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Designing a new off-grid house around hydrogen storage

When the line company quotes a fortune to bring power up the road, off-grid stops being a lifestyle choice and becomes the sensible one. The storage question decides whether it works.

The storage gap

Off-grid houses usually have plenty of power on good days and too little in long calm or dry spells. Batteries cover a night or two, then a generator fills the gap. Hydrogen keeps for weeks without losing charge, so energy made by a wind turbine on a windy week or by micro-hydro after heavy rain can be stored and used in the flat spell that follows. That is the job this system is designed for.

What it would keep running

  • Whole house through a 15 kW inverter
  • Water pump from tank or bore
  • Heat pump and hot water
  • Workshop and garage

How it fits together

The turbine or hydro charges a 30 to 40 kWh LiFePO4 battery and runs the 25 kW PEM electrolyser when there is surplus, turning filtered, de-ionised water into hydrogen. When the battery runs low, the PEM fuel cell turns hydrogen back into electricity, and the water it produces goes back into the loop. A 15 kW hybrid inverter supplies the house. Round-trip efficiency is 30% or less. The generating source has to be sized for that loss, and the pilot would be honest about whether your site makes enough.

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.

Design the house for it

A new build lets you get the basics right before any equipment arrives: high insulation, a heat pump rather than resistive heating, an efficient hot water system and a plant room or outdoor space planned for the inverter, battery and electrolyser, with the hydrogen store outside. Consents, the building consent authority's requirements and the store's placement are part of the conversation from the first drawings, not an afterthought once the frame is up.

Questions

Can it fully replace a grid connection?

It is designed to run off-grid from wind or micro-hydro. Whether it can on your site depends on how much energy the source makes, because round-trip efficiency is 30% or less. That would be assessed honestly in pilot planning.

Do I still need a generator?

The aim is that stored hydrogen covers the flat spells a generator normally would. Whether that holds for your site depends on your source and storage, so keep options open until the pilot sizing is done.

What water does it need?

About 9 litres of filtered, de-ionised water per kilogram of hydrogen, and the fuel cell gives most of it back. On a tank-fed site that is a small draw, and treatment is part of the system.

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