撰文/播音 Christopher Intagliata

翻译 Meatle

审校 丁可含

A thin film coating can chill a vat of water to 15 degress Fahrenheit cooler than its surroundings, by absorbing—and then emitting—the sun's infrared rays. Christopher Intagliata reports.

薄薄的一层涂层能通过 吸收-发射太阳的红外线的方式，将一缸水的温度降低15℉（约8.3℃）。

You've probably seen pictures of Greek villages, where every house is painted bright white. The paint reflects the intense sunlight of the Mediterranean. And it works pretty well to keep the houses from heating up in the sun. But it doesn't actively cool them.

或许你看过希腊村庄的照片——每间房子都被涂成白色。房子上的涂料可以反射地中海强烈的阳光，有效地限制室内温度的上升，但无法有效地降温。

To understand why, consider what the white paint does. Here's how optical scientist Xiaobo Yin of the University of Colorado describes it: "It's a mirror for the sunlight, it's also a mirror for the radiation as well." And it might seem like reflecting all those incoming rays would be a good thing. But the benefit is limited. Because what it really means, Yin says, is that the houses, well, "they don't release much energy." Release more energy, again in the form of infrared radiation, aka heat—and you effectively get free A/C.

要知道这些现象的原因，就需要了解白色涂料起到的作用。卡罗拉多大学（University of Colorado）的光学科学家Xiaobo Yin是这样分析的：“这些涂料像镜子一样反射太阳光，也反射了其他辐射。”看上去反射所有接收到的射线的效果不错，但好处有限。就像Yin说的那样，这些房子“没有释出能量。”通过放射红外线（也就是热能）释出更多的能量，就能达到空调的效果。

So Yin and his colleagues built a material that does exactly that: reflects visible light, but also emits infrared wavelengths. Which gives it the power to actually cool. It's two layers: a top layer of polymer, packed with glass beads just eight microns across—so they can absorb and then emit infrared radiation. And a silver coating on the bottom.

因此Yin和他的同事制作了能够反射可见光，也能释放出红外光的材料。这些特性使这种材料能够带来清凉。这种材料由两层组成：顶层是一层聚合物，其中填充有8微米大小的玻璃微珠，实现了吸收并发射红外线的功能；而底层则是银涂层。

The coating reflects 96 percent of solar radiation—a slight improvement on white and silver paint. But the game-changing part: it also has a cooling power of about 100 watts per square meter. Translation: enough to cool a frying-pan-sized amount of water to about 15 degrees Fahrenheit cooler than ambient temps. Even while sitting in the sun. The finding is in the journal Science. [Yao Zhai et al., Scalable-manufactured randomized glass-polymer hybrid metamaterial for day-time radiative cooling]

这种涂层能够反射96%的太阳辐射，略优于白色和银色涂料。但是，这种涂料也带来了100瓦/平方米的制冷能力，使之远优于白色和银色涂料。这种制冷能力能够使到煎饼锅大小的水量，从常温下降15℉（约8.3℃），即使这些水被放在阳光之下。该发现发表在《科学》杂志上。

That cool water example has wide applications. "This water can be used to cool a house, cool a data center, or even cool a thermoelectric power plant." That's Yin's colleague at the University of Colorado, Ronggui Yang. And he says it's a cheap way to cool things down. Just don't put the material directly on your roof. "It also cools down during the wintertime. And you do not want that to happen." No. Definitely… not cool.

用水来距离是因为冷却水有着广泛的用途。“这些水能用于住房、计算中心、甚至是火电厂。”Yin在科罗拉多大学的同事，Ronggui Yang说道。他认为这是廉价的冷却方式。但不要直接把这种物料用于屋顶。“这种物质在冬季也会有效，但你不会想那样…”是的，那是冷，不是凉快。