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). James Newton, webmaster http://get.to/techref (hint: you can add your own private info to the techref) mailto:jamesnewton@geocities.com 1-619-652-0593 phoneÊ -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Russell McMahon Sent: Thursday, September 30, 1999 2:22 AM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [OT] Second Chance. Maxwell's Demon and NOT Church of England. >I don't know if we are still continuing this prepetual motion thread,but it >occurred to me that one doesn't need a micro-machined piezo box to >"extract" energy from the thermal motion of atoms. What about a simple >resistor? Every resistor has a Johnson noise voltage present across it,and >if you had a perfect rectifier (or could place MANY resistors in series to >add up all the rms amplitudes of the noise),you should be able to rectify >this and charge capacitors with it. Thermal noise is AC and each resistor's signal is "very" random so placing N in series will not produce increased voltage as they are out of phase and will largely cancel. That said, if you can get a rectifier that itself makes less thermal noise and has a lower voltage drop than the resistor signal them you should be able to add them. Quite some rectifier spec, unfortunately :-). >That is, if you can violate thermodynamics. It DOES seem to me that both >this AND the piezo box would violate the requirement that, on average, >objects don't spontaneously cool,giving up energy the the ambient >environment. In fact,I thought that maxwell's demon did this as well. >Maxwell's demon was supposed to select out molecules based on their energy >WITHOUT itself using up any energy,right? No, Maxwell's demon doesn't violate Conservation of Energy (COE). [[Quick recap: The famed Maxwell pointed out that a gas contains molecules of widely varying energies - he noted that if one could obtain a friendly demon to select molecules of a desired energy range then you could obtain heating or cooling relative to the mean temperature of the gas. Strangely, he failed to realise that it IS in fact possible - sort of. Read on]] I've mentioned the Hilsch Vortex here before so will keep it really brief. Ask offlist if you want construction details. Basically, briefly and simplistically, air is injected tangentially into a tube so that it spirals at high speed. Highly energetic molecules tend to travel around the periphery, longer path, while lower energy molecules tend to spiral around an inner path. If you then provide separate exit holes for the inner and outer portions of the piraling gas you get cold and hot streams. You are not violating COE (no, no, not Church of England - no anti-religious spam please :-)) as the separation uses the energies of individual molecules to "assert" themselves in an environment where an energy gradient exists. However, there are losses in establishing and maintaining the vortex against tube resistance and turbulence. The amount of cooling is AFAIK rather less than you could get using other means (eg JT or turbo expander or Stirling/Piston expander or ...). The advantage of the demon is that he has no moving parts and costs almost nought to build (and is a type liable to be acceptable in eother type of COE environment :-)). >Sure, one can make a heat pump >which requires energy (which the vortex tube is, right?) as above, no. A heat pump is a "conventional" heat engine. >but AFAIK, no one >has ever made a device to extract useful energy from thermal motion without >using a cold sink, cooler than the source of heat. Yes, sort of. You can MAKE your own local sink en situ if you can cause your "coolant" to do work. I don't see that there is a conceptual difference between gas which is given energy by compression and gas having energy through thermal motion. Consider a turbo expander (turbine with gas expanding through it) or a piston expander (Stirling cryo-cooler). In both cases the expanding gas does work on "something" (here turbine or piston) and "gets cold" as a consequence. I feel that you should be able to allow gas particles to do work on something mechanically and the gas would cool as a consequence. If you could do this in an open environment heat would flow in from the surroundings to replace this. It would appear you were getting something for nothing. Any "real" thermodynamicists here to point out any errors? Someone mentioned Brownian motion in this general context. You can SEE dust particles driven upwards against gravity. Real work is going on here! regards Russell McMahon _____________________________ What can one unlimited energy seeker* do? Help the hungry at no cost to yourself! at http://www.thehungersite.com/ (* - or woman, child or internet enabled intelligent entity :-))