Safety and thermal efficiency performance assessment of solar aided coal-fired power plant based on turbine steam double reheat

Abstract

A novel system of solar double reheat hybrid with coal-fired power plant is proposed in this study. Solar energy is employed to reheat the exhaust steam from intermediate-pressure turbine for raising inlet steam temperature of low-pressure turbine. Solar double reheat hybrid with a N600–24.2/566/566 supercritical coal-fired power plant is investigated. An all-condition mechanism model of the hybrid system is proposed and simulated by MATLAB/Simulink in both power-boosting mode and fuel-saving mode. The heat-resistant temperature limit and maximum permissible steam velocity of the low-pressure turbine are discussed in view of turbine safety. According to the simulation results, the maximum solar energy input for safe operation of the turbine is determined as 24,952 kW and 23,486 kW in the power-boosting mode and fuel-saving mode, respectively. Both the solar-to-electricity efficiency and the standard coal saving rate increase with the increase of solar energy input, but decrease with the increase of unit load. Moreover, the solar-to-electricity efficiency of the hybrid system in the fuel-saving mode is generally 2–3% higher than that in the power-boosting mode. In the fuel-saving mode, the highest solar-to-electricity efficiency of 35.17% and standard coal saving of 19.14 g/kWh are obtained with solar energy input of 23,486 kW under 40%THA for the hybrid system. Finally, operation suggestions of the hybrid system are proposed for a higher solar-to-electricity efficiency of solar energy.