hydrogen
gas hydrogenHydrogen physical properties. Direct combustion CO2 = 0 (no carbon in the molecule) — handled by the engine as an exact physical fact, NOT via an emission factor. NOT FOUND in DESNZ 2025 or IPCC 2006 (both are fossil/biomass-scoped). No upstream/production emission factor is included in v0.1 (grey/blue/green H2 differ enormously) — upstream is out of scope and must NOT be implied as zero.
- Direct combustion of hydrogen emits no CO2 (no carbon), but this is a COMBUSTION-ONLY figure. Upstream production emissions are NOT zero and depend entirely on the pathway (grey/SMR vs blue vs green) — they are not included here.
- Hydrogen's LHV and HHV differ by ~18% — always check which basis a hydrogen energy figure uses.
Density
0.08988 kg/m³
at gas at STP (0 °C, 1 atm)
Heating values
Emission factors
Not available. CO₂ and CO₂e factors are shown only when a cited source exists — never derived.
Worked example
Open in converter →Energy
Same energy expressed in other units.
Mass
Volume
Emissions
CO₂ and CO₂e are separate — never derived from each other.
Energy density
Energy per unit of mass or volume.
Assumptions
- density: assumed hydrogen density 0.08988 kg/m³ at gas at STP (0 °C, 1 atm)
- heating value basis: energy on LHV/NCV basis, 119.96 MJ/kg
- heating value basis: energy on HHV/GCV basis, 141.79 MJ/kg
Sources
- Pacific Northwest National Laboratory (PNNL) for the US DOE Hydrogen Safety Panel / H2tools.org
- National Institute of Standards and Technology (NIST), US Dept. of Commerce
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