Surface power density
In physics and engineering, surface power density is power per unit area. Applications The intensity of electromagnetic radiation can be expressed in W/m2. An example of such a quantity is the solar constant. Wind turbines are often compared using a specific power measuring watts per square meter of turbine disk area, which is , where r is the length of a blade. This measure is also commonly used for solar panels, at least for typical applications. Radiance is surface power density per unit of solid angle (steradians) in a specific direction. Spectral radiance is radiance per unit of frequency (Hertz) at a specific frequency. Surface power densities of energy sources Surface power density is an important factor in comparison of industrial energy sources. The concept was popularised by geographer Vaclav Smil. The term is usually shortened to "power density" in the relevant literature, which can lead to confusion with homonymous or related terms. Measured in W/m2 it describes the amount of power obtained per unit of Earth surface area used by a specific energy system, including all supporting infrastructure, manufacturing, mining of fuel (if applicable) and decommissioning., Fossil fuels and nuclear power are characterized by high power density which means