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| It's also a concept that, as you are finding, kinda works on the dusty corners of what is physically possible... Didn't they use the same principle for the power pods on Tatooine? Although, they must have had something more efficient than a Stirling engine for the generator. Melbourne found...

btrueblood, Oh, great. Now, I have a semipermeable membrane. That's funny, because I almost joked about moisture diffusion. Glass would be great, if only it were more transparent to infrared in the atmospheric window? Does Depot carry tellurium? I'll do the math and worry about materials later.

btrueblood, I've come to the conclusion that the group is hazing me.

Thank you, btrueblood! The required vacuum might be too high for practical materials, but you might not find the devices for sale for other reasons. Maybe there isn't a market due to maintenance reasons, susceptibility to bird droppings, roof rats, UV degradation of practical cover materials...

IRstuff, I did say something. The example for radiative output above gave 50W/m^2 net radiated output, at -18°C (38°C below ambient), using Smith's model for radiative cooling through an aperture of 30° and non-radiative losses of 1.5W m^-2 °C (loss estimate per Smith). You're stuck on the...

IRStuff, 200K is a dandy temperature, only 6.5K above the effective sky temperature in my example. I'll radiate at 253K and need a coat to stay warm. :) Who said anything about cryogenic temperature? Who said anything about 4K? You're not playing fair.

Chicokpee, I am still perplexed by your reasoning. What does the saturation pressure of water inside the volume have to do with condensation outside the volume, if dry gas *without water vapor* is ineffective at preventing condensation. Actually, the radiator should be the coldest part of the...

Okay, looking at it again, I misunderstood the answer to a question that I saw somewhere here regarding heat transfer in a container at reduced pressure. That answer led me to believe that convective coefficient would be the dominant factor. Looking at Nusselt, Rayleigh and Prandtl again, it...

Thanks, IRStuff, I was aware of the issue that you presented. Smith addresses radiative losses from the cover, but Smith was only looking at 10°C below ambient. Of course, as Smith admitted, non-radiative losses would be a large portion of total aperture assembly losses, and Smith suggested...

Yikes! I had been playing with the model with the same spreadsheet and lowered the non-radiative losses and dropped the cabinet and thermosyphon losses. At -18°C radiator temperature, net radiated output minus losses would be approximately 50W for a 1m^2 radiator. It still looks like passive...

racooke1978, Maybe I'm talking apples, and you're talking oranges. I thought that I described the device adequately for the purposes of the heat transfer question. I came up with the device before I found the patent. I'm just trying to verify the model. The patent defines a device for making...

Thank you, chicopee. I'm confused. That would address the volume between the radiator and the HDPE cover. However, that would be covered by replacing the volume in the cavity with dry gas, which is supposedly not effective at preventing condensation externally (atop the cover), when the cover...

racookpe1978, I apologize if my response above sounded somewhat snarly. I was trying to be humorous. Since the patent makes it clear that the invention is for terrestrial environments, I concluded that you hadn't read the patent, nor were you trying to be helpful. I have done the math with...

racookpe1978, you beautifully cynical bastard, We're not talking Stanley Meyer running a VW on water. Does the patent office give them a pass for being UofC and Argonne and the USA DOE? Why would the DOE want to prevent anything of this nature? I noticed something about a computer model, but...

The question relates specifically to US Patent 4624113, Passive-Solar Directional-Radiative Cooling System, University of Chicago representing Argonne National Laboratory on behalf of assignee, USA, DOE, 1986, in a 3D compound parabolic reflector assembly with a 3D compound parabolic housing, a...