I recently posted on urban efforts to lighten surfaces, hoping to cool city neighborhoods.
Purdue University has developed the world’s whitest paint, that could help make more reflective and resilient cities going forward.
WEST LAFAYETTE, Ind. — In an effort to curb global warming, Purdue University engineers have created the whitest paint yet. Coating buildings with this paint may one day cool them off enough to reduce the need for air conditioning, the researchers say.
In October, the team created an ultra-white paint that pushed limits on how white paint can be. Now they’ve outdone that. The newer paint not only is whiter but also can keep surfaces cooler than the formulation that the researchers had previously demonstrated.
“If you were to use this paint to cover a roof area of about 1,000 square feet, we estimate that you could get a cooling power of 10 kilowatts. That’s more powerful than the central air conditioners used by most houses,” said Xiulin Ruan, a Purdue professor of mechanical engineering.
But you have to keep it clean of heavy pollen and dust a lot of places see.
They’re working on dry touchless cleaning for solar panels:
Waterless panel scrubbing would have been handy for the InSight Mars lander, which finally bit the dust, so to speak, at the end of last year. NASA was relying on wind to clean the panels, and make enough power to keep the electronics from freezing up over the winter, but that wasn’t enough, and after four years they lost contact. Curiosity uses a radioactive battery instead, which makes about ten times as much power, plus about twenty times that much waste heat, to keep its little brain cosy whatever Mars is throwing at it. It’s just ticked over eleven years, today, and still going strong.
Radioactive batteries are perfect for space probes and landers. I remember writing in to support the launch of the Cassini probe while clueless protestors drove their children hundreds of miles to protest the potential risk from the Cassini RTGs falling back to Earth in case of launch failure.
Most commercial buildings, particularly those built after about 1990 already have white rooves, albeit a rubberized membrane product very white on the outside while very black on the in (bottom). It improves (marginally) the efficiency of the air conditioning and the rubberized membrane is waterproof for the life of the building.
I’ve had this conversation with homeowners, who are loathe to even a light grey. That’s the conversation that needs to be had.
Well … and the roads
I never understood the aversion to a light color roof. Had to go back and forth with my wife about switching to light grey on our roof. Finally convinced her. But my logical complaint about this aversion was “How often do you actually bend your neck enough to see the roof?. About the only time you’ll see it is when driving home. What once or twice a day for seconds?” The benefit vastly outweighed those seconds. Just wished they had white solar panels back in 2013.
White solar panels ain’t gonna work – they need to absorb the visible light to make power, and they only do it at around 20-something % efficiency, so the rest ends up as heat. Leaves do their best by rejecting the green light they can’t photosynthesise so well, and using the rest of the spectrum. The result is that trees have a much lower albedo than PV panels, and don’t heat up nearly as much (plus they use evaporative cooling.) Of course, the PV panels use sunlight more efficiently, they’re just not as comfortable to stand next to.