Power density (or volume power density or volume specific power) is the amount of power (time rate of energy transfer) per unit volume.
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.
Volume power density is sometimes an important consideration where space is constrained.
In reciprocating internal combustion engines, power density—power per swept volume—is an important metric.
Power densities of common materials
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||Specific power (W/kg)
||Power density (W/m3)
|Hydrogen (in star)