Solar thermal technology is a promising solution for decarbonizing heat production in industrial applications and district heating networks. When combined with heat storage and advanced control strategies, it can cover a significant share of heat demands. However, designing and optimizing such systems is complex due to their dynamic behavior and the interplay of multiple physical phenomena. To better understand and design these systems, modeling tools are essential. Modelica is particularly well-suited for this purpose. At Newheat, large scale solar thermal field models have been developed in the Modelica language using the Dymola environment. These models represent the thermal and hydraulic behavior of a solar thermal field at two different levels of complexity. Each is designed for different project phases-fast simulations for early-stage feasibility studies and slower but more detailed simulations for the engineering phase. To assess the accuracy of both models, comparisons with measured data on an operational solar plant were performed. Results indicate that both models achieve high thermal accuracy, with errors of less than 4% in annual heat production. On the hydraulic side, the detailed model provides more precise results than the simplified one. The main drawback of this model being slow simulations in case of very complex solar field layouts. Moving forward, these models will support various applications and enable scalable modeling of complex solar thermal systems, adapting to different project phases and requirements.