Specific power
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In engineering, specific power (sometimes also power per unit mass or power density) refers to the amount of power delivered by an energy source, divided by some measure of the source's size or mass. It is used to compare various power sources by a common figure representing their suitability for a particular role.
- Area: Wind turbines are often compared using a specific power measuring watts per square metre of turbine disk area (pi times the length of a blade squared). This measure is also commonly used for solar panels, at least for typical applications.
- Volume: When measuring a heat engine, specific power is typically quoted in horsepower per cubic inch of displacement, or alternately kilowatts per litre. The result offers a general idea of the engine's ability to efficiently extract power from its fuel. A modern high-performance car engine makes in excess of 1.65 hp/in³ (75 kW/L).
- Mass: When comparing batteries, specific power refers to the power-to-weight ratio, measured in kilowatts per kilogram. Various fuels are often measured the same way. This is also used as an alternate measure for solar panels, notably those used in space applications where weight is key.
