ISSUE 19 ARCHIVE - HYDROGEN

Bill Borthwick

I like the word hydrogen; it rolls off the tongue and makes one think of clean energy and oceans blue. As a matter of fact the name of the element in Greek means “water-former,” which comes from its reaction to burning. Hydrogen is the most plentiful element in the universe, it has a molecular weight of 2, which makes it the lightest of the elements and production is comparatively cheap. Production is generally either done industrially through steam reformation of hydrocarbons or by other, more expensive processes, such as the electrolysis of water.

The benefits of using hydrogen energy are rightly widely touted; an energy source thats by-product is water sounds fantastic. Unfortunately the energy production is not yet efficiency increases, environmentally or economically, for hydrogen to be a major energy source at this stage. What this means is that the production of the gas, not to mention all the lithium based fuel cells, are expensive, and are more detrimental to the environment than just not using hydrogen as an energy source. Hopefully for all of us this may change in the future as efficiently increases, however the purpose of this article is not to bore you to tears about theoretical future energy production. So what, I hear you ask, is the point?

Well, O best beloved (hands up if you said Kipling) hydrogen is a wonderful gas for diving, which becomes a bit more pertinent when we consider that helium supplies are dwindling and therefore becoming much more expensive. Helium as an element is relatively rare. It is extracted from natural gas deposits, mainly in the USA, although other reserves exist in other parts of the world such as Qatar and Russia. It has a Molecular weight of 8, which is still much lighter than air (nitrogen's molecular weight is 28), but heavier than hydrogen. Helium is also a very good gas for diving, so let's compare the two.

Hydrogen is lighter, meaning it perfuses in and out of the tissue easier. Also it is easier to breath at great depth as the gas density is less. Both gases are highly thermally conductive, meaning that you can lose a lot of body heat just by breathing it.

Helium does create more communication difficulties and if you compress too quickly helium can produce a neurological effect (HPNS) and also at great depth helium can produce a narcotic effect on the diver.

Hydrogen is significantly cheaper to produce and more plentiful leading to lower costs and less of a carbon footprint. As you have no doubt deducted by now, hydrogen is a much better inert gas to use in a mix than helium. So why are we not using it? You guessed it, it goes bang.

The down side of hydrogen is that it becomes highly explosive in a mix with oxygen at around 4-74%. An added problem is that the energy required to create this explosion is incredibly low. Somewhere in the region of 19 micro-joules, to put that into context Ethylene requires about 85mJ to ignite and Petrol 450mJ. As any good tech diver knows the deeper you go the lower the mix percentage. It is possible to dive at depths requiring less than a 2% mix of oxygen meaning the explosive risk is negated, but it is a long breath hold dive to get down there and gas switching tables for these gases don't exist, as a matter of fact any hydrogen tables are very much experimental. Even still this doesn't address the real problem. Storing large amounts of oxygen next to large amounts of hydrogen to create the mix is dangerous.

Despite the obvious issues I think diving with hydrogen is possible and that all problems have a solution, we just haven't found them yet. So I turn to the diving community who are always up for a little test of ingenuity. Is it possible to modify a dive set to utilise hydrogen?

Could this be done with a breathing loop topped up with hydrogen stored safely in the form of a fuel cell or water to be electronically recovered to top up the diluent?

Could enough hydrogen be stored/recovered this way to undertake a dive of useful depth and duration remembering it's an inert gas?

Admittedly there would still be oxygen enriched gas in the breathing loop but as long as the sensors could be made intrinsically safe (no spark possible) then the risk would be negligible. It would negate to surface storage problems although it probably would lead

to bulky dive equipment.

Forgive the author of his ramblings; there are more problems than solutions in this article and a lot of questions as well. But maybe someone out there has enough of an interest and the right skill set to make this a possibility. Any responses to this article can be emailed. We love constructive criticism, but if you're going to sling mud at a problem, then please also chuck in a possible solution to clean it!