There's also the relationship between the amount of electricity necessary to move the trains at a useful speeds/payload, and the H2 capacity of the fuel cells - current locomotives have diesel engines in the 3400-3500 kW power range.
https://www.greenandgrowing.org/is-water-vapor-a-greenhouse-gas/ Quote: There is no novelty when saying that climate change is still affecting our planet. Besides other types of pollution and greenhouse gases, there are some who are wondering: Is water vapor a greenhouse gas? Water vapor is the most abundant greenhouse gas on Earth. However, many experts discuss the extent of its contribution. Scientists used NASA satellite information to estimate the ‘heat-trapping effect of water in the air.’ Therefore, they confirmed that the role of the gas is a critical component of climate change. Moreover, the heat-amplifying effect of water vapor is so dangerous that it may double the warming events determined by high CO2 levels in the atmosphere.
Depends on the output of the fuel cell and its capacity. It also depends on if the H2 is stored as a liquid.
Infrastructure limits the overall size to that of current locomotives/rail rolling stock. You could conceivably store the H2 in tender cars following the locomotives. So, again, it depends on the output of the cells themselves and the operating characteristics of same - and in any case, 2H and 1O will only generate so much power, regardless of the cell design. You'll also need power to refrigerate the H2.
The train that's working so far seems to go OK, plus there are a couple of trains working in Germany, so I'm not sure that's a problem. You don't need to refrigerate the gas, it's liquified and stored in cylinders.
Maybe. There must still be lubricants involved for the moving parts. There would likely be a greater requirement for lubrication, due to the lack of such properties inherent in the fuel. Inevitably, molecules of the lubricant would be exhausted along with the water vapor.
When you say 'train' I think of 100+ coal cars behind 3-4 UP locomotives hauling thru the Rockies. That's -not- what they have. You -do- need to refrigerate the tanks as the H2 will boil and expand.
My bad. It's stored as a gas at high pressure. Well, I suppose you could have the same number of H-locos ... but ... we're not supposed to be using coal anymore ... 'cos global warming ....
The UK is intending to use hydrogen trains for a very small portion of the network where electrification is uneconomical. At the moment it's a gimmick because as mentioned hydrogen is nearly always made from hydrocarbon fuels, personally I prefer a biofuel solution for trains, boats and planes as I think this far more achievable with nuclear and renewables picking up the slack for grid and manufacturing until we can finally crack OTEC (If we ever do) the holy grail of renewable energy with built in energy storage. We can make fertilizers and plastics from sea water but the energy costs are crazy high it's going to take a century for the planet to go close to carbon neutral if we don't have a nuclear war first.
We still have to use energy to make the hydrogen before we can then use the energy of the hydrogen to do something, like make a train go. So that means that the hydrogen isn't so much an energy source, as it is a method of energy storage. And there's always going to be a not-insignificant amount of energy lost is the storage/conversion process. In summation- hydrogen isn't a free lunch.
Among other things Excess electricity from wind and solar could be used, or night time nuclear electricity
Wind and solar are hardly making a worthwhile contribution to the energy grid as it is. We're a long, long way from the point where we're getting "excess electricity" from wind and solar.
Well, i have heard many complaints that these produce all their electricity in narrow time bands and therefor their winds up being excess supply during certain periods
That's not the case. They generate plenty of usable electricity when the wind is blowing and the sun is shining, but they don't generate anything when there's no wind or sunshine. That's the complaint, among others.
If it isn't efficient it can't sell, then its doomed for decades or at least a century in the dust bin. That helps nobody, better to make an efficient system that could sell, and this isn't it...
We have to cut down greenhouse gases or we won't have a planet, in less than a century. If we have to subsidise renewable energy then so be it.