Computer simulations of Los Angeles show that resurfacing about two-thirds of roads and rooftops with reflective surfaces, as well as planting more trees, could cool the city by 2-3C. That would reduce LA smog as much as a total ban on cars and lorries, and cooler roofs could also save a fortune in electricity bills. On hot days in North America, up to 40% of all electricity can be consumed by air-conditioners, and each degree a city such as LA warms is reckoned to see the air-con turned up enough to need another 500MW - the output of a decent sized nuclear power station. Akbari estimates that widespread use of cooler rooftops could slash $1bn from electricity bills in the US alone.
And what about glare?
No problem, Akbari says: reflective materials need not be white. Lighter colours such as grey are good too. And there are other ways to increase the albedo of materials. Pigments that bounce back infrared light can raise the reflectivity of dark surfaces by 40% without any obvious change in colour. They are not as effective as white, which bounces back visible wavelengths of light too, but they are much better than conventional materials.
The Public Works Research Institute in Japan has experimented with paints with such pigments applied to conventional asphalt surfaces. They made a road that reflects 86% of infrared light, which helps keep the surface cool, yet reflects just 23% of visible light, to keep down glare.
(Via Jetson Green.)