View source for Power density

{{Short description|Power per volume}}
{{about|power per volume|power per unit mass|Power-to-weight ratio|power per area|Surface power density|power per frenquency|Power spectral density}}
{{More references|date=July 2020}}
{{Infobox physical quantity
| name = Power density
| unit = [[watt|W]]/[[meter|m]]<sup>3</sup>
| basequantities = kg·m<sup>−1</sup>s<sup>−3</sup>
| symbols =
| derivations = [[power (physics)|P]]/[[volume|V]]
}}

'''Power density''' is the amount of [[Power (physics)|power]] (time rate of [[energy transfer]]) per unit [[volume]].<ref>{{Cite book|last=Jelley|first=N. A. (Nicholas Alfred), 1946-|title=A dictionary of energy science|isbn=978-0-19-182627-6|location=Oxford|oclc=970401289}}</ref>It is typically measured in watts per cubic meter (W/m³) and represents how much power is distributed within a given space. In various fields such as physics, engineering, and electronics, power density is used to evaluate the efficiency and performance of devices, systems, or materials by considering how much power they can handle or generate relative to their size or volume.<ref>{{Cite web |title=Power density - Energy Education |url=https://energyeducation.ca/encyclopedia/Power_density |access-date=2024-01-25 |website=energyeducation.ca |language=en}}</ref>

In [[energy transformation|energy transformers]] including [[battery (electricity)|batteries]], [[fuel cell]]s, motors, [[power supply]] units, etc., power density refers to a volume, where it is often called '''volume power density''', expressed as W/m<sup>3</sup>.

In [[reciprocating engine|reciprocating]] [[internal combustion engine]]s, power density (power per [[swept volume]] or [[brake horsepower per cubic centimeter]]) is an important metric, based on the ''internal'' capacity of the engine, not its external size.

==Examples==
{{expand section|date=July 2015}}
{| class="wikitable sortable" style="text-align: center;"
! Storage material !! Energy type !! data-sort-type="number" | Specific power (W/kg) !! data-sort-type="number" | Power density (W/m<sup>3</sup>)
|-
| style="text-align:left;"| '''Hydrogen (in star)''' || [[Stellar evolution#Hydrogen fusion|Stellar fusion]] || 0.00184 || 276.5
|-
| style="text-align:left;"| '''[[Plutonium]]''' || [[Alpha decay]] || 1.94 || 38,360
|-
| style="text-align:left;"| '''[[Supercapacitor|Supercapacitors]]'''
|[[Supercapacitor|Capacitance]]
|up to 15000
|Variable
|-
| style="text-align:left;"| '''Lithium-ion''' 
|[[Lithium-ion battery|Chemical]]
|~250–350
|~700
|}

==See also==
*[[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)

==References==
{{Reflist}}

[[Category:Power (physics)]]


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