Are hydrogen engines more efficient than gasoline engines?

[SmallIsPower]

I'm quite aware of the Second Law of Theromdynamics and have considered "The Hydrogen Economy" a joke, because to get the hydrogen one would either have to break up water (obviously inefficient) to reconsitute it, or break up fossil fuels to create the hydrogen, also degrading the energy.

 

Recently I've been reading that hydrogen engines are potentially so much more efficient than gasoline engines, that the loss in covering gasoline to hydrogen is more than made up by the efficiency of hydrogen engines.

 

This still looks like hype from people who want to push hydrogen, but I don't have all the facts, is there something I'm missing?

[ecoli]

On the plus side, you're switching from non-point source pollution (cars) to point source pollution (factories where Hydrogen is generated). Pollution from point sources are much easier to measure and control.

[insane_alien]

Well when we switch over to fusion power it won't be much of a problem we'll have oodles of power with very little cost and we'll be breaking up water anyway to get deuterium to fuel the reactors unless we find a suitable method for p-p fusion. so the unusable hydrogen can go to fueling our cars etc.

[SmallIsPower]

Of course, same with huge solar and wind farms, but are hydrogen engines more efficient than gasoline?

[ecoli]

Of course, same with huge solar and wind farms, but are hydrogen engines more efficient than gasoline?

 

it's about 2 times more efficent. http://en.wikipedia.org/wiki/Hydrogen_car

 

20-30% for gas engines, 50-60% for hydrogen engines.

[SmallIsPower]

Oops! I've spent months saying the second law made it obvious that hydrogen cars would be less efficient.

 

My mom warned me that "A little knowledge is a dangerous thing." I thought I'd had enough knowlegde. Thanks ecoli.

[Pleiades]

I thought I read somewhere that water can be split up at efficiencies approaching 100%. I don’t know about recombining it though.

[Rebiu]

I'm quite aware of the Second Law of Theromdynamics[/b'] and have considered "The Hydrogen Economy" a joke, because to get the hydrogen one would either have to break up water (obviously inefficient) to reconsitute it, or break up fossil fuels to create the hydrogen, also degrading the energy.

The issue with energy is not its availability, but having it where you need it, when you need it, and in a form you can use. Hydrogen with never work if one uses fossil fuels to make the hydrogen.

 

Recently I've been reading that hydrogen engines are potentially so much more efficient than gasoline engines' date=' that the loss in covering gasoline to hydrogen is more than made up by the efficiency of hydrogen engines.[/quote']That is interesting. Consider that byproduct of electolysis is pure oxygen. Most of the energy of combustion is used up in heating the five parts inert Nitrogen in air per one part hydrogen. No naturaly aspired engine can compete with pure oxygen combustion.

 

This still looks like hype from people who want to push hydrogen' date=' but I don't have all the facts, is there something I'm missing?[/quote']Hydrogen is not a good solution at this time because of the inefficiency of hydrogen production and storage. The real solution is biodiesel made from plant algae. This technology is proven and capable of entirely replacing all forms of energy production on the planet. It will work with existing diesel technology as well.

[swansont]

it's about 2 times more efficent. http://en.wikipedia.org/wiki/Hydrogen_car

 

20-30% for gas engines' date=' 50-60% for hydrogen engines.[/quote']

 

It's not clear that they have included inefficiencies in producing the hydrogen, nor if this is a comparison of hydrogen in a fuel cell or internal combustion engine. Since it's in the "fuel cell" section, I would assume that they are comparing to a fuel cell. So you really have to compare to a system that uses gasoline in a fuel cell, for an "apples-to-apples" comparison, and you have to look at all phases of the system, or you ignore the possibility that you are just shifting the inefficiencies out of the picture.

 

This article states that "At 13 percent, the well-to-wheel efficiency of the fuel-cell option with hydrogen produced by electrolysis is lowest of the options we studied."

[SmallIsPower]

That seems to make more sense. I just kept on hearing more and more hydrogen hype, and I was starting to wonder if it was true.

[chilehed]

A friend of mine worked on fuel-cell vehicles for a while. Their system used an on-board reformer that scavenged the hydrogen from gasoline for use in the fuel cell, and burned the carbon as the heat source to operate the reformer. The emissions were CO2 from the reformer and H2O from the fuel cell.

 

My understanding is that the largest inefficiency in combustion engines is due to uncontrolled electron sharing during the reaction. Fuel cells don't suffer this loss because once an electon is free it's sent through the circuit to be used. So even though none of the heat from the oxidation of the carbon got used to move the vehicle, the high efficiency of the hyrdogen side of the process was more than enough to make up for it.

 

It was promising, but the company went belly-up due to lack of investment capital.

 

If you're asking about a comparison between two internal combusion engines, one fueled by gasoline and the other by hydrogen, then hydrogen wins hands down (assuming you can optimise both for compression and fuel/spark calibration). The single biggest driver for efficiency in an IC engine is compression ratio, which is limited by the octane rating of the fuel. Hydrogen has an octane rating around 140, which means you can raise the compression ratio a lot higher than on a gas engine. And since H2 is gaseous, a lot of the mixture distribution problems you can encounter with liquid fuels just go away.

[padren]

I think the question sort of boils down to:

 

If you took a gallon of gasoline, and used it in a car to do Work in the Newtonian sense, then took a gallon of gasoline, used it to make as much hydrogen as you could with that gallon, then used the hydrogen in a hydrogen engine car to do Work...which would do more work?

 

I think that is the apples to apples comparison, but it ends up more complicated since most hydrogen production is often done with many different technologies and on different scales.

You can produce hydrogen with nuclear power, but cannot produce gasoline with nuclear power, so the latter is effectively "0%" effecient and the ability to compare "apples to apples" breaks down.

 

How you use gasoline to produce hydrogen for the direct comparison can vary too, and since you can use a centralized plant that does not need to fit in a car for that portion of production, I can only imagine it would be done more effeciently than an auto engine ever could.

[silkworm]

Does converting hydrogen and oxygen to water release more energy than burning fossil fuels? No.

 

Are hydrogen fuel cells more effecient? No, percent usage yes. Bang for volume, no.

 

At our current technology is it feasable to get the sort of range out of a fuel cell than you can out of a gas tank? No.

 

What's so great about hydrogen fuel cells? Their waste product is water, and its emissions will not produce greenhouse gases/pollution.

 

It's actually quite easy to make hydrogen. We don't have to use fossil fuels to do so either. You can do it with water and a solar panel. No big whoop. We won't spend anything (energy wise except for in distribution and manufacturing), just harvesting energy we don't use. A wind farm could also crank out a lot.

 

Probably the biggest obstacle is making a highly pressurized tank full of a volatile material that average guy won't end up getting himself and others killed with by drunk driving.

 

By the way, your butchering of the second law is pretty common, especially among IDers and other proclaimers. No one ever considers the energy released or even really what the hell "disorder" is, and for that matter what system we're talking about. Don't feel bad about it if you're new to the idea.

[Cap'n Refsmmat]

Probably the biggest obstacle is making a highly pressurized tank full of a volatile material that average guy won't end up getting himself and others killed with by drunk driving.

Hydrogen isn't actually that much of a problem. I've seen demonstrations with a comparison of a gas leak vs a hydrogen leak. Hydrogen has the advantage that it just burns in a nice little flame going straight up, while gasoline just goes FWOOSH and the whole place burns up.

 

Though if you got a tank to completely explode and spread out the hydrogen in a nice distribution, you could have a very nice fireball.

[silkworm]

Though if you got a tank to completely explode and spread out the hydrogen in a nice distribution, you could have a very nice fireball.

 

Exactly. Pressurized gas. Leaking tank. Spark. Problem. It's pressurized gas, and to get decent range it either has to be highly pressurized or too large to be practical.

[padren]

Exactly. Pressurized gas. Leaking tank. Spark. Problem. It's pressurized gas, and to get decent range it either has to be highly pressurized or too large to be practical.

 

If I recall, one nice factor is that most anything that is a source of combustion (spark, burning tire, anything really) would be on or close to the ground, and leaking hydrogen will go straight up in a real hurry.

 

Its the liquid and denser than air gas combustables that are really dangerous when there is a leak.

 

That said about cars...heating your house with a hydrogen tank in your basement would be very bad if it leaked.

[wgargan]

i get the feeling from what most are saying is that to produce hydrogen from electricity, electrolytes and water is not efficient. How about producing hydrogen with NaOH, Al and H2O. Lets forget about Fuel cell cars, batteries and electric motors etc... ( think about all that waste) lets think of an adaptable technology. One that i could buy in the form of a kit install it in my Gasoline powered car, dump in some Lye some old beer cans and fill up my tank with the hose and be on my with hydrogen. IMHO, internal combustion engines is the only way to really get the public familiar with H2 technology. For the most part, people think of hiroshima when the word hydrogen is mentioned. As mentioned above this is not even close to a hydrogen burn. Hydrogen burn is quick, hot and will go straight up in the air. petrolium burns, well lets just say, you do not want to be trapped in the car if your gas tank catches fire.

will

[swansont]

For the most part' date=' people think of hiroshima when the word hydrogen is mentioned. As mentioned above this is not even close to a hydrogen burn. Hydrogen burn is quick, hot and will go straight up in the air. petrolium burns, well lets just say, you do not want to be trapped in the car if your gas tank catches fire.

will[/quote']

 

 

They do? I would have guessed "Hindenberg"

[wgargan]

They do? I would have guessed "Hindenberg"

 

all i have heard form people is " i dont want to ride around with a hydrogen bomb. What if i got into a wreck" you have to admit that in the states many people are confused when it comes to words that are used in many different topics

[chilehed]

If you took a gallon of gasoline, and used it in a car to do Work in the Newtonian sense, then took a gallon of gasoline, used it to make as much hydrogen as you could with that gallon, then used the hydrogen in a hydrogen engine car to do Work...which would do more work?

That's a subtly different question.

 

The heating value of a stoichiometric mixture of vaporized gasoline is about 16% greater than an identical volume of a mixture of hydrogen. Even if you jack the compression ratio up to take advantage of the higher octane rating of hydrogen you won't be able to get an 16% improvement in thermal efficiency, so right there you'll get less distance down the road using hydrogen. Add to that the fact that you'll only be using a part of the total heat value of the fuel if you strip the hydrogen from gasoline, and you'll go less distance still. The only way to make up for the loss of heating value is to have a very, very efficient hydrogen reaction, which means you don't use a combustion engine.

 

The safety risks of compressed hydrogen are way overblown (no pun intended). Certainly you don't want the tanks to rupture, but they're pretty tough. As for leaks, the flammability limits for hydrogen are very narrow (so it's easy for the mixture to be either too lean or too rich to burn) and the stuff is so volatile that it dissipates very quickly.

[swansont]

all i have heard form people is " i dont want to ride around with a hydrogen bomb. What if i got into a wreck" you have to admit that in the states many people are confused when it comes to words that are used in many different topics

 

Hiroshima wasn't a hydrogen bomb, though.

 

Anyway, there are storage strategies that do not depend on high pressure, like metal hydrides.

[Norman Albers]

In junior high school we electrolyzed water and something into two test tubes and got oxygen and hydrogen, quite cool especially when the teacher lit a match and the H2 tube popped at about a double-high C (short organ pipe) . Is this safe??? It seemed so as it wasn't too strong but is this still done? The point is that this is easily suited to low voltage solar panel output. Is this still not economically down in price?

[insane_alien]

its only safe if its a test tube(the standard ones not the bigger variety). anything larger can cause the vessel to explode. and send glass flying. not a good thing.

[Norman Albers]

Good enough. This brings up a question of thermodynamic energy per mass. Is there something inefficient, like having to operate a heat cycle at low pressure differentials? Think of autos, where higher compression ratio gets you fundamentally higher thermo effeiciency.

[swansont]

The point is that this is easily suited to low voltage solar panel output. Is this still not economically down in price?

 

IIRC photovoltaic cells currently rely on castoffs from other semiconductor production, i.e. cheap materials are available, and there is concern that a significant ramp-up in production would actually increase cost.

 

But the real issue is storage and transport, not production so much.