Introduction The environmental concerns have risen the attention towards alternative energy conversion systems, exploiting renewable sources and waste heat recovery. Organic Rankine cycles (ORCs) represent an interesting option, especially in case of low-grade waste heat, for which the traditional steam Rankine cycles show a very low thermal efficiency [1-3]. Among possible ORC working fluids, some refrigerants have already been phased-out, whereas others (HFCs) will gradually disappear in the next future, according to the current environmental policy [4-5].