I have an airtight container, the "hot-box", filled with air from outside. I close the two valves to the outside air, and let the sun heat it up. Once it reaches a certain temperature/pressure: I open/unlock a one-way check-valve that leads to a shaded/water-immersed coil of copper tubing. The tube is open to (indoor) air on the other end. For simplicity, let’s say the copper coil is long enough that hot & high-pressure air from the container, while passing through it, will be cooled to room-(outside)-temperature by the time it reaches the open end. When the air finally escapes from the tube, it will expand from high-pressure to atmospheric pressure, further cooling the gas. The amount of time it takes the hot-box chamber to stop pushing air (1atm), depends on the friction of air in the copper tube, and size of the hot-box. When the hot-box reaches 1atm, or close-to-it* (no longer pushing high pressure air); we close/lock the valve to the copper tube, and open the two valves (top and bottom) exposing it to open air so the hot air inside will be replaced with fresh air, and we can repeat the process. Is all of this actually correct? Am I forgetting/ignoring something important? Like; will significant pressure be lost due to friction in tube? Or, do I need to consider the air already in the tube if << the air in hotbox? If this does work, I assume such a device like this already exists, what is it called? ( I saw similar, but not the same, devices here, http://en.wikipedia.org/wiki/Solar_air_conditioning) If I wanted to use this as a small cooling unit (which would probably require a round-robin array of heating chambers, with temperature controlled valves for each, leading into to the coil, and so forth), will the cooling effect even be noticeable? Or should I be asking, how big or hot would my hot-box need to be for the effect to be noticeable? (I live in rural high desert: powerful sun, low atmospheric pressure, lots of space) I'm getting a bit lost trying to figure out what’s going to happen to the pressure in the hot-box chamber (and the tube's output), when the air is leaving via the open end of the copper tube, AND still being heated by the sun. E.g. will the decrease in pressure be linear, or exponential? *I think this info will be important in determining when a "cycle" should end, and the hot-box flushed with fresh air. Thanks in advance for your feedback!