That's a good question.
But learning is not just about learning things from books. The knowledgeable person above is correct.
According to your logic, if the water falls to an altitude of 5,000 meters above sea level, if there is no resistance, how fast the water will reach the ocean? In addition, potential energy reflects the size of its energy through kinetic energy, and finally it is converted into other energy through kinetic energy. To put it bluntly, potential energy is a kind of potential that cannot be directly converted or transferred into other energy. or it is not the energy itself, it is man-made.
To put it simply, the reason water in your engine can circulate is because there is a water pump. The water pump is powered by a belt driven by the engine crankshaft. The power from the engine goes to the water pump, then the watergives energy to the generator, which is transferred twice depending on the energy transfer. . . If an external generator is used, the engine's power is sent to the generator through a belt and the energy is transferred only once.