Hydrogen bookings that account for pressure, not just kilos.
h2pass decides each refuelling on the physical state of the station: how much hydrogen there is, at what pressure, and how much will be produced before the requested time. If it falls short, it explains why with the figure and offers the first slot that works.
A second truck asks for 70 kg at 350 bar
The first one filled 70 kg at 10:00 and the electrolyser is running at 10 %. Move the arrival time.
- High-pressure bank at the end of the fill
- 359 bar
- Minimum to finish at 350 bar
- 380 bar
- Hydrogen stored
- 263 kg
Rejected: not enough pressure
The high-pressure bank would end at 359 bar and 380 are needed. 263 kg are still stored, but there is not enough pressure to complete the fill. First available slot: 13:00.
Prototype scenario E2, simplified: between 11:05 and 13:00 the pressure is interpolated between the two values computed by the simulator.
Why a calendar is not enough
A hydrogen refuelling station stores hydrogen in high-pressure banks and fills vehicle tanks in cascade: it starts with the low-pressure bank and finishes with the high-pressure one. To complete a fill at 350 bar, the high-pressure bank has to stay above 380 bar until the last kilo.
A single truck fill can drop that bank by more than 100 bar, and topping it up takes hours when production is low. If another truck arrives shortly after, the station may have more than 250 kg stored and still be unable to complete its fill.
With a calendar
The dispenser is free at 11:05, so the booking is accepted.
The truck arrives, gets 66 kg out of 70 and leaves with its tank not full.
With h2pass
The high-pressure bank would end at 359 bar, so the booking is rejected.
The driver gets the reason and books 13:00 in one click, when the fill does work.
How each request is decided
h2pass reads the station state at the moment of deciding, with data less than 5 seconds old. It then projects pressure and kilos minute by minute up to the requested time, using forecast production and earlier confirmed bookings. It answers in under a second.
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Station operational
No alarm prevents refuelling: compressor, dispenser and electrolyser are running, or there is enough stock to cover the fill.
If it fails:
RECH_ALARMA -
Dispenser free
Nobody else is using it during the fill or the 10 minutes of connection and disconnection.
If it fails:
RECH_HUECO -
Enough pressure
The high-pressure bank stays above 380 bar until the end of a 350 bar fill. At 700 bar, the dispenser booster needs banks above 200 bar.
If it fails:
RECH_PRESION -
Enough kilos
Stock, plus forecast production, minus earlier bookings: it has to cover the request with a 10 % margin.
If it fails:
RECH_KG
Pressure comes before kilos
That is what sets h2pass apart from a calendar: the case a calendar cannot see.
Every rejection offers a slot
The reason is given in plain language, with the figure behind it, together with the first slot in the next 24 hours where the same fill does fit.
Intention or firm booking
Drivers can say they will probably come, or book firmly. Only a firm booking reserves kilos; intentions help plan production.
Production follows the bookings
If stored hydrogen is not enough but production up to that time is, h2pass accepts the booking on demand: it reserves the future kilos and asks the electrolyser to produce more.
The next step is a planner that adjusts the setpoint every 15 minutes to the confirmed bookings and, for the same coverage, produces during sunny hours or when electricity is cheaper.
- From stock
- There are kilos stored at enough pressure. They are reserved for that driver.
- On demand
- Stock is not enough, but forecast production covers it. The booking is accepted and production goes up.
- Rejection
- Neither option works. The reason is explained and another time is offered.
It talks to the station the way it will talk to the real plant
h2pass never reads the simulator directly. Everything goes through the station controller (PLC) over Modbus TCP: bank pressures and temperatures, production flow, compressor and dispenser status, alarms and kilos dispensed.
When the truck arrives, it checks pressure and alarms again against the live reading, and only then writes the fill authorisation, hose and kilos to the controller.
Moving to a real station means changing the IP address and register addresses in the configuration. The booking logic stays the same.
| Register | Variable | Value |
|---|---|---|
| 30001 | Low-pressure bank | 301.4 bar |
| 30002 | Medium-pressure bank | 402.0 bar |
| 30003 | High-pressure bank | 465.2 bar |
| 30008 | Production | 7.2 kg/h |
| 30010 | Dispenser | free |
| 40004 | Authorised hose | 350 bar |
| 40005 | Authorised kilos | 70.00 kg |
Every frame read or written is stored with the real date, register and value in units, and can be exported to CSV. Every decision is stored with the rules evaluated and the reading that caused it.
Tested against a station with real parameters
The prototype runs against a digital twin of a hydrogen station in La Roda (Albacete, Spain): same electrolyser, same compressor and same dispenser. Where a figure is missing, the value is a documented, configurable assumption.
- Electrolyser
- 72 kg/h per stack, adjustable from 10 to 100 %
- Compressor
- From 20–40 to 500 bar, 360 kg/h
- Storage
- 3 cascade banks, up to 500 bar
- Dispenser
- 350 and 700 bar hoses
- H2 density
- NIST equation, not ideal gas (which is 33 % off at 500 bar)
- Mass balance
- 0.03 % error over a simulated day, measured with what the controller publishes
Roadmap
h2pass is currently a TRL 6 prototype moving towards a real station.
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2026 Done
Booking engine and station twin
Rejection for pressure, kilos, slot and alarm, with an alternative slot. Simulator with cascade banks and mass balance. Controller over Modbus TCP with a full trace.
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2026 In progress
Production driven by bookings
Electrolyser setpoint planner and a 30-day simulated campaign with more than 50 firm bookings.
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2027 Planned
Real hydrogen station
Connection to the controller of an operating station, users and fleets, payments, mobile app and AFIR data.
Do you run a hydrogen station or a heavy-duty fleet?
We are looking for stations and fleets to take h2pass to a real plant. Tell us about your case and we will show you the prototype running.