Energy Density Comparison: Hydrogen vs. Batteries
To compare the energy densities of hydrogen and batteries, particularly lithium batteries, we need to look at both their gravimetric (energy per kilogram) and volumetric (energy per liter) densities.
Hydrogen
- Gravimetric Energy Density: Hydrogen has an extremely high gravimetric energy density, typically ranging from 120 to 142 MJ/kg, depending on the measurement method. This is significantly higher than most conventional fuels, including gasoline and diesel, which have energy densities of about 44 MJ/kg.
- Volumetric Energy Density: However, hydrogen’s volumetric energy density is low. At atmospheric pressure and temperature, the density is about 0.010-0.011 MJ/L. To increase this, hydrogen must be compressed (up to 700 bar) or liquefied, reaching volumetric densities of 4.5-8.5 MJ/L under those conditions.
Lithium Batteries
- Gravimetric Energy Density: Lithium-ion batteries have a gravimetric energy density of approximately 250 Wh/kg (or about 0.9 MJ/kg).
- Volumetric Energy Density: The volumetric energy density of lithium-ion batteries is usually higher than that of hydrogen at atmospheric conditions, typically in the range of about 2-3 MJ/L, though this can vary based on battery design and type.
Comparison
- Gravimetric Energy Density: Hydrogen offers a much higher energy density by mass compared to lithium batteries, making it ideal for applications where weight is a critical factor.
- Volumetric Energy Density: However, due to its low volumetric energy density, hydrogen requires significant space unless it is compressed or liquefied, which adds complexity and cost to storage systems.
In summary, while hydrogen exceeds lithium batteries in energy density per kilogram, it lacks in terms of energy density per liter unless it is stored under high pressure or in liquid form. Batteries are often preferred in applications where volume is more of a concern than weight.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-do-the-energy-densities-of-hydrogen-and-batteries-compare/
