Attn: Steven Chu, US Energy Secretary: Do NOT use WHITE.
http://climateprogress.org/2009/05/27/energy-steven-chu-white-roofs-geo-engineering-adaptation-mitigation/
Total Heat Reflection Using Microsphere Retroreflectors(THRUMRs) (thrumr pronunciation: like drummer but replace the "dr" with a "thr")
1. Reflect Heat Back to Its Source Like Traffic Signs Reflect Light
How Traffic Signs appear dazzlingly bright to cars at night:
1. Modern Traffic Signs reflect light back to the source of the light.
2. They do it with special, glass bead microspheres on their surface.
3. These microspheres "retroreflect" visible light back toward the light source.
4. The beads are transparent to visible light and have a high index of refraction.
5. The size of the beads and the high index of refraction cause "total internal reflection".
6. Since you are sitting behind your headlights (a light source), the sign appears very bright.
7. Traffic Sign glass beads are not transparent to broadband infrared and will not retroreflect heat.
2. If Traffic Sign microspheres Do Not Retroreflect Heat, What Will ?
Can We Create Heat Retroreflectors (Thrumrs) ?
1. What is heat ? Broadband Infrared Light
2. What is transparent to Infrared and has a high enough index of refraction ? Semiconductors,fused quartz...
3. Silicon, Germainium, Gallium Arsenide,... are well known materials with these properties.
4. Silicon is well understood so I will use it to refer to anything with the desired properties, hereafter.
5. Can we produce silicon microspheres ? Yes, there is a company producing spherical silicon photodiodes.
http://www.semiconductor.net/article/202583-Kyosemi_Uses_Ball_Diodes_in_PV_Modules.php
Thrumrs are simpler than these silicon sphere diodes since no electronic devices are necessary for retroreflection.
3. Would Thrumrs be Useful for GeoEngineering ?
Can Thrumr based applications limit or offset increased greenhouse gas concentrations ?
1. Thrumrs applied to roof surfaces is stealthy "white paint" on steroids.
a. Thurmrs are much more effective heat island reducers than diffuse reflectors like white paint..
b. Thrumrs send the heat back to the sun rather than toward your neighbors.
c. Many "white paints" absorb broadband infrared (heat) more like "black paint".
d. Thrumrs are typically dark to visible light so they do not adversely affect visible roof
colors.
e. Thurmrs reflect radiated building heat back inward in cold climates.
2. Thrumrs typically reflect visible light poorly and may work on or in glass or plastic windows.
3. Thrumrs can most likely be produced from waste silicon from the microelectronics industry.
4. Thrumrs look much like dark gravel or black sand and could be mixed with gravel on asphault shingles.
5. Thrumrs are chemically inactive similar to quartz sand. Quartz is a possible thrumr material.
6. Thrumrs are similar to sand as far as stray particles not likely to cause environmental problems.
7. Thrumrs might be used nearly anywhere radiative thermal barriers are desired.
8. Solid microspheres (whether glass or silicon) are cheaply produced using simple techniques.
a. Dropping molten material several stories to splatter out countless microspheres is the usual process.
b. The height largely determines the dominant droplet size and droplets of inappropriate size are immediately recycled.
© Bruce Waters 2009