Green Hydrogen Storage vs Battery Simulator (2D)

Renewable surplus

Surplus power available 20 kW

Routed to electrolyzer 50%

10.0 kW → electrolyzer · 10.0 kW → battery

Release stored energy

Storage levels

Battery — 20.0 / 100 kWh

H₂ tank — 2.0 / 20 kg

Simulated time

Elapsed: 0.0 simulated days — fast-forward to watch battery self-discharge eat into idle storage while the hydrogen tank barely loses a gram.

Live round-trip efficiency

Battery in→out

–

H₂ in→out

–

Self-discharge lost while idle (battery only)

0.0 kWh

Electrolyzer ≈70% + fuel cell ≈50% → hydrogen round trip settles near 35%. Battery round trip settles near 90% — but only hydrogen can sit full for months with negligible loss.

How this mechanic works

Surplus renewable power (solar/wind generation that would otherwise be curtailed) can be split between two storage paths. The electrolyzer uses electricity to split water into hydrogen and oxygen (H₂O → H₂ + ½O₂), storing the hydrogen in a compressed tank; later a fuel cell recombines that hydrogen with oxygen to regenerate electricity. The battery stores the same surplus electrochemically and returns it directly.

Round-trip efficiency = electricity out ÷ electricity in, measured live from the moment you last reset the stats.
Hydrogen path loses energy twice — once making H₂ (~70% efficient), once converting it back (~50% efficient) — for a combined ~30-45%.
Battery path loses energy once, in resistive/chemical losses, for ~85-95% round trip — but a real lithium battery also bleeds a small amount of charge every hour just sitting there (modeled here), which the hydrogen tank essentially does not.

That is why grids favor batteries for daily solar/demand cycling, but reach for hydrogen (or other long-duration media) to bridge weeks or seasons — e.g. storing summer solar surplus to burn in winter.

Day 0.0

Renewable surplus Hydrogen path Battery path

Round-trip efficiency — battery vs hydrogen