In energy transformers including batteries, fuel cells, motors, etc., and also power supply units or similar, power density refers to a volume. It is then also called volume power density, which is expressed as W/m3.
In reciprocating internal combustion engines, power density—power per swept volume or brake horsepower per cubic centimeter —is an important metric. This is based on the internal capacity of the engine, not its external size.
|Storage material||Energy type||Specific power (W/kg)||Power density (W/m3)|
|Hydrogen (in star)||Stellar fusion||0.00184||276.5|
|Supercapacitors||Capacitance||up to 15000||Variable|
- Surface power density, energy per unit of area
- Energy density, energy per unit volume
- Specific energy, energy per unit mass
- Power-to-weight ratio/specific power, power per unit mass
- Specific absorption rate (SAR)