Science and technology of the Tang dynasty
The inventor Ding Huan (fl. 180 AD) of the Han dynasty invented a rotary fan for air conditioning, with seven wheels 3 m (10 ft) in diameter and manually powered. In 747, Emperor Xuanzong had a "Cool Hall" built in the imperial palace, which the "Tang Yulin" (唐語林) describes as having water-powered fan wheels for air conditioning as well as rising jet streams of water from fountains. During the subsequent Song dynasty, written sources mentioned the air conditioning rotary fan as even more widely used.
Rider-Ericsson Engine Company
In his patent of 1759, Henry Wood was the first to document the powering an engine by the changing volume of air as it changed temperature. George Cayley was the first to build a working model in 1807. The Reverend Robert Stirling is generally credited with the "invention" of the hot air engine in 1816 for his development of a "regenerator" which conserves heat energy as the air moves between the hot and cold sides of the engine. Technically, not all hot air engines utilize regenerators, but the term hot air engine and Stirling engine are sometimes used interchangeably.