Hydrogen refueling compresses low-pressure delivered gas through multiple stages up to 700-900 bar for storage, then dispenses it into a vehicle's onboard tank. Rapid compression heats the gas (real-gas / Joule-Thomson effects), so dispensers pre-cool hydrogen to around -40°C to hit fill targets without exceeding the tank's thermal safety limit.
P V = z n R T (real-gas compressibility z != 1 at high P)
T_rise ~ compression_ratio per stage
fill_time ~ tank_capacity / (dispensing_rate * safety_derate(T))
- Compression stages — number of sequential compressor stages; more stages reach target pressure with less heat per stage.
- Dispensing rate — how fast hydrogen flows from storage into the vehicle tank once fueling starts.
- Storage pressure target — the high-pressure buffer tanks' set point (350/700 bar are common vehicle standards).
- Ambient temperature — hot weather raises the risk of over-temperature in the vehicle tank during fast fills, reducing the safe dispensing rate.
Because compressed hydrogen heats up as it's dispensed quickly, stations throttle flow rate (and pre-cool the gas) when ambient temperature is high, trading fill speed for a wider safety margin against the tank's ~85°C thermal limit.