Other Definitions of Efficiency

Based upon the nature of activity and the preferred outcome, various expressions are used to associate the result to the input. Several of these are listed below as follows:

Task Efficiency:

It is the ratio of the hypothetical minimum input needed by the first and second laws to achieve some task to the real input for a specific means. In another form, it is the ratio of the real output to the maximum theoretical yield.  

Technical Efficiency:

It is the product of the translation efficiency at an intermediate step (when there is one) and application efficiency at the device which performs the helpful work; it is a measure of the helpful work completed as a percentage of the gross energy input.

Economic Efficiency:

It takes into account factors like the work expended in refining, extraction, and transportation of fuels, in the building and operation of energy translation facilities, power tools and electricity distribution networks, and in the handling of waste products and employment of ecological protection measures.  

Concentration:

In addition to the idea of energy quality, there is an extra intrinsic characteristic of energy source that might be defined as energy per unit volume or per unit mass for fossil fuels, and as energy crossing per unit area (i.e., energy flux) for solar energy. The other factors being equivalent, the higher transportation, storage and handling are simpler and cheaper.

Work Ratio:

A hypothetical power cycle might have a high thermal efficiency; still the real prototype might have an enormously low thermal efficiency. A warning of this possibility is specified by the work ratio, r_w :

Usually, it is big for Rankine power cycle and small for the gas turbine cycle.