Functional principle of the ORC process
The thermodynamic cyclic process in essence resembles the one of the Clausius Rankine Cycle.
The working fluid is heated in the heat exchanger by means of the heat transfer medium (thermal oil or compressed water) of the intermediate cycle and evaporated (1 → 2). The superheated steam is then expanded in the turbine (2 → 3). The heat released in the context of the isobaric cooling of the steam is used to preheat the working fluid in the regenerator (3 → 4). The expanded steam of the working medium is cooled further and condensed in the condenser (4 → 5). The heat of condensation is either conducted away via cooling towers or used further as hot water for heating purposes. A pump re-increases the pressure in the working medium (5 → 6). After the working fluid has been preheated in the regenerator (6 → 1), the working fluid is re-evaporated in the evaporator and superheated. This completes the cyclic process. The difference compared with the Clausius Rankine Cycle is the incorporation of an additional heat exchanger, the regenerator, which is crucial for increasing the efficiency.