Power plant operation

• Rankin e-cycle with reheat to reduce the formation of water droplets in turbine, and to increase the efficiency of the cycle.

• In order to maximize the efficiency of a steam power plant it is desirable to operate as high a temperature as possible in the super-heater. However, above about 650oC various forms of metal fatigue become significant due to very high temperatures and pressures that the walls of the boiler tubes have to withstand.

• A typical 500 MW coal-fired plant consume around 250 tones of coal an hour.

Efficiency of Thermal Power Plant

• The efficiency of a Rankin e-cycle is usually limited by the working fluid. Without the pressure reaching super critical levels for the working fluid, the temperature range the cycle can operate over is quite small: turbine entry temperatures are typically 565°C (the creep limit of stainless steel) and condenser temperatures are around 30°C. This gives a theoretical Carnot efficiency of about 63% compared with an actual efficiency of 42% for a modern coal-fired power station.

• The power output or capacity of an electric plant can be expressed in units of megawatts electric (MWe). The electric efficiency of a conventional thermal power station, considered as sale able energy (in MWe) produced at the plant busbars as a percent of the heating value of the fuel consumed, is typically 33% to 48% efficient.