Fanless is listed in Wiktionary, which gives an example from 1958, from the Anthony Burgess novel
The Enemy in the Blanket: "It was a good solid house, fanless but airy."
However the word was very seldom used until recent years, when it's being used to describe an electronic device with no fan to cool it down: "The newest, fanless Apple MacBook Air hits all the right notes..." (cnet.com, 1 May).
I couldn't find the word in any other dictionary, but it is a valid construction, with an obvious meaning. The earliest example I saw using the word in relation to sports fans was in the
Washington Post in 2003:
The decision to give a team to the Washington area is in the hands of the owners of the other major league teams. This oligarchy could relocate the fanless Montreal Expos to the District or Northern Virginia.
I'll add it as a rare word.