Even longer duration high altitude airships

Lockheed Martin has been recently exploiting the idea of using high altitude airships to perform long duration surveillance and communication relays here. Using very light photovoltaic panels, they plan to power an airship, eliminating the need to carry fuel on board. This allows the airships to stay airborne for a longer time. Currently they are planning to have systems that stay aloft for a minimum of a month.

It seems that their main problem for an even longer duration is the helium leakage. Although with modern materials they seem to have overcome the majority of the leakage problem, but there is still so much that the ships have to land once in a while (as far as I could figure, it was a month or two) to refill their helium.

One good Idea to extend the airships airborne duration is to replace the helium as it is lost, and although there is no source of helium in the stratosphere, we should be able to gather hydrogen at that height.

Before I go any further I would like to point out that by making the take-off and landing completely autonomous we can make the whole procedure very safe. I believe that the safety concerns of using hydrogen in unmanned aerial vehicles, although valid, have been too exaggerated, especially if the use of the H-gas would enables vehicles to stay aloft for literally years.

To obtain hydrogen we must first gather water from the air. This can be done using a cold plate in contact with the air. Much like the walls of a refrigerator the plate, when in contact with water molecules, will trap and solidify the molecules resulting in a layer of ice. Afterwards by heating up the plate the water can be collected and electrolysed into hydrogen and oxygen. The hydrogen can then be used to replace the lost gas.

Now all that remains is a question of numbers. For example whether the 15 KW solar systems on these demonstrative high altitude airships will be able to replace the lost gas? With 237 kj for one mol of hydrogen (20 liters at 1 atmosphere) I reckon it would be a close cut. Maybe I'll munch up the numbers next time. But I reckon that a wie bit larger airship can be set up to do this.