Abstract: [Objectives]　Shadowing and blocking efficiency is a key parameter for the optical performance analysis and optimal design of heliostat fields, directly affecting the power generation efficiency of tower-type solar thermal power plants. Traditional calculation methods often lead to deviations in the optical efficiency calculation of heliostat fields due to their reliance on the assumptions of parallel mirror surfaces and simplified projection models. To improve calculation accuracy and efficiency, this study innovatively proposes a calculation method based on the vertex projection method.[Methods]　To realize optical calculations between non-parallel mirrors, the selected problematic mirrors are first projected onto the surface of the target mirror. Subsequently, dynamic coordinate system transformation is employed to accurately describe the relative positional relationship between non-parallel mirrors. In addition, a comprehensive efficiency loss evaluation method is established to fully consider the blocking and overlapping effects in multi-mirror systems. [Results]　In the comparative verification using a radially staggered heliostat field layout, the results obtained from the proposed method and SolarPILOT software show that the daily mean absolute error of shadowing efficiency is 0.84%, and that of blocking efficiency is 2.06%. Additionally, the blocking efficiency remains basically stable throughout the day, indicating that shadowing efficiency is the dominant factor affecting the shadowing and blocking efficiency. Moreover, the shadowing loss in the northern area of the heliostat field is significantly higher than that in the southern area. [Conclusions]　This study provides an efficient and accurate method for calculating the shadowing and blocking efficiency for the optimal design of heliostat fields.

Key words: tower-type solar thermal power, solar power generation, solar thermal power plant, heliostat field, vertex projection method, shadowing efficiency, blocking efficiency, mirror overlap