Solar Powered Water Electrolysis In Zero G: One Step Closer To The Final Frontier
A study published in Nature demonstrates the possibility of using solar power to split water in to hydrogen for fuel and oxygen for life support in zero gravity increasing the feasibility of space travel.
This was accomplished through a method of induced chemical decomposition called electrolysis wear by a compound (in this case water) is broken apart in to it’s constituent elements (hydrogen, oxygen) via passing an electrical current through it.
Launching combustible fuel in to space is an expensive and dangerous process whereas launching water from the ground is much less dangerous and costly, a smart move for any burgeoning space venture. Furthermore, if we can break apart water in to hydrogen and oxygen respectively not only do you get clean burning hydrogen fuel but also one of the most fundamental elements for life support (oxygen)
We may not even have to launch water from the ground. By mining abundant deposits of ice water from near-earth asteroids we can utilize this fundamental natural resource without having to siphon it from our precious ecosystem.
This would reduce the cost and work involved in re-fuelling orbital satellites by creating hydrogen fuel from water – a common preliminary goal among the first generation of asteroid mining companies such as Planetary Resources, Deep Industries and The Asteroid Mining Company.
Using water from asteroids to create fuel via electrolysis could also make the space around our planet more safe in several ways – by preventing satellites from becoming abandoned due to higher fuel costs and by redirecting and/or mining asteroids before they can hurl down to Earth.
So now the biggest challenge is figuring out how to split hydrogen dioxide in to hydrogen and oxygen in zero gravity.
However with that being said, space is not the only useful place for this new source of fuel. Hydrogen, unlike oil, is clean burning – meaning that it produces less greenhouse gases as a result of combustion. So along with being useful in outer space, so to would it make a good alternative to oil down here on Earth.
This particular experiment involved placing separately charged semiconductor photoelectrodes in to a water solution and setting the platform in free fall using something called a “drop tower”. The force of an object moving towards the ground during free fall is one of the easiest ways to simulate zero gravity. This is similar to the momentary weightless feel of a car accelerating over a steep a hill, or even more accurately – theme parks rides sharing the same name (drop tower).
During a process called photo-electrolysis photons from the sun are converted in to an electrical charge via their interaction with photo-sensitive semiconductors. The resulting electricity is passed between the two semiconductors via a set of wires at the top as well as through the water solution at the bottom.
This creates a circular charge circuit that breaks down the hydrogen dioxide (chemical name for water) in to hydrogen and oxygen through it’s interaction with the excess energy of electrons.
Since hydrogen has more electrons than oxygen hydrogen bubbles accumulate at the negative photo-electrode and oxygen bubbles accumulate at the positive photo-electrode. However in zero gravity these bubbles do not rise to the top of a liquid, instead remaining near the electrodes for the duration of free fall. This makes it difficult or even impossible to extract the two gases properly in outer space. Scientists were able to discourage the bubbles from “sticking” to the electrodes by carving tiny hexagonal pyramids on to the surface. However, because of zero-gravity the bubbles still remain in the liquid instead of rising to the top were they can be collected.
Scientists think they may be able to circumvent this problem in the future by turning the platform in to a centrifuge that spins in such a way as to form artificial gravity – not unlike proposals for the creation of artificial gravity in habitable space stations.
2001 a Space Odyssey
However instead of allowing people to walk on the outer walls of a spinning station the centrifugal force would help separate the lighter gas bubbles from the more dense water solution.
Another obstacle to streamlining this technology is the lack of a proper infrastructure for Hydrogen “gas stations”. So before this method can see the light of day we need to test the centrifuge and build structures for deploying it on a mass scale whether that be in space on Earth or both. Irregardless the drop tower experiment brings us one step closer to introducing a clean burning alternative to oil.