Resumen
Recent results are shown about the peculiarities of the pseudo-critical region, with special emphasis on properties important for energy production and conversion. The property-map of some materials, which are relevant as model fluids or as working / cooling fluids in energy engineering (argon, methane, water and carbon dioxide) and their relative positions to various adiabats ? influencing their stability through the anomalous properties ? are presented. Some potential technological problems related to the existence of these anomalies are discussed.