As an introduction to this masters thesis the general principle of steam thermal power plant is described. Power plant based on Clausius-Rankine's circular process is investigated with adequate methods to improve its efficiency. The thermal power plant from assignment is based on the Rijeka thermal power plant, whose modes of operation are described in the technical description. The main difference between the thermal power plant from assignment and the thermal power plant Rijeka is the number of regenerative water reheaters. The thermal power plant Rijeka has eight regenerative reheaters, while the thermal power plant from assignment has six regenerative reheaters. All other elements and principles of work are based on the thermal power plants Rijeka. Calculation of heat balance of the thermal power plant was performed, the steam generator balance and heat calculation of the steam generator. Flue gas emission was calculated, as well as the heat calculation of the steam superheater. A proposal for the reconstruction of the steam superheater was made and the analysis of how the number of regenerative reheaters affects the efficiency of the complete power plant. In addition, heat efficiency dependence on sea temperature was analyzed followed with analysis of flue gas emissions. At last, thermal scheme of a power plant was given, as well as a drawing of a steam superheater.