James, Use of steam for refrigeration was a standard technique early this century. AFAIR, steam was expanded through a nozzle and drew air from a venturi tube (?) creating a low pressure region with accompanying cooling. Old or complete air conditioning books would cover this - I have only seen it described once. The advantage is, as you note here, that you can convert available thermal energy into cooling. Also, there are no moving parts. You could also consider using a "kerosene fridge" type arrangement which uses heating to drive an adsorption cycle using, typically, ammonia and water. Only moving parts here are the fluid(s). This may be easier as the technology is current and common and you could copy an existing fridge or use an existing one and simply heat the appropriate point. Hilsch Vortex / Wiebel Rohr / Maxwell's ... typically seems to like around 100psi (7 bar / 700 kilopascal) but lower should work with suitable "design". Russell McMahon _____________________________ >From another world - www.easttimor.com What can one man* do? Help the hungry at no cost to yourself! at http://www.thehungersite.com/ (* - or woman, child or internet enabled intelligent entity :-)) -----Original Message----- From: James Newton To: pic microcontroller discussion list ; apptech@CLEAR.NET.NZ Date: Friday, 1 October 1999 03:48 Subject: RE: [OT] Second Chance. Maxwell's Demon and NOT Church of England. >I had a crazy idea some time ago, about using a small, cheap solar collector >to produce superheated steam (and my father and I did build the device >described up to this point and it works fine) and then use a venturi to >trade the velocity of escaping steam for volume of air moved (inject steam >via a fine pitot into the opening of a pipe so that outside air is pulled >into the pipe) and then direct that into a Hilsch Vortex to produce hot/cool >air for house A/C. > >I would guess that back pressure at the entrance to the Vortex would limit >the incoming air volume excessively or that the increased temp of the air >(due to the steam injection) would negate any cooling gains on the part of >the Vortex or some such other problem would prevent it from working. The >nice thing would be: No moving parts other than the water and the air and >the collector (sun tracking), automatically starts when the sun heats it up, >super low construction cost, almost zero operating cost (only maintenance >and water supply). >