The problem is that it takes energy, electrical or chemical to make the hydrogen. These processes operate on a net loss basis. You will be creating less stored energy than you put in. It seems to me the only way this would work is if you can use the energy stored in the hydrogen more efficently than using the original eneregy source for the same job.

The rotary valve technology looks promising. Leave it to the domestic auto companies to allow someone else to lead the way. Seems they still have a not invented here mentality in a lot of areas. They should have done something with this long ago.

 

So, why not split the water on the car? We've got a 12v DC system in place already, water in the tank, do the electrolosis at the engine (where the carb or EFI is now) and burn it in the cylinders? Or is that too easy? I'm a Drafting Teacher, I don't know much about chemistry, so feel free to shoot me down!

 

It would be nice but you wouldn't get far. You're starting out with water, split it, burn (or fuel cell) it and finally end up with water again. Where is the energy coming from? It's coming from the energy you put into it to split the hydrogen and oxygen. So you have a net loss. It takes more energy to split the water and create the hydrogen than what you get from burning or the fuel cell.

 

 

Sure, you're operating at a net loss, that's what the laws of thermodynamics dictate. And yes, it takes less energy to get hydrogen from natural gas than from water by using heat and a catalyst. The problem is, you need a fossil fuel to start with, which has costs associated with finding it, getting it out of the ground to your facility, and polluting byproducts sooner or later as you follow those original molecules down the processing/consumption chain.

The nice thing about wind/solar electrolysis is that once the initial fixed cost is paid, the operating cost is low, and the energy source is free. And sure, you lose energy in the process, but you don't pollute to do it. There are now 1.5 megawatt wind turbines going up all over the midwest, and even if you could only operate at 30% efficiency (I expect it would be much higher than that), that's 300 000 watts of energy stored per hour the wind blows. More loss as the hydrogen is combusted or fed to a fuel cell on the other end, but to assume that the energy (originally solar) now stored in fossil fuels is cheaper is short sighted: hydrogen doesn't pollute, nor do solar or wind energy, and the economic cost savings by eliminating pollution needs to be considered...just ask California what it would be worth to them to have less polluting going on.

And yes, I meant "Challenger" shuttle. All I intended by bringing that up was to point out the explosive combustiveness of highly compressed hydrogen. (and yes, obviously we won't be burning it along with liquid oxygen in our cars either, so the effects of catastrophy wouldn't be as spectacular, not to mention that there would be a few less thousand tons of fuel involved ).

 

I agree we need much more wind and solar power as well as hydro (dams) and recovery of wave/tide energy. Problem is that even with all that built out to the max we still will not generate enough to stop using fossil fuels. If we greatly expanded nuclear power we could come close but that has its own set of problems.

The point I was making above was that fuel cells are only a battery. You have to put more energy into it than you get out. Listening to our president you get the impression fuel cells is a replacement for fossil fuels... not so unless you find a hydrogen mine.

 

Hydrogen can be burned in an engine. Mazda has a rotary prototype that does it very effectively. With out a "Hydrogen Mine" or some other form of getting large quanities of hydrogen efficiently we'll be using fossil fuels for a while.

 

So I take it from the replies that it would take more energy to extract hydrogen and oxygen from water than the engine would be able to make? How much energy will hydrogen release as it is combusted compared to gasoline? Is it not feasible to use elctricity from an alternator to split hydrogen and oxygen from water in quantities large enough to have a practical engine? I guess the whole trick would be getting enough hydrogen and oxygen into the combustion chamber to make enough power to run the engine. How much would be enough? I'm intrigued by this, but I don't have the proper knowlege of what is involved. How much hydrogen would 1 gallon of water yeild?

 

sorry, but there really IS no such thing as a free lunch. It will take more energy to split the water into hydrogen and oxygen than you will get back by combusting the hydrogen and oxygen at the other end...that's why the hydrogen needs to be produced outside of the car. Now if you had a "Back to the future" style "Mr. Fusion" generator in your car, then you might be able to carry around enough juice to make your own hydrogen

I can't remember my properties of ideal gasses, but 1 Mol of water (~18 grams) would produce 2 Mols of hydrogen, which would be something like 44 litres(??) at room temp/1 atmosphere (chemistry buffs feel free to jump in). A gallon of water would be about 9 300 liters worth of hydrogen at 1 atmosphere.

 

Running an engine on hydrogen is tricky because you need to store the hydrogen at an extreme pressure in order to carry enough of it with you to get any kind of range. The tank will be quite large and heavy.

You can't carry water and extract hydrogon in the car as it will take more energy to extract the hydrogen than you will make in the engine. When you burn hydrogen you get water. You can't start out with water and end up with water and get energy... there's no free lunch.

Fuel cells are more promising as they deliver more energy for the weight they use. But as I said before, a fuel cell is just a battery. You still need energy to extract hydrogen from water somewhere else. It's not a zero emissions vehicle as some like to believe. It is a remote emissions vehicle.

We need to start using renewable energy sources in earnest, but we will have a major energy crise coming up. Wind/solar/biomass/tide etc will never produce even the energy we use today. We either will have to come up with new energy sources or drastically reduce our consumption.

And just think what happens once the Chinese and Indians start expecting a similar standard of living as we enjoy. World energy demand will increase tenfold. All energy we don't have. I can see wars fought over energy not too far in the future.

 

I think you're right, 2mols H2 + 1mol O2 -> 2mol H2O. 2mols H2 hass a mass of about 4g (or to 2g from 1mol H2O) The actual volume would be 47.7L from 1 mol H2.

 

A fuel cell also would require a high pressure tank. I think the current range of a PEM fuel cell vehicle from a 1000 psi tank(don't remeber the volume) is 100 miles. I'm told that estimates of an IC engine (small I-4 or rotory??) from the same amount of H2 are closer to 300 miles.
Whatever they decide to do will be a major pain in the a$$ during the change over.

 

Fair enough. What I was thinking was storing the H2 as water, using some sort of "Hydrogen Carb" if you will, to split the water into H2 and O2 right on top of the engine and then feed it to the cylinders much the same way we do now with our a/f mixtures. That decription is really over-simplified, but it got me to wondering. Too bad it won't work. I'd love to just fill up with the garden hose...

 

GM is working hard on "The Hydrogen Economy" problem and are taking a top-down approach. They are looking at getting into everything from production to distribution and consumption. I have to give them credit, it's something they have really jumped into with both feet. I wouldn't be surprised if it turns out they are devoting the most money of any single group to hydrogen research. (that's just a hunch) They are looking beyond just using them in cars. One idea is to put them in houses. A byproduct of the electricity production is hot water so hot water production and even home heating come as a side bonus. Industrial applications are abundant. Places that use lots of power during peak times could generate power on-site to help offset demand. Hospitals, server farms, any place that needs backup power could now do so without the hassles of big honkin' diesel engines clanking around stinkin' up the place. GM's plan is very ambitous but (if you couldn't tell) I look forward to seeing what happens.

Natural sources like wind and water are interesting but like Markus said you'd need to devote a lot of production to just hydrogen. Nuclear is very interesting. There are processes inside certain reactors that produce hydrogen as a by-product. I believe hydrogen has a big place in the next few decades, not as a fossil fuel replacement, but as a supplement. There are a lot of problems with hydrogen as a fuel but it shows a lot of promise as well.

 

I am well aware of GM's research. My school has helped with a lot of it. The chemistry and and powertrain professors are always talking about it. GM has spent alot ore money on alternative fuels than any other company, hopefully can deliver on some of those promises soon. It will sure put a crunch on OPEC when hydrogen does get to new cars.