cepheus said:
The only economic way of producing hydrogen is via steam reforming from natural gas so unless you sequester the CO2 it doesn't even reduce greenhouse gases. At least electricity can be sourced from nuclear and renewables for all their problems. So what's the point?
No it isn't. Electrolysis is a very common process, and while more expensive than steam reforming, it is still very economical. It is also extremely likely that future nuclear power plants will abandon the rankin cycle and operate using thermochemical cycles which produce hydrogen directly. Future technologies such as photochemical and photovoltaic electrolysis are good candidates for hydrogen generation as well.
On another note, no way does a diesel powered bus produce less pollutants than one that is H2 powered. That article may state that, but I've read half a dozen more that state the opposite. I'll try and find some of them later.
Fuel cells do have limited life spans in relation to vehicle life. The membranes degrade over time. Google 'fuel cell stack poisoning'.
Membrane degradation is really no longer an issue with FCs. There's a variety of flavors of Nafion that easily exceed DOE targets. Poisoning isn't a real big issue anymore either assuming the hydrogen is relatively pure. The only real poisons that need to be considered are sulfur based compounds commonly generated by diesel engines, i.e. H
2S. Right now, the most dominant PEMFC degradation mechanism is the cathode catalyst layer which suffers from Pt particle agglomeration and dissolution.
How many labor hours are required to handle the receiving and storage and removal of H2 bottles for such an operation?
I don't understand? Why would you ever remove a H2 tank from a vehicle unless its being serviced? It only takes a few minutes to fill a 4kg H2 tank from empty to full in a FC vehicle (I've witnessed it first hand). Back to the OP question,
From what i understand, the only thing that makes using fuel cells in cars versus lithium batties less desirable, is the cost of hydrogen.
It's actually much more than this. The #1 advantage of using PEM fuel cells for vehicles is it allows for a completely closed chemical cycle. There is no other technology that can do that although some bio-diesel schemes aren't to far away from it. The other distinct advantage over batteries is that FCs are engines, not energy storage devices. Transportation requires an energy scheme which allows a vehicle to be able to travel from point A to point B with little to no downtime, aka charging a battery. You can however just swap a battery out and replace it with a charged one but then you create a logistics nightmare which would most likely come with severe cost penalties. Another aspect is that hydrogen is an incredibly versatile fuel. It can be made efficiently in a variety of ways and on any scale. Theres no reason you can't economically generate H2 from solar panels at home and still be able to fill up at fuel station if your taking a road trip.
So now for the real question, why aren't we driving FC vehicles today? In a nutshell its because of the scarcity of platinum which is the primary material used for the anode and cathode catalyst of PEMFCs. If Pt was cheap and plentiful, we would all be driving fuel cell powered cars today. About 75% of the cost of a FC stack (batch production) comes from the price of Pt, and its only getting more expensive. In order to solve this problem there is an enormous scientific effort to discover new catalyst materials in order to reduce costs and at the same time increase durability. A lot of scientists are looking at materials that are N or Fe based complexes to replace Pt, but so far most materials provide to low of an activity. But the prospects are looking pretty good and its very likely better catalyst materials will be discovered in the next few upcoming years. Toyota, Honda, GM, and I believe Nissan are all planning on releasing FCVs for commercial sale before 2015. Germany, Japan, and Iceland are already developing hydrogen infrastructures to support this new technology.