Thermodynamic and economic analyses of a parabolic trough concentrating solar power plant under off-design conditions

Highlights: • Detailed model of air-cooled parabolic trough concentrating solar power was built. • Off-design performances under typical meteorological conditions were investigated. • Summer power generation decreased by 1.38 MW because back-pressure rose to 11.1 kPa. • Optimal design back-pressure was 5.0 kPa when feed-in tariff was 16.6 ₵/kWh. • Optimal design back-pressure was not sensitive to cloud factor in range of 0.6–0.8. -- Abstract: As concentrating solar power technologies progressively move to maturity, large-scale concentrating solar power plants have elicited increasing attention. The thermodynamic simulation and economic analyses of a 50 MW parabolic trough concentrating solar power plant in northwest China were conducted in the present work. The effects of meteorological conditions, including direct normal irradiance and ambient temperature, on the off-design performances were investigated by simulation calculations. Furthermore, economic and sensitive analyses were conducted based on the annual simulation. Results show that the back-pressure of air-cooled condenser fluctuated with both ambient temperature and power generation. The power generation of summer and autumn days would decrease by 0.53–1.38 MW for the rise of condenser back-pressure. The clouds mainly affected the molten salt level of hot tank in thermal energy storage. In the economic analysis, with the decrease of the feed-in tariff from 16.6 ₵/kWh to 8.6 ₵/kWh, the maximum total net income dropped from 6.65 M$ to 2.43 M$. The optimal design condenser back-pressure rose from 5.0 kPa to 5.5 kPa. Moreover, the optimal design back-pressure of air-cooled condenser was not sensitive to the cloud effect in certain range, but the total net income had a sharp drop from 7.37 M$ to 4.95 M$.