Tom Jacobs is with USA Coil & Air, and can be reached at www.usacoil.com and has information on some of the new technology referenced near the end of the article.
Water and steam have been used to cool and heat air in finned-tube heat exchange coils almost since the inception of heating and air conditioning. Freezing of the fluid and the resultant coil damage have also been around for the same length of time. It is a systematic problem that many times is preventable.