Photonic Radiative Cooling
From Open Source Ecology
Basics
- Radiative Cooling that uses Technology within the Scope of Photonics to optimize their function
- Thus rather than a conventional reflective coating (or lack thereof), PRC coatings are added to enhance not just reflectivity, but also produce significant Black Body Radiation in the Midinfrared, which due to the Atmospheric Infrared Window goes through most of Earth's Atmosphere, essentially using Outer Space as the Heatsink
Methods
Research Level
- Multi-Layered Coatings and Photonic Crystals
- Complex to Fabricate/Apply; Typically similar to Semiconductor Fabrication
- May be of use for applications where reflectivity is inherently not possible, such as in solar cells according to This Paper ( "Radiative cooling of solar absorbers using a visibly transparent photonic crystal thermal blackbody" )
- Barium Sulfate
High TRL Methods
Novel Paint by High Density Pigment using CaCO₃ Microspheres
Microsphere Pigment Synthesis+Production
- Steps:
- Dissolve Each in Water, then Combining, this Forms the Pigment, byproduct of Sodium Chloride in Water Solution
- 5-30*c temp
- CO2 + Calcium Chloride = Calcium Carbonate (But in non-microsphere form); this complicates getting just microspheres from the reaction
- Citric Acid can be used to alleviate this, it produces Sodium Citrate when it reacts with the Sodium Carbonate, is easier to find, and
- 1 to 10 ratio for all solutions:
- For Example:
- 20g Sodium Carbonate + 200ml Water
- 10g Calcium Chloride + 100ml Water
- 3g Citric Acid + 30ml Water
- Citric Acid Solution is then Combined with the Calcium Chloride Solution
- 10-20*C Pre-mixing
- Sodium Carbonate is poured into the Calcium Chloride-Citric Acid Solution While Mixed in a Magnetic Stirrer or in a Blender
- Timer is Started at the moment of Pouring
- Containers can be cleaned with a mild acid such as food grade White Vinegar etc
- More Stirring = Smaller Particle Size (In Theory, Upper Limit + QC Needs to be Determined)
- Allow to Settle, Pour off Waste
- Multiple Batches of Varying Stirring can be made then combined to get that High Density Pigment. (In the video, they did 3x 1 Minute in Blender, 1x 5 Minutes in Blender, 1/3x 8-10 Minutes)
- Water Washes are done to Remove any Salts etc
- They made an odd Disposable Metal Baking Pan - Paper Towel - Printer Paper sandwich for the filter/drying step, investigating various other forms of drying that may scale better may be of interest (although kiss / if it ain't broke don't fix it, i guess)
- Contaminants can Supposedly Crystalize when drying, "locking in" microspheres into larger clumps
Paint Production
- 110ml (Dry) Acetone+12ml Water +10g Acrylic
- Acrylic Dissolves over days at stp, hours at ~43*c
- 7g of Pigment for Every 12ml of Paint Solution
- Acetone Evaporation Complicates Things (This wasn't addressed too much in the video besides a brief mention
- The "Dry Thickness" tends to be around a half of the wet/just applied coating thickness
- 0.5mm is the optimal end result
Internal Links
External Links
Temporary Trashcan
