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What happens when the hydrogen storage runs empty

In a long enough outage any store runs out. Knowing exactly what happens at that point is part of planning for it.

The warning comes first

The system is designed to show the hydrogen buffer level and battery charge on its display, so running low should never be a surprise. As storage drops, that is your cue to cut back to the essentials: fridge, freezer, water pump, modem and a few lights. Reducing load stretches the last of the hydrogen much further than you might expect, especially if heating and cooking move to gas or wood.

What it would keep running

  • Essentials only as storage runs low
  • Battery carrying the last hours
  • Fridge and freezer prioritised
  • Water pump
  • Modem for news of restoration

When the buffer is empty

Once the hydrogen is used, the fuel cell stops. The 30 to 40 kWh LiFePO4 battery then carries the house on its own until it reaches its protective minimum, when the inverter shuts down output to protect the battery. At that point the house is dark, the same as any home without backup.

The system does not rely on hydrogen deliveries arriving by truck. It is designed to make its own fuel from water and electricity, so refilling waits for a charging source to return, whether that is the grid, a breeze for the wind turbine, or the stream flowing well enough for the micro-hydro.

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.

Refilling afterwards

When the grid comes back, the inverter reconnects, recharges the battery first, then runs the 25 kW electrolyser to refill the buffer, ideally in off-peak hours. With a wind turbine or micro-hydro scheme, refilling can start as soon as there is surplus power, even with the grid still down. Because round-trip efficiency is 30% or less, a full refill takes much more energy than the hydrogen gives back.

Questions

Can I buy hydrogen to refill it?

It is designed to make its own hydrogen from water and electricity, not to take deliveries. We will not claim compatibility with delivered hydrogen. Refilling comes from off-peak grid power, wind or micro-hydro.

Does running empty damage anything?

The battery is protected by its management system, which stops discharge before damage. The hydrogen side is designed to handle an empty buffer. After a long outage, check the display for faults once power returns.

How long does a full refill take?

It depends on how empty storage is, how much off-peak time your plan gives and whether wind or micro-hydro adds to it. The electrolyser is 25 kW DC, but a refill time for your setup can only be worked out during pilot sizing.

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