That appears to be an Auxiliary Power Unit, or APU. In various forms, they are used as irrigation pumps, aircraft power units on the ground, and normal AC power generators. At a now-closed local airport, there were two Chrysler APUs that were powered by 392 Hemi engines. I saw these many years ago, and when I heard the airpark was being closed, I called the maintenance guy, who said they had already been sold...damn.