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Water quality: why the electrolyser needs de-ionised water

The water going into the electrolyser has to be far purer than drinking water. Getting it that way is a small but vital part of the system.

Why ordinary water will not do

Rainwater, bore water and town supply all carry dissolved minerals, salts and sometimes organic matter. They are harmless to drink but damaging to a PEM electrolyser, because ions in the water foul the membrane and catalyst and build up scale inside the stack. Over time that cuts efficiency and shortens life. So the system filters out particles first, then de-ionises the water to strip out the dissolved minerals.

What it would keep running

  • Sediment pre-filter
  • Carbon filter for organics
  • De-ionising resin or reverse osmosis stage
  • Conductivity monitoring
  • Returned fuel cell water in the loop

How de-ionising works

De-ionising usually combines a sediment filter, carbon to remove organics and chlorine, and an ion exchange resin or reverse osmosis stage that swaps or removes charged particles. The output is water with very low conductivity, which is the simplest way to measure how pure it is. The system watches that reading and can flag when a cartridge is getting tired.

Hard bore water with lots of minerals wears through resin faster than soft rainwater does. Telling the pilot team what water you have, and ideally sharing a water test, helps size the treatment properly so you are not swapping cartridges far more often than you should need to.

How it works →
The H2OME loop: an electrolyser splits water into hydrogen, the hydrogen is stored in a tank for weeks, a fuel cell turns it into electricity for your home, and the water returns to the loop.

How much water, really

About 9 litres of water go into each kilogram of hydrogen made. The fuel cell gives most of it back when it turns hydrogen into electricity, and that water returns to the loop. So the ongoing draw is the shortfall plus whatever the treatment stage rejects. For most rural tanks it is a small fraction of household use, though it is worth watching closely in a drought.

Questions

Can I use rainwater from my roof?

Yes, through the treatment stage. Rainwater is usually soft, which is easier on the de-ionising resin than hard bore water. Keep first-flush diverters and gutter guards working so less debris reaches the filters.

What happens if the water quality drops?

The system monitors water purity and is designed to flag when treatment needs attention. It should not keep making hydrogen from poor water, because that would damage the electrolyser. Replacing the spent cartridge restores normal running.

Does it waste water?

Reverse osmosis stages reject some water as brine, and filters need occasional flushing. The fuel cell returns most of the water used in electrolysis. The net use is modest compared with a household, but not zero.

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