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Also (as I recall; it's been decades) there were solar powered fan heater things that used complicated equipment to do basically the same thing that just lettin
by MarkusQ 1y ago
Also (as I recall; it's been decades) there were solar powered fan heater things that used complicated equipment to do basically the same thing that just letting the sunlight hit the ground (or maybe some black plastic) would have. I recall there being a lot of things that just ignored basic thermodynamics.
- hinkley 1y agoBlack bodies are tricky. What they readily absorb when the heat source is present, they will just as readily radiate back into the void when the source is missing. If you want to stay comfortable in a desert you wear white - keeps you cool in the day and warm at night.
- MarkusQ 1y agoExcept "black body" here is a technical term, and doesn't really correlate with "an object that's black". You could, for example, design something that absorbed well in the UV/visible/near infrared where sunlight energy peaks (sat, 250-1000nm) but has low emissive power in the far infrared of the ambient Martian surface temperature at or below the target temperature (say 2-100μm). Thus it would absorb a lot in the day but radiate far less in the night, all with no need for electronics, etc. The wind powered heaters (as I recall) had a similar issue; if the wind wasn't harvested to run heaters, it would have dissipated through friction with the ground, generating exactly the same amount of heat.
- hinkley 1y agoWind is caused by thermal gradients though, right? So you’re still moving heat from one place to another. Random placement, and you’d be correct. Not random placement would be a grey area.