temperature heat source, and the Trilateral cycle efficiency equation
can be used for a non-isothermal heat source [7]. The Trilateral
efficiency is derived from the Carnot cycle efficiency and provides
an idealistic estimate where the heat source is utilised fully;
however, in many cases not all the heat available can be used. An
example is when the heat is supplied by exhaust gas where
condensation of sulphuric acid in heat exchangers must be avoided,
and another is when the cooler part of a heat source is needed for
heating purposes.