In 1974 Nobel Prize winners Rowland and Molina proposed that chlorofluorocarbons were stable enough to reach the stratosphere, where, under intense solar radiation they released chlorine atoms that could destroy stratospheric ozone layer protecting the earth’s surface from UV rays. This was confirmed by an extensive worldwide program that aimed at monitoring the ozone layer. As a consequence, a series of national and international agreements calling for the phase-out of the production, sale and use of ozone depleting substances such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) [3] were formulated. Another major environmental concern is the climate change also called global warming. Our planet is already facing the consequences of this phenomenon: polar ice caps melting, flooding from high precipitations, increase of the earth global mean surface temperature, plants and birds migration towards the poles, etc. The increasing awareness conducted to the Kyoto Protocol in 1997 [11]. The impact of a substance on the environment is characterized by parameters like ozone depletion potential (ODP), global warming potential (GWP), atmospheric lifetime (ALT). Table 1 lists environmental data for potential ORC working fluids. For the sake of a safety environment, the designers when selecting a working fluid for a particular application should insist on substances for which the ODP, GWP and ALT are as low as possible.