To effectively utilize the potential energy of cooling water, when dropping, conventionally discarded.

A water spray part 6 for cooled water and a filler unit 7 are arranged in a casing 2 having a blower 3 installed at the upper part and an exhaust port 4. A water collecting part 10 for drops of cooled water dropping from the filler unit 7 is installed between the filler unit 7 and a cooling water tank 9. A collective dropping water pipe 11 for the cooling water tank 9 is provided in the water collecting part 10. A generator 13 having a water turbine 12 for converting the potential energy of the dropping water into rotating energy is installed in the lower part of the collective dropping water pipe 11.