Hydrogen Storage &
Energy Calculator
Work out how much hydrogen a cylinder holds at a given pressure and temperature, and what that converts to in usable electrical energy through a fuel cell. Corrected for real-gas behaviour — hydrogen stops obeying the ideal gas law well before 350 bar.
This version calculates nameplate capacity under ideal handling conditions: gas at a uniform stated temperature, complete fill to the stated pressure, and complete extraction. For an estimate that accounts for fill heating, settled pressure and unusable residual gas, see the real-world version.
Part 1 — Storage
Real-gas cylinder state
Pick which quantity to solve for. The other three become inputs. Hydrogen is far from an ideal gas at storage pressure, so every result runs through the compressibility factor Z.
Volume must be greater than zero.
Mass must be greater than zero.
Pressure must be greater than zero.
Enter a temperature.
Input your ambient environment temperature here.
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Every quantity below is computed in base units: litres, grams, bar, °C. Z is a function of pressure and temperature only — it does not depend on volume, so volume solves explicitly while pressure and temperature need a bisection search.
Source of Z: Lemmon, Huber & Leachman (2008), Revised Standardized Equation for Hydrogen Gas Densities for Fuel Consumption Applications, Journal of Research of NIST 113(6), 341–350. All nine coefficients used here were checked against the published table and match it exactly. The paper states a density uncertainty of 0.04 % (k = 2) from 250 K to 450 K at all pressures, and agreement with the reference standard to within 0.01 % from 220 K to 1000 K up to 70 MPa.
What this assumes: a single uniform temperature, a settled equilibrium state, gas phase throughout, and that every gram is extracted. There is no fill heating, no residual pressure, and no dead volume.
Part 2 — Energy
What that hydrogen actually does
Convert stored hydrogen into usable electrical energy, or work backwards from an energy requirement to the hydrogen and cylinder you would need.
Mass must be greater than zero.
Use .
Fuel cells are rated on LHV
Load must be greater than zero.
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Heating value: 120 MJ/kg = 33.333 kWh/kg, lower heating value. Published LHV figures for hydrogen sit between roughly 119.96 and 121 MJ/kg.
Efficiency: a single scalar. There is no polarisation curve, no load dependence, and no balance-of-plant draw subtracted from the net output. Confirm against the Protium-3000 datasheet before relying on it.
Part 3 — Range reference
How far that hydrogen goes
A scale reference, not a vehicle specification. The consumption figure comes from the most efficient hydrogen prototype in Asia, so treat it as the physical ceiling — not as what a road vehicle will do.
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Source: Nakoela UI Team, Universitas Indonesia, Shell Eco-marathon Asia-Pacific and the Middle East 2025, Prototype Hydrogen Fuel Cell category, rank 1 — an Asian record.
Conversion basis: the m³ reference conditions under SEM regulations have not been verified. This file converts at 30 °C and 1 atm, matching ambient storage conditions. A 0 °C (Nm³) basis would give 5,874 km/kg instead — about 11 % lower.
Part 4 — Gasoline comparison
The same energy, in litres of petrol
Read the small print on this one. By default it compares net electrical output against the raw chemical energy in gasoline — deliberately, and not a like-for-like comparison. The toggle applies a typical engine efficiency to the gasoline side.
How this calculator works
Calculations use the NIST-traceable hydrogen density correlation of Lemmon, Huber & Leachman (2008); the nine coefficients here were checked against the published table. Gasoline energy density (~8.9 kWh/L, LHV) is cross-checked across three independent sources. Cylinder sizes and the 350 bar working pressure refer to Spectronik Type III carbon-fibre cylinders — confirm current specifications against the product datasheet before relying on them for design. This tool is provided for guidance and estimation; it is not a substitute for system-specific engineering verification.
What this model assumes
One uniform temperature. A settled equilibrium state — there is no time variable anywhere. Gas phase throughout, with no phase check. Complete extraction: every gram counted, no residual pressure. Cylinder volume treated as fully available to the gas, with no correction for liner, valve or dead volume.
Validity limits
The Z correlation carries a density uncertainty of 0.04 % (k = 2) from 250 K to 450 K at all pressures, rising to 0.1 % below 250 K. Every scenario in this tool, including 700 bar, sits inside that band. Agreement with the reference standard is quoted separately as 0.01 % from 220 K to 1000 K up to 70 MPa. The real-gas correction matters above roughly 100 bar; below that the ideal gas law is close enough. Solving for pressure or temperature can return values outside the correlation range — the tool does not stop you, so read those numbers with that in mind.
Sources
Z correlation: Lemmon, Huber & Leachman (2008), J. Res. NIST 113(6),
341–350. Coefficients verified against the published table.
Hydrogen LHV: 120 MJ/kg. Published values cluster at 119.96 MJ/kg.
Range reference: 528 km/m³, Prototype Hydrogen Fuel Cell category, first place
and an Asian record — Nakoela Team, Universitas Indonesia, with Keris Hydro I, Shell
Eco-marathon Asia-Pacific and the Middle East 2025, Qatar, 8–12 February 2025.
Reference routes: the five distances are great-circle, not road distances. Road
distances run roughly 20 % to 40 % longer, so read the route multiplier as a scale
reference rather than a journey.
Gasoline: 8.9 kWh/L LHV. Published figures range from about 8.7 to 8.9 kWh/L
depending on the density and blend assumed.
Cylinder sizes and the 350 bar rating: confirm against the current Spectronik
product datasheet before relying on them for design.
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