Modernization of Existing Thermal Power Plants into Hybrid Solar and Fuel-Fired Plants

The major part of electric energy is presently generated by fossil fuel-fired thermal power plants operating according to the Rankine cycle. In the last decades, power technologies on the basis of solar concentrators (SCs) are becoming increasingly more attractive. The article shows the possibility of using heat obtained from solar energy (referred to henceforth as solar energy heat) at existing steam turbine thermal power plants (TPPs). A scheme for connecting an SC to the PVK-150 steam turbine power unit at the Tashkent TPP has been developed, due to which solar energy heat can be used instead of the heat obtained in the low- and high-pressure regenerative heaters (LPH and HPH) and also for partially replacing the heat from the economizer and evaporative heating surfaces of the existing steam generator. Calculations were carried out for different values of the solar energy heat share: in the range from 20 to 80%. Parabolocylindrical concentrators (PCCs) are used as SCs. A formula is proposed for calculating the solar energy into electricity conversion efficiency at hybrid solar and fossil fuel-fired TPPs constructed on the basis of existing steam turbine TPPs. The results obtained from modernizing the PVK-150 power unit by connecting an SC to it are presented. It has been determined in the course of investigations that, in using solar energy heat in the PVK-150 power unit for replacing the heat obtained in the regenerative feed water heaters, the solar energy into electricity conversion efficiency reaches 27.06 and 34.4% in the case of partial replacement of the economizer and evaporative surfaces of the existing steam generator with a solar steam generator.