Leaky Hydrogen Fuel Cells Mean Holes in Ozone Layer

2 thoughts on “Leaky Hydrogen Fuel Cells Mean Holes in Ozone Layer”

1. The problem with the chlorofluorocarbons was that their chlorine acts as a catalyst for ozone destruction, so that even a small quantity causes trouble. The problem here is not one of catalysis by a small quantity, but perturbation of the whole stratosphere by a very large quantity of released hydrogen. That all depends on your estimates of how much we would release – as the article points out, we already release a huge quantity of hydrogen to the atmosphere, and replacing all hydrocarbon fuels would likely increase it by a factor of “four to eight”.

   The other issue is how long these atmospheric effects last. Cl in the atmosphere from chlorofluorocarbons stays there for decades; CO2 from burned fossil fuels is likewise in the atmosphere for a long time. But all the H2 is producing is a bit of excess water in the stratosphere – my guess is that turns over in at most a year, so if we notice a problem, and if we can find a way to quit releasing so much H2, the problem goes away in just a year – very different situation.

   All I’m saying is, there’s no way this should be taken as a huge roadblock to developing a hydrogen economy – something to keep in mind, yes, but it’s still far better than any alternatives.

2. Is it really true that a hydrogen economy is “far better than any alternatives”?
   Any?

   Compare hydrogen to something like aluminum. Both are combustible, and in fact the combustion of both serves to lift the space shuttle. Hydrogen gives the same energy from less combustible mass, but that formulation leaves out some important details.

   Hydrogen is easier to get from fossil fuels, being actually in them. If a hydrogen economy can include hydrogen from those sources, it can take an efficiency advantage from the shortcut that that provides. You don’t have to burn the fossil fuels, boil water,
   turn a turbine, turn a dynamo, rectify, and electrolyse other water; you can just
   steam-reform the fossil fuel. In a pur sang hydrogen economy, however, that advantage goes away.

   The important details left out include this: although per megawatt-hour of combustion potential energy, hydrogen is lighter than aluminum, on that same basis hydrogen-plus-oxygen is heavier than aluminum-plus-oxygen. Since rockets lift their oxygen rather than take it from air, this matters in rocketry.

   And this: in choosing between a fuel system that can deliver 1 kg hydrogen, and one that can deliver the equivalent 3.87 kg aluminum, recent work by BMW that shows that a kilogram H2 can be contained in 15.26 kg of of cryogenic tank should not be ignored. Compact, untouchy solids such as aluminum and aluminum oxide are containable in a steel bin that is 9 percent as massive as its contents. As a combustion energy reservoir, such a bin, when full, is a quarter as massive as its hydrogen counterpart. This matters in almost any application.

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