Hydrogen storage and battery storage differ significantly in their energy density characteristics, particularly when comparing gravimetric (energy per unit mass) and volumetric (energy per unit volume) measures.
Gravimetric Energy Density (Energy per Mass)
- Hydrogen has the highest gravimetric energy density of any fuel, about 120 MJ/kg (or roughly 33.3 kWh/kg), which means it contains a very large amount of energy per kilogram.
- Batteries, such as lithium-ion, generally have much lower gravimetric energy density, typically around 0.5 MJ/kg to 1 MJ/kg (approximately 100-250 Wh/kg), far less than hydrogen on a mass basis.
Volumetric Energy Density (Energy per Volume)
- Despite hydrogen’s high energy per mass, it has a very low volumetric energy density:
- Liquid hydrogen stores about 8 MJ/L.
- Compressed hydrogen gas at 700 bar stores about 5.6 MJ/L.
- By comparison, gasoline—a hydrocarbon fuel—has about 32 MJ/L.
- Batteries store energy at much higher volumetric densities than hydrogen gas or liquid:
- Lithium-ion batteries typically have volumetric energy densities around 0.9 to 2.5 MJ/L (250 to 700 Wh/L), higher than compressed or liquid hydrogen.
- This means that hydrogen requires much more volume or special containment (high pressure or low temperature) to store the same amount of energy as batteries in a given space.
Summary Comparison
| Storage Type | Gravimetric Energy Density (MJ/kg) | Volumetric Energy Density (MJ/L) | Notes |
|---|---|---|---|
| Hydrogen (liquid) | ~120 | 8 | Highest energy per mass but low volumetric density; requires cryogenic storage |
| Hydrogen (compressed) | ~120 | 5.6 | High pressure tanks needed |
| Gasoline (for context) | ~44 (approx.) | 32 | High volumetric and gravimetric density |
| Lithium-ion battery | ~0.9 to 2.5 | ~0.9 to 2.5 | Lower gravimetric but higher volumetric density than hydrogen |
Hydrogen excels in energy per unit weight but suffers from low volumetric energy density, requiring bulky or energy-intensive storage solutions (compression or liquefaction). Batteries have lower energy per weight but higher energy per volume, making them more compact energy storage solutions in many applications.
In conclusion, hydrogen’s superior gravimetric energy density makes it attractive for applications where weight is critical, such as aerospace or long-range transport, whereas batteries are currently favored where compactness and volumetric energy density are more important.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-energy-density-of-hydrogen-storage-compare-to-battery-storage/
