Cooling remains a critical bottleneck for parabolic-trough concentrated solar thermal power (CSP) systems in arid regions, where conventional wet cooling is constrained by water scarcity and dry cooling incurs substantial parasitic power consumption. To address this challenge, this work proposes an integrated bifunctional reflector structure for the parabolic trough collector system, in which a rear-side hydronic loop enables passive heat rejection via radiative sky cooling and ambient convection while preserving the reflector's optical role without requiring additional land. A two-dimensional distributed-parameter thermal model is established to capture the dominant radiative and convective heat-exchange pathways and is validated it against outdoor experiments on a dedicated unit. The validated model is then used to evaluate the thermal performance of the system under various operating and climatic conditions and to extrapolate its impact at the power-plant scale. The results indicate that the structure can deliver an average cooling capacity of 701.2 W/m2 under representative operating conditions, sufficient to meet the cooling requirements of power plant's condenser independently, consistent with the typical parabolic trough collector plants' operational context. A plant-level annual analysis indicates that under idealized assumptions of full-field deployment, sufficient cold storage, and continuous operation, the annual cooling supply can reach 191.7 % of the modeled demand, implying the potential to meet cooling loads while lowering condensing temperature. This suggests the bifunctional reflector structure presents a promising and economically feasible solution for improving the overall efficiency and sustainability of PTC power plants in demanding climates.