Using a gas engine to turn an alternator to power an electrolytic cell to obtain burnable hydrogen is horribly inefficient. But then again, so is using a gas engine to turn a generator to charge a battery that in turn powers an electric motor. However, this didn’t stop the development of hybrids, which really do save fuel. If you could design a “Brown’s Gas” system so that it only generated the gas when the vehicle was decelerating or idling, then the hydrogen would be created using energy that would otherwise be wasted.
So the guy modifying his cars could be telling the truth, if he set it up to operate like a hybrid.
I’m not sure how you’re going to “set it up to operate like a hybrid.”
Parallel hybrid electric vehicles improve efficiency by:
a) having smaller engines (because peak torque requirements can be shared between the gasoline and electric systems, reducing the required size of the engine). Smaller engines are more efficient at a given power output than larger engines are.
b) recovering braking energy
c) allowing engine-off operation
d) (sometimes) managing engine speed and torque operation to maximize efficiency (re the Prius)
I don’t see how using electricity to produce hydrogen will allow you to do any of these things.
Only one of the features you mention is necessarily exclusive to hybrids. You can make a non-hybrid with a smaller engine, or that turns off when it is idling, or uses a continuously variable transmission to keep the engine speed at peak performance.
Recovering what you call “braking energy” is what I am talking about. But it isn’t just braking. I own a hybrid, and anytime you decelerate, whether by braking or by simply taking your foot off the gas, the generator kicks in and starts charging the batteries.
All I am saying is that if you can use deceleration (or braking energy) to charge batteries, like a gas-electric hybrid does, you can also use it to make hydrogen.
Well, doesn’t the alternator waste a lot of electricity?
I remember on my first couple of cars, if I accidentally let the battery get low (leaving on the after-market defroster, for example :rolleyes: ) the needle that showed the recharging was a lot further to the right than normal. When it’s not busy recharging a severely low battery, isn’t it wasting electriticy (or at least energy it could be using to generate electricity)?
You could do that, but “the guy modifying his cars” in Cecil’s column used “electricity from the alternator to split water molecules,” so I don’t think he’s doing what you suggest.
Divorcing your idea from whatever the guy in the column was doing, though: there’s no reason something like you suggest wouldn’t work, and improve efficiency.
Yeah, a regular alternator wouldn’t work. You’d need a pretty heavy duty alternator or generator to create appreciable amounts of hydrogen. And you’d need to cut it off (either mechanically or electrically) when the vehicle was cruising or accelerating, and switch it on when you were decelerating or idling. All in all, it probably wouldn’t be worth it, or they would already be doing it. But you never know - where’s a mechanical engineer when you need one???
I see where you’re going here. Energy from braking, heating, etc… can be stored as electricity in batteries, or converted to hydrogen, or spin up a flywheel, or heat molten salt (what some solar plants do). It’s all just a way to store what would have otherwise been wasted energy, and the putting it to use accelerating the car later.
But I doubt the “Brown Gas” folks are doing any of that. It’s just a doo-dad you put on your carburetor. Regenerative breaking isn’t something you just slap onto your car. Also, none of this would help with highway millage, which flies in the face of the trucker’s claim. It’s worth noting the Honda Prius is LESS efficient at highway driving (48 city, 45 highway) probably reflecting the higher fuel cost of moving at higher speeds due to more drag. Tractor trailers aren’t known for driving in a lot of stop-and-go city traffic.
One of the reasons that hybrids use electricity is electric propulsion and storage is safe, compact and well understood. We also have a cheap, (potentially) clean, nationwide electricity generation and transportation system. You can go home and charge up your car with cheap power to use less gas on your commute (at least it would have if the hybrid car makers weren’t so shy of being labeled an “electric car”, we have to wait a few more years for a mainstream plugin-Hybrid).
I don’t know about you, but I don’t have a hydrogen gas pump in my house.
I notice this seems to be talked about in reference to diesel engines.
Given that a big problem with diesel engines and efficiency is incomplete fuel combustion… adding an explosive gas to the air intake is basically making an Otto/Diesel hybrid. Depending on where in the compression stroke the Brown’s Gas finally ignites, how it effects the compressions stroke, or how it effects the combustion when fuel is injected, I don’t know… it seems like it could help.
There is no doubt that charging a battery is more efficient. But we aren’t just talking about that. A gas-electric hybrid has a battery and an electric motor, both of which add significant weight to the car. Electric generators can be 95% efficient in converting mechanical energy to electrical energy, while electrolysis is around 70% efficient. But if you can shave 500 pounds off a 2000 pound vehicle by not having a battery or electric motor, it might make up for it. Like I said - we need a mechanical engineer.
Probably the best way to actually do this would be to directly hook your “alternator” to the wheels–and we can call it a “generator” while we’re at it. Then you’re connecting the energy recovery device directly to where you’re recovering the energy from. However, it’s probably going to be more efficient to make hydrogen slowly (as opposed to quickly, in high volume, only when you brake), so what you want is a larger generator, and some batteries to store the excess recovered energy until you can use it.
Then you can use the stored electrical energy to make hydrogen whenever you want to. You could also use the generator as a motor, if you like. So this whole exercise turns into a stardard hybrid, but with the additional requirement of a hydrogen maker. However, you could now use the hydrogen whenever you want, irrespective of what the power requirement is at the wheels. That opens up some interesting possibilites, depending on your engine.
Overall, I doubt this scheme would be more efficient than a traditional hybrid electric. However, it could easily be more efficient than a traditional, non-hybrid vehicle. But you ain’t going to make a 30mpg Cavalier get 80mpg.
No. Combustion efficiency in diesel engines is over 98%, as Cecil notes in his column. “Incomplete fuel combustion” is most certainly NOT a problem with a typical engine, much less a “big problem.”
Actually, all of this brings up an entirely different question to me. Everyone seems to be championing fuel cells these days. Of course, fuel cells are hydrogen powered, which means that we will have to drive around with tanks of compressed hydrogen in our cars, and that filling a “gas” tank will be a much more elaborate process.
But fuel cells are expensive, they usually contain heavy-metal catylists, and (at least for the ones used in cars right now) they are only about 40% efficient. If people are willing to drive around with tanks of compressed hydrogen in their cars, and are willing to refuel at special stations, why aren’t we making cars that simply burn the hydrogen in an internal combustion engine? We have the technology to produce those kinds of cars right now.
Perhaps I wanted the word “ignition” rather than “combustion”.
Given there are 720 degrees (of rotation, 360 twice) in a four-stroke engine (0-180 intake, 180-360 compression, 360-540 power, 540-720 exhaust), you want all your fuel to burn between 360-540, yeah?
Just because 98% of the fuel burns throughout the cycle doesn’t mean that it burns in the most efficient manner. You could burn 100% of the fuel on the exhaust stroke and it wouldn’t do anything as far as making things go roundy-roundy.
In an ideal world you might want to burn 100% by 361. Or you might want it to burn along some profile that keeps cylinder pressure constant as the volume increases. Or you might want it to burn so you get peak pressures and maximum force around 440ish.
Just because 98% of it burns doesn’t mean it’s burning in the best way. What I’m thinking is that the Otto/Diesel hybrid thing could make the combustion profile more efficient in some way.
First of all, for optimum efficiency, you want your fuel to burn a bit after 360 (exactly when is a bit variable, because of heat transfer losses, but let’s say somewhere between 0 and 10 degrees after).
Second of all, engines hit pretty close to this mark. Here’s a description of combustions that include mass fraction burned curves. Note that for your typical spark-ignited engine, near 100% is burned by about 20 degrees after. Diesels do better than that.
Third of all, as you can see from the graph I linked to above, there is room for improvement. Controlled auto ignition (the area of study in the link) has a more efficient burn than a typical spark ignited engine. I believe (but this is not my area of expertise) that injecting hydrogen along with gasoline in the correct proportion with the correct timing will also give a more efficient burn.
Fourth of all, understand that although there is room to improve burn times, we’re talking about a few percent efficiency improvement at best. That’s interesting and perhaps worth going after, but you’re not going to see a jump in fuel economy to 80mpg as a result. Anyone who tells you so is either woefully deluded or a scam artist.
I would just like to say that I’m happy to see Cecil’s column on this subject. I’ve known that this “technology” is largely bunk for quite some time, but could never explain the why to friends who get all a-twitter over the ads.
No an alternator does not “waste” electricity. The alternator is a demand controlled system. It converts mechanical energy to electrical energy on an as needed basis. If your battery is fully charged, the car is idling with no accessories on, the alternator puts a very small drag on the engine as very little electricity is needed. If your battery is low, the high beams are on, the fan is on high, and the rear window defroster is on then the alternator is putting quite a bit of drag on the engine as it is converting quite a bit of mechanical energy to electrical energy.
Don’t feel bad, we have a customer that is designing a system to create hydrogen from water using the “waste” energy from the alternator. He got upset with me when I pointed out that this is not how an alternator works.
I know there are solar cells that are designed to slow charge car batteries that put out 12 volts at 5 watts. Would this be enough to catalyze water effeciently enough to produce a combustable product?
Sure it would only work in the daylight, but if the engine is sucking cheaply produced hydrogen and oxygen to suppliment the petrolium during the day wouldn’t this improve mileage somewhat (at least for us daytime drivers anyway)?
When I was a teenager, and slot cars were popular, I put a voltmeter across the connectors of a motor for one lying on the table and flicked the pinion between thumb and forefinger. The needle* on the meter jumped a moment, the direction depending on the way the pinion rotated. Intrigued, I put a six-volt flashlight bulb across the connectors and repeated the experiment. I got the faintest flicker of light, but more to the point, the pinion was noticeably more resistant to turning with the bulb as a load.
Fastening the motor down, I then put another motor opposite it so its pinion would drive the first motor-now-turned-generator. Cranking up the motor with a controller and 12 volts, I got the generator to light the lamp to a yellowish glow. I never did measure the voltage but I’d guesstimate it a five or five and a half volts. I would imagine the current was considerably less than the input current as well.
*Remember when meters had needles instead of digits?
