Seems like these should be widespread in cars by now. What’s the problem?
There are lots of problems. First of all, you do realize that they aren’t a source of energy, right? Think of them more as a battery. You still have to get the power from somewhere to make the hydrogen, and you never get as much out of it when you burn it as it cost to make, after you consider various conversion losses.
Some estimates are that it would take the equivalent of about 200 large nuclear plants to provide enough electricity to make the hydrogen necessary to convert the entire mobile fleet to hydrogen.
Then there are problems with safety. Hydrogen is explosive, and you have to carry a lot of it to get a reasonable amount of range. So one solution is to not store hydrogen in the car at all, but to make it from some other fuel ‘on the fly’. But this gets you away from zero emissions at the tailpipe, and still requires the burning of hydrocarbon fuels. This would in essence be another type of hybrid vehicle like the new Honda Civic hybrid and the Ford Escape HEV.
So Hydrogen isn’t a panacea. Its primary benefit is that it reduces air pollution in cities, because the conversion process back to electricity has pure water and CO2 as an exhaust.
But remember, these things still pump out CO2, so they aren’t a solution to the greenhouse effect, if that worries you.
My prediction is that you’re going to see rapid adoption of hybrid vehicles. It looks like the technology has finally caught up to the market place on those, and there are compelling reasons to buy them. The new Chevy ‘Contractor Special’ hybrid truck has a powerful V-8, gets something like 40 mpg, has great range, and has a really cool feature - the battery system allows you to convert the truck into a field electric generator for power tools. Just let the truck idle, and you’ve got a couple of 110V power plugs on the back that will provide 20KW of power as long as your gas holds out. The truck will probably be a diesel, so it’s just like having a diesel electric generator once you’re on the job site. What a great ‘freebie’ to get from converting to hybrid!
This answer confuses more than it enlightens me.
Nothing is a ‘source of energy’ - it all has to be made by something somewhere. Petrol has to be made from Oil, and Oil was made itself, in the distant past.
I have never heard of using nuclear power stations to generate Hydrogen - it is usually made by splitting methane (Natural Gas) with steam, and I don’t think anyone has ever claimed that we will be unable to make enough.
Hydrogen is explosive - correct, the whole point about an internal combustion engine is that its fuel is explosive. That means that Petrol is explosive as well! There are differences between the ways the two fuels burn, but hydrogen tends to escape and burn upwards, while petrol spreads out and burns sideways. In many cases this would make Hydrogen a safer fuel than Petrol.
Hydrogen is hard to store. This is one of the killer problems. It can be liquidefied, but only at low temperatures, which would have to be maintained whether the car was operating or not. Stored in gas form, you would need much larger tanks than petrol. You can store it chemically as a hydrate, but it would take a long time to fill a car tank up this way - it would be like re-washing the ion exchange column in your water softner. The Hydrogen could then be extracted as needed, but I have never heard of anyone proposing to make hydrogen ‘on the fly’. This would be remarkably inefficient. ‘Hybrid’ vehicles are usually ones with two forms of propulsion - such as battery electrics and petrol - and not ones where one fuel is burnt to make another. You may be thinking of some fuel cell techniques where a hydrocarbon like methanol is used to provide hydrogen, rather than pure hydrogen gas.
Only if something like methanol is used would there be any CO2 output. The use of pure Hydrogen will just result in water as a by-product.
As well as the fuel storage problem, the other killer problem is the cost of fuel cells. They use expensive elements like platignum. At the moment you can get more motive power cheaper using a petrol engine, and lean-burn petrol technology is lowering emissions considerably. So, unless petrol engines are outlawed, there is no compelling reason to dismantle our current petrol infrastructure and replace it with a hydrogen one.
CJB I’ll bet that you skipped a few science classes.
Combustion releases energy. Combine carbon with oxigen and you get energy. If you want to separate the carbon from the oxigen you have to put the energy back in. There are available sources of carbon and other fuels in nature but there are no available sources of free hydrogen gas. The only way to get hydrogen is to separate it from the oxigen in the water and to do this tyou need a lot of energy, that is the energy you get back later. So you are not getting any net energy, you are just storing energy you need to get from some other source in the first place. It is as if there was no free carbon in nature and all of it was already combined in the form of CO2.
In other words, if you had a source of pure hydrogen you’d be fine but H2O is worthless as fuel. It is already spent.
cjb’s eventual conclusion, that it’s a matter of the economics of switching powerplants (develop H2 fuel cells for cars vs. improve/hybridize the ICE), is still the basic answer to the OP, whatever scientific errors Pergau may have detected but neglected to point out explicitly. sailor’s more thermodynamic explanation still leads to economics.
If you have a true Hydrogen-Oxygen fuel cell, you do not have CO2 emissions at the fuel cell; but if you’re going to separate that Hydrogen without causing additional carbon emissions, you are going to have to crack it out of water using a lot of “clean” electricity – Sam Stone’s comment on power plants was referring to the equivalent energy requirement, NOT to that it HAD to be nuclear-fueled. As sailor said, H2O is “spent”, so the power has to be generated somewhere else. But while worthless as fuel itself it’s not worthless as a fuel source, just uneconomical. After all, you do need to put in a significant capital and labor expenditure between oil in the Earth and 91-octane unleaded at the pump, but the product value is enough to justify it.
My points about a ‘source’ of energy were really asides - I still think there is no fundamental difference between a fuel source and a fuel store - all of it is a cycle and the conservation of energy applies.
The OP asked about fundamental problems with Hydrogen fuel cells - I suggested that the problems were to do with Hydrogen storage technology, and fuel cell costs, so it’s not only economics. If fuel cells were mass-produced the price might come down, but we can’t store hydrogen as easily as petrol yet.
Incidentally, I skipped all science classes - my degree is in Philosophy.
>> I still think there is no fundamental difference between a fuel source and a fuel store
>> I skipped all science classes - my degree is in Philosophy.
Regarding the difficulties of hydrogen delivery – would it be possible/economically feasible to convert the ubiqitous natural gas pipeline network to deliver hydrogen gas instead of natural gas?
Other Issues Not Yet Mentioned.
Heat. The cells have to get fairly hot to run well. So that part of the car needs cooling, shielding, etc. Can pose a problem if the heat protection fails (causing fires). Int. comb. engines are hot too, but the shielding to hold the force of ignition in doubles as the jacket for cooling.
Susceptible to fouling. The fuel and air need to be exceptionally clean. And once fouled, the cell has to be replaced. A nastier issue than just changing your oil filter.
Note, as others have said, that while the total efficiency is not so good, at least the pollution sources can be concentrated to make pollution reduction more economical. So there’s an endless trade-off debate to be had there.
If you had practical methane fuel cells, it would be a whole new ballgame.
shelbo, I’m not much of a fluids guy myself (I’m um, actually a History major), but I know that the Alaska pipeline often ships different liquids by separating them with water.
I wouldn’t be surprised if it were possible to use the same concept to ship natural gas and hydrogen in segments through the same lines, by separating them with a noble gas or nitrogen which could be recovered in part and recycled. Still, you must isolate the nitrogen and/or noble gasses to begin with, and that too requres some sort of original energy source.
Ah, but not having the technology for efficient storage is an economic factor, cjb. Everything is an economic factor (heck, basic matter/energy conservation is economic: “you can’t get something for nothing”)
(Note: the previous was a deliberate hyperbole, before anyone jumps on me , OK?)
Well, yes. Fossil fuel IS a big energy ‘store’. It’s essentially concentrated solar energy. But it’s ‘free’ in the sense that WE didn’t have to put the energy into the system to create the store in the first place. It’s a gift from mother nature, minus the energy it takes to extract and refine it.
We have no equivalent natural sources of hydrogen. So if we want to use it as a fuel, we have to make it. And it always, always takes more energy to make than what you can get out - those pesky laws of thermodynamics and all.
Anyone who is seriously proposing moving to fuel cell technology MUST simultaneously propose a method for generating the electricity required to make the fuel in the first place. Anything else is disingenous (i.e. California’s electric car mandate, coupled with their hostility to new power sources, is an irrational situation).
That’s always been my complaint with advocates of hydrogen fuel cells. Often they are the same people protesting nuclear power and making it as difficult as possible for any new type of power generation to be built. They want to have their cake and eat it too.
But this requirement for more energy than you get out is why I said the main environmental benefit of hydrogen fuel cells was no to save energy, but to reduce pollution inside the cities. But the cities have been getting cleaner over the years, to the point where I don’t think air pollution is an issue that resonates the way it used to. People are more worried about global warming, or the economy. So the incentive to invest in hydrogen fuel cells may have diminished somewhat.
In the long term, one would think that the fact that fuel cells run on “produced” rather than “found” energy would be an advantage. At some point fossil fuels will run dry, and as far as I know we can’t make petroleum in the lab. (or can we?) By controlling energy (er, fuel) production as well as consumption we will, in theory, create a more sustainable system. Or at least one that doesn’t presume eternal found fuel sources, which I believe is the great flaw in our current system. The “freeness” of petroleum encourages us to overconsume.
Karellen, I think you skipped a few science classes too and you are mistaking many different things.
A fuel cell is a machine which converts one form of energy into another form of energy, just like the internal combustion engine. But you still need to supply the fuel which carries the energy.
Fuel cells change nothing as far as our sources of energy. They are just an engine with certain advantages (lower pollution, like electric motors) and certain disadvantages.
You can use hydrogen as fuel in fuel cells and in other types of engines but, since H is not free in nature you have to make it and you need a source of energy to do this. Hydrogen is just a storage medium, just like an electric battery. You have to put the energy in before you take it out, and to put it in you need to have it in the first place.
Hydrogen changes nothing in our need for energy, it is just a storage medium, like batteries. Our need for primary energy is not affected by fuel cells or by using hydrogen.