Fans are inherently pretty inefficient. If you want to generate airflow across a surface, it's more energy efficient to move the surface than it is to move the

Fans are inherently pretty inefficient. If you want to generate airflow across a surface, it's more energy efficient to move the surface than it is to move the air (assuming you have negligible non-fluid friction, which trains do). Motors can be over 90% efficient. With a fan, you have the efficiency of the motor and then, on top of that, the static efficiency of the fan, which is often less than 50%. We use fans when it's not practical to move the things we want to create airflow over (which is the vast majority of the time). Otherwise, we use the object's own motion. This is the principle behind ramjets.