Why is the thermal efficiency of steam power plant low?

The efficiency of the steam power plant is low due to heat losses that occur at various stages of the plant.

The overall Steam Turbine Efficiency is quite low (about 29%) due mainly to two reasons.

Firstly, a huge amount of heat is lost in the condenser and secondly heat losses occur at various stages of the plant.

The steam turbine side uses the Rankine thermodynamic cycle with steam temperatures at saturated

conditions, which gives a lower thermal cycle efficiency than the high temperature coal fired power plants.

Thermal cycle efficiencies are in the range of 38%.