Steam generation system operation optimization in parabolic trough concentrating solar power plants under cloudy conditions

Parabolic trough concentrating solar power with indirect thermal energy storage, as a promising application of solar energy, has been widely used in concentrating solar power plants. The exergy efficiency of thermal energy storage system and plant parasitic power consumption could change under cloudy conditions when the thermal oil distribution was adjusted to the live steam branch and reheat steam branch. However, the operating condition optimization of steam generation system has received insufficient attention. This study designed a detailed fixed-power-supply model of parabolic trough concentrating solar power plants to optimize the operation strategies under various conditions. The parametric constraints, which worked on the optimization, were investigated under various direct normal irradiation values. Simulation results indicated that the low reheat steam temperature, thermal oil mass flow rate of the live steam branch, and live steam pressure reduced the molten salt temperature at the discharging exchangers and plant parasitic power consumption. The distribution mode of preferentially satisfactory distribution of reheat steam branch demand had low molten salt consumption and high exergy efficiency of thermal energy storage. The molten salt consumptions under optimal conditions were 0.98%–13.68% lower than the consumption under original conditions with the decreasing direct normal irradiation from 300 W/m² to 210 W/m².