This study utilizes the piston wind generated by metro trains as an urban energy recovery source and establishes a comprehensive evaluation framework. A 1:5 scaled prototype was designed and fabricated using 3D printing technology, and its performance was tested in a self-built wind tunnel. Wind speed and electrical output were measured using an anemometer and a power meter to build a dataset and analyze the energy flow. Field measurements were also conducted in the Taipei Metro, where wind speeds were recorded during train arrivals and departures, with the peak measured velocity reaching 9.25 m/s. To prevent discrepancies between the scaled model and the full-scale system, a systematic energy performance analysis was performed. Tests under different wind speeds revealed that the prototype achieved a power coefficient of only 5.3%, significantly lower than the typical literature value of around 25%. Energy flow analysis showed that frictional losses accounted for merely 4.5%, while the primary loss was due to a low tip-speed ratio, causing airflow to bypass the rotor blades. Using dimensionless parameters such as the Reynolds number and Strouhal number, a scaling theory was developed. With an 11.6-fold increase in the Reynolds number, aerodynamic performance is predicted to improve substantially. The Strouhal number agrees with the Kármán vortex street theory, explaining the pulsed wind characteristics observed in tunnels. Based on the theoretical analysis, the full-scale turbine is expected to achieve a power coefficient of up to 35%. This work envisions future applications in metro tunnels worldwide, providing an innovative solution for sustainable urban energy development.