing up their claim that they are doing this, nor is there any way that a 10% savings comes from this.
Yes but can you count the hydrogen as you have to use that very energy to make it? It’s true that you could ajust things that you are making H2 when your engine is at a low demand state and use it during a high demand state, which may increase efficencies.
Also what is done with the O2 which would be also produced? It seems like that would also be benificial to put into the air intake.
I wasn’t trying to address the 10% fuel savings, and I’m sure that I’m just as supsicious of advertising claims as you are.
I’m just not convinced that this is neccesarily in violation of the laws of thermodynamics, especially if a hydrogen/fuel oil mix does indeed burn more completely than straight fuel oil, and if so, under what conditions.
Does the 98% combustion efficiency happen at all engine operating conditions, or only at a specific operating point? If less efficient conditions exist, say during acceleration from idle to 2000 prm under load, then increasing the efficiency at these points has a higher possible benefit. That just guessing though. I don’t know if the diesel engine operates at anything less than 98% combustion efficiency at any point.
