Energy efficiency

From Free net encyclopedia

For energy efficiency in relation to economics, see energy conservation

In physics and engineering, including mechanical and electrical engineering, energy efficiency is a dimensionless number, with a value between 0 and 1 or with times 100 given in percent. The energy efficiency of a process is defined as:

<math> \mathrm{efficiency} \ \eta = \mathrm{{power \ output} \over \mathrm{power \ input}} = W / energy </math>

where W is the amount of useful work done by the process (in joules), and "energy" is the quantity of energy (again, in joules) used to run the process.

Energy efficiency cannot within Newtonian physics systems exceed 100%. For practical purposes, the only energy conversion that is 100% efficient is the conversion of electrical energy to heat.

Loudspeakers have a very low efficiency under 2 percent.

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