When it comes to keeping buildings cool in warm climates when the sun is shining, the standard solution has been mechanical air conditioners. In fact, the development of artificial cooling for buildings has enabled people to live and work in more extreme climates. Today, the amount of energy used for cooling is climbing steadily. Rather than making air conditioners more efficient to reduce energy consumption, what if there was a different way to cool a building?

Engineers at Stanford have developed a cooling panel that could cool buildings and even cars when the sun is shining. The panel incorporates nanostructured materials to reflect sunlight and effectively radiate heat back into space. It’s a simple structure with no moving parts and does not require power to operate.

The new device is capable of achieving a net cooling power in excess of 100 watts per square meter. By comparison, today’s standard 10-percent-efficient solar panels generate the about the same amount of power. That means Fan’s radiative cooling panels could theoretically be substituted on rooftops where existing solar panels feed electricity to air conditioning systems needed to cool the building. To put it a different way, a typical one-story, single-family house with just 10 percent of its roof covered by radiative cooling panels could offset 35 percent its entire air conditioning needs during the hottest hours of the summer.

When these innovators approached the issue of cooling, they set aside the notion of air conditioning as we’ve come to think of it and found a different way to deliver a benefit people need with fewer resources. Their solution will look nothing like air conditioners on the market today. What other products are ripe for a similar transformation?

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