Turbines for Open-Cycle Systems

After the droplets are removed, steam flows through large, low-pressure turbines, entering at a pressure of about 2.4 kPa. These turbines must be able to handle the large steam flows necessary to produce a significant amount of electric power. Studies by Westinghouse Electric Corporation concluded that the most reliable and cost-effective turbine for a 100-megawatt (electric) (MWe) (net) plant would be a low-speed (200 rpm) unit measuring 43.6 meters in diameter (Westinghouse Electric Corporation 1979), which requires more development. Multistage turbines used in nuclear or coal-fired power plants are already available. The low-pressure stages of these turbines typically operate at conditions close to those needed in an open-cycle OTEC plant. The rotor that makes up the last stage (which is typically about 5 meters in diameter) together with a modified stator can produce about 2.5 MW of electricity (gross) (Valenzuela et al. 1988). Larger plants will require either several turbines operating in parallel or major advances in turbine technology that will lead to larger rotors.