Hydrogen is an energy carrier, not an energy source: you must first make it with electricity. The chain electricity → electrolysis → storage → fuel cell/power achieves an overall efficiency of only approx. 25–40 % — a battery achieves 90 %. Hydrogen therefore makes sense as a seasonal and long-term storage (summer surplus → winter), at larger quantities, or when you need chemically bound fuel (e.g. for engines). For daily backup power, batteries are the better choice.
2. Production: DIY electrolysisIn electrolysis, water is electrically split into hydrogen (cathode, −) and oxygen (anode, +). For DIY:
- Container + divider: collect H₂ and O₂ at separate electrodes — never mix the gases (oxyhydrogen!)
- Electrodes: stainless steel (V2A) works; nickel/platinum coated is more efficient
- Electrolyte: potassium hydroxide solution (KOH, ca. 20–30 %) conducts well. Never use table salt: it produces poisonous chlorine gas!
- Power source: 12–24 V DC, a solar panel with charge controller suffices for small amounts
Honest quantities: 1 kWh of electricity yields only ca. 150–200 liters of hydrogen (standard volume, ca. 13–18 g). 1 kg of H₂ stores around 33 kWh of chemical energy — that requires ca. 50–60 kWh of electricity. Small electrolysers deliver liters per minute, not cubic meters per hour.
3. Storage: the hardest stepHydrogen is the smallest molecule and diffuses through many materials (metal embrittlement, plastic permeability). Realistic options:
| Method | Advantage | Disadvantage |
|---|---|---|
| Low-pressure storage (gas bag, flushed container via water seal) | Self-buildable, safe (low pressure) | Huge volume: 1 kg H₂ ≈ 11,000 liters! |
| Metal hydride cartridges | Compact, safe (low pressure) | Expensive, limited capacity |
| Steel bottles (200 bar) | Compact, professional | Certified bottles + filling system only — no DIY! |
- Fuel cell: delivers electricity directly again (efficiency ca. 50 %) — expensive for continuous operation, but silent. Small air-cooled stacks from ca. 100 W available.
- Engine/generator: petrol generators run on adapted mixture (H₂ has different ignition/combustion properties, output drops ~15–20 %). Modifications = warranty loss, expertise required.
- Cooking/heating: technically possible, but flames are almost invisible — too risky indoors.
- Outdoors only — produce, store and use, never in cellars, tents or living rooms.
- Keep gases separate: never collect H₂ and O₂ in one container (oxyhydrogen 2:1!).
- Ban ignition sources: hydrogen needs extremely little ignition energy — static electricity suffices. Ignition range 4–77 vol.-% (wider than methane!).
- Prevent flashback: flame arrestor / water seal between electrolyser and storage.
- Hydrogen does NOT smell: without a detector you won't notice leaks — gas detector or soapy-water test on connections.
- ☐ Electrolysis cell with separate gas outlets (H₂/O₂)
- ☐ KOH electrolyte (20–30 %) + refill with distilled water
- ☐ Solar panel + DC source (12–24 V)
- ☐ Flame arrestor + water seal before the storage
- ☐ Low-pressure gas bag outdoors
- ☐ Gas detector (H₂ sensor) for the test area
- ☐ Fuel cell or adapted generator for use
- 1 kg of hydrogen contains as much energy as ca. 3 liters of petrol — but needs around 11,000 liters of volume at normal pressure.
- Island grids with hydrogen storage exist, e.g. on remote islands: summer solar surplus is stored and converted to electricity in winter.
- Hydrogen metal embrittlement destroys unsuitable steel pipes — V2A stainless steel or special composite lines are mandatory.