In 747, Emperor Xuanzong had a " Cool Hall " built in the imperial palace, which the " Tang Yulin " ( U���g ) describes as having water-powered fan wheels for air conditioning as well as rising jet streams of water from fountains.
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For purposes of air conditioning, the Han Dynasty craftsman and engineer Ding Huan ( fl . 180 CE ) invented a manually operated rotary fan with seven wheels that measured 3 m ( 10 ft ) in diameter; in the 8th century, during the Tang Dynasty ( 618 907 ), the Chinese applied hydraulic power to rotate the fan wheels for air conditioning, while the rotary fan became even more common during the Song Dynasty ( 960 1279 ).
