Fighting global warming with nanotechnology
Can you imagine homes and buildings remaining cool with air conditioning, or cars that don’t heat up like ovens in open parking lots?
Stanford scholars have just come up with a new form of cooling panel that reflects sunlight back into space, thus keeping man-made structures cool even in the daytime.
The device, described in a paper published March 5 in Nano Letters, works two ways. As a broadband mirror, it reflects as much sunlight hitting a surface as possible. As a thermal emitter, it radiates the heat within a crucial wavelength range so that it escapes the Earth’s atmosphere and goes back into space rather than getting trapped as greenhouse gases that aggravate global climate change.
Prior to the experiment, engineers had been stymied by the challenge of daytime radiative cooling.
The Stanford team surmounted the challenge by utilizing nanostructured photonic materials —artificial electromagnetic media with unusual and useful functionalities resulting from structuring on a sub-wavelength scale— which can be engineered to either suppress or enhance light reflection.
The materials are composed of a combination of weak light-absorbing quartz and silicon carbide.
Practical applications of nanotech
The standard 10%-efficient solar panels currently used on rooftops to feed electricity to airconditioning systems could soon be replaced by these new cooling panels, which generate over 100 watts per square meter.
Put differently, a one-family house with 10% of roof covered by the new devices could shave 35% off its total airconditioning demand during the hottest summers.
Moreover, radiative cooling is a passive technology, needing no energy to drive moving parts, so the device can be installed and used immediately.
Implications for the world’s populations
Shanhui Fan, Stanford professor of electrical engineering and senior author of the paper, is more excited by the social than the potential commercial impact of the device.
Large numbers of the human population live in sun-scorched regions of the Earth where energy demand to fuel airconditioning presents economic and environmental challenges. Most of these people are poor, while the energy to drive cooling is usually sourced from fossil fuels, the burning of which compounds the greenhouse gas problem.
Radiative cooling can take the searing heat of the sun, and send it back into the chilly vacuum of space. — TJD, GMA News
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