The Physics
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Energy Density of Hydrogen

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Zittel, Werner & Wurster, Reinhold & Bolkow, Ludwig. Advantages and Disadvantages of Hydrogen. Hydrogen in the Energy Sector. Systemtechnik Gmbitt. 1996.
Energy carrier Form of Storage Energy density by weight
Energy density by volume
Hydrogen gas (20 MPa) 33.3 0.53
gas (24,8 MPa) 33.3 0.64
gas (30 MPa) 33.3 0.75
liquid (−253°C) 33.3 2.36
metal hydride 0.58 3.18
120 MJ/kg
Bossel, Ulf & Eliasson, Baldur. Energy and The Hydrogen Economy [pdf]. 8 January 2003.
  Dimensions Hydrogen Methane
Density at NTP kg/m3 0.09 0.72
Gravimetric HHV MJ/kg 142.0 55.6
Volumetric HHV MJ/m3 12.7 40.0
142 MJ/kg
Thomas, George. Overview of Storage Development DOE Hydrogen Program [pdf]. Sandia National Laboratories, 9 May 2000.
Fuel Hydrogen weight fraction Ambient state Mass energy density (MJ/kg)
Hydrogen 1 Gas 120
120 MJ/kg
Ramage, Janet. Energy: A Guidebook. 1st ed. New York: Oxford University Press, 1983.
Fuel Heat Produced by Combustion
  kWh/kg GJ/tonne GJ/m3
Hydrogen 37 130 0.012
130 MJ/kg
Lin, Bruce. Bruce Lin thesis: Rules of Thumb. 13 September 1999. "Fuel and storage method energy densities
H2: 120 MJ/kg = 33 kWh/kg (LHV)
H2: 142 MJ/kg = 39 kWh/kg (HHV)"
120–142 MJ/kg

Hydrogen (H2) is a colorless, odorless gas that is the most abundant resource in the universe. On earth, it is mostly found as water. It is not usually found in its pure form because it combines easily with other elements. It can, however, be reproduced from renewable resources.

Hydrogen has one of the highest energy density values per mass. Its energy density is between 120 and 142 MJ/kg. This means that for every 1 kg of mass of hydrogen, it has an energy value of 120-142 MJ. It is highly flammable, needing only a small amount of energy to ignite and burn. Hydrogen burns cleanly. When it is burned with oxygen, the only by products are heat and water.

Today, hydrogen is mainly used as a feedstock, intermediate chemical, or specialty chemical. The US hydrogen industry produces nine million tons of hydrogen per year for use in chemical production, petroleum refining and electrical applications.

Currently, many people advocate a hydrogen economy, which will use hydrogen as an energy carrier or fuel. It can be safely stored and transported. Using hydrogen fuel would also improve air quality. However, since there are no naturally occurring sources of hydrogen, it must be made. The production of hydrogen is more costly than using fossil fuels. For now, NASA is the primary user of hydrogen as an energy carrier.

Michelle Fung -- 2005