Since fuel cells create water as a byproduct wouldn’t a hydrogen economy just switch what greenhouse gases we are producing? It has taken about 250 years of constant fuel from coal, oil, natural gas and automobiles to push the ppm concentration of CO2 up by 100 ppm from about 280 to 380. Is the effect of fuel cells on water vapor levels too negligible to actually do any climate damage? Or would it not matter since we’ll probably be getting the hydrogen from water anyway and just readding it to oxygen in the fuel cell to get the original water back? What if we get the hydrogen from fossil fuels then combine it with oxygen, will that affect the climate in anyway or are the levels of new water vapor going to be too low to matter?
It will, of course, and contribute in a minor way to global warming. However, water vapor, while a major greenhouse gas, has one advantage over the other potential combustion products: a given portion of the atmosphere saturates with it, and when it exceeds the load level, it is precipitated out in liquid or solid form that is effectively non-polluting. You may have experienced the phenomenon.
Note that, of the other problem gases, CO2 is removed on a much slower cycle, being either taken up by plants or deposited as carbonate rock, and NOx and SO2 tend to mix with water vapor to produce acid rain and, at its worst, low-pH acidic watercourses. (Prince Brook, in the Town of Osceola, NY, at the height of the acid rain problem had a pH of 2.1 during spring runoff, about the same as concentrated acetic acid or standard-dilute HCl.
The point, of course, is that in some way, energy must be produced to meet human needs for it, and, save for nuclear and solar power and batteries, this is likely to result in combustion byproducts. Hence, the value of a hydrogen economy is that its combustion product is one the ecosphere already processes quite efficiently without harm.
That’s rain or snow, right? The way you put it, it almost sounds as if water is in some sort of dynamic equilibrium between the solid, liquid and vapor phases. :eek:
I remember a previous thread where it was calculated that the total sum of human contribution to water vapour paled in comparison to natural fluctuations.
I believe this is the point where someone makes the obligatory observation that hydrogen is not, in fact, a way of producing energy, so much as storing it. I guess that person is me, this time. To produce usable hydrogen, we either need to dissociate it directly from a fossil fuel, such as natural gas, which produces CO2, or electrolyze water, which requires electricity from some other source.
I asked a similar question and, IIRC the answer was that the water evaporating out of swimming pools was greater than would be produced by a hydrogen society.
And one extension of that point is that if you make hydrogen by electrolyzing water, you are removing the water from the enviroment before you replace it via combustion. If you get the H2 by alchohol reformation, then the plants you grew to make the alchohol similarly removed the water from the enviroment.
Another factor is that you don’t burn stuff in a fuel cell, you convert the chemical energy to electric energy without having to go through the ‘heat’ step in the middle.
Energy conversion from one form to another can approach 100% except from heat to another form, which has inhertant inefficienies and you are lucky to get 50%, much less in a car.
So in that context you will ‘react’ less hydrogen then if you burnt it in a IC engine., also since the heat is not necesserally needed, the water vapor formed can be condensed into a liquid.
