For moderate enthalpy heat sources, ORC cycles offer many advantages over the conventional steam cycle, primarily due to the simplicity of the turbine, the control system, and the balance of plant.
For an ORC, plant the turbine and piping sizes are smaller and thus less costly due to the fluid density differences. The condensing pressure in an organic cycle is generally above atmospheric pressurethus eliminating the need for complex vacuum and gas purging equipment that is utilized in a steam condensing cycle. Also, when the organic vapor expands in the turbine it becomes superheated or dryer, unlike steam, which becomes wetter during the expansion process. Therefore, superheating of the organic vapor prior to delivery to the turbine is not required. Further, since organic fluids have a low freezing temperature, there is no freezing in the condenser, even at extremely low ambient temperatures.
