Technical options for organic rankine cycle systems

The plant components and the plant configurations adopted in the Organic Rankine Cycle (ORC) field differ appreciably from the solutions used in large steam cycles because of the different nature of the working fluid and the type of heat source. ORCs are rarely fueled by fossil fuels, they usually work at relatively low temperatures, and they are suitable for the exploitation of small available thermal powers. The possibility to choose a proper working fluid allows the cycle efficiency to be increased and also allows a simplification of the design of the main components (especially the expander). These peculiarities, make them the only technical option for the exploitation of medium-low temperature geothermal brines, biomass combustion, small solar energy power plants, and waste heat recovery from industrial processes. This chapter aims to present the key components installed in an ORC and the main cycle layouts used in commercial power plants, as proposed in the literature.