These new solid-state ACs promise a cool future. Scientists aren’t so sure.

这些新型固态空调承诺带来凉爽的未来，但科学家们对此并不确定。

After three years of record-breaking heat, this one is set to be yet another scorcher. Air-conditioning? Not going anywhere. The International Energy Agency projects that the number of AC units will triple by 2050. That’s good for health—one Lancet study estimated that AC prevented nearly 200,000 premature deaths in 2019 alone—but bad for the planet. Artificial chill already accounts for 7% of global electricity use and 3% of greenhouse-gas emissions, and if improperly disposed of, the units can leak refrigerants with more global-warming potential than carbon dioxide.

在经历了三年破纪录的高温之后，今年注定又是一个酷暑。空调会消失吗？当然不会。国际能源署预计，到2050年，全球空调数量将增加两倍。这对健康有益——《柳叶刀》的一项研究估计，仅在2019年，空调就预防了近20万例过早死亡——但对地球却不利。人工制冷目前已占全球电力消耗的7%和温室气体排放的3%，如果处置不当，空调设备还会泄漏全球变暖潜势远高于二氧化碳的制冷剂。

Feeling the heat, a number of scientists and startups are hoping to amp up solid-state cooling, which is currently used at a small scale for things like mini fridges, EV batteries, and some high-end gaming computers. Traditional ACs transfer heat by using a compressor and a fan to circulate a refrigerant and turn it from liquid to gas. Solid-state systems, on the other hand, move heat through conductive materials like gadolinium and bismuth telluride—which could theoretically cool spaces and surfaces with fewer messy side effects.

面对高温压力，许多科学家和初创公司希望大力发展固态制冷技术。目前，该技术仅在小型设备中应用，如迷你冰箱、电动汽车电池和一些高端游戏电脑。传统空调通过压缩机和风扇循环制冷剂，使其在液体和气体之间转换来传递热量。相比之下，固态系统通过钆（gadolinium）和碲化铋（bismuth telluride）等导电材料来移动热量，理论上可以在减少负面影响的情况下冷却空间和表面。

The catch is whether they can match the efficiency of conventional AC. “One of the key questions that remain is why are the solid-state coolers not as efficient as typical thermodynamic cycles?” says Pramod Reddy, a professor of mechanical engineering at the University of Michigan who studies heat transfer. Research and pilot programs are underway to test a range of approaches.

问题的关键在于它们能否达到传统空调的能效水平。密歇根大学研究传热学的机械工程教授Pramod Reddy表示：“目前遗留的关键问题之一是，为什么固态冷却器的效率不如典型的热力学循环？”目前，各项研究和试点项目正在测试多种技术路径。

Brooklyn-based Mimic Systems uses thermoelectric cooling, which passes a current through semiconductive materials to shift heat from one side to another. Its room-scale climate control system is being piloted in an apartment in Vancouver. The German company Magnotherm is set to test its system, which relies on a magnetocaloric setup that transfers heat by magnetizing and demagnetizing materials, in a chain of supermarkets. A team in Hong Kong has announced that its elastocaloric device, whose material heats and cools as it expands and contracts, can dip below 0 °C. And the UK’s Barocal is betting on barocaloric systems, which change temperature in response to shifts in pressure.

总部位于布鲁克林的Mimic Systems公司采用热电制冷技术，通过电流流经半导体材料将热量从一侧转移到另一侧。其房间级气候控制系统正在温哥华的一间公寓中进行试点。德国公司Magnotherm准备在一家连锁超市测试其系统，该系统依赖磁热装置，通过材料的磁化和去磁来传递热量。香港的一个团队宣布，其弹热制冷装置（材料在膨胀和收缩时会加热和冷却）可以将温度降至0°C以下。英国的Barocal公司则押注于压热制冷系统，该系统通过压力变化来改变温度。

But experts, especially in thermoelectrics, have doubts about how well any solid-state scheme can compete. For most modern HVAC systems, the coefficient of performance (COP) is 3, explains Jeff Snyder, a professor at Northwestern University who studies electrical and thermal conductivity. That essentially means the system moves three units of heat for every unit of energy that goes into it. Thermoelectrics in particular tend to have a much lower performance at high levels of temperature change, Snyder says, which means they’re best suited for niche uses such as cooling the back of a car seat.

但专家们，尤其是热电领域的专家，对任何固态方案的竞争力都持怀疑态度。西北大学研究电导率和热导率的教授Jeff Snyder解释说，对于大多数现代暖通空调（HVAC）系统，其性能系数（COP）为3。这意味着系统每消耗一个单位的能量，就能移动三个单位的热量。Snyder指出，热电制冷在温差较大时性能往往会大幅下降，这意味着它们最适合用于汽车座椅靠背冷却等利基市场。

Efficiency, however, isn’t everything, argues Lindsay Rasmussen, a manager at the Rocky Mountain Institute’s climate tech accelerator Third Derivative, which supports both Magnotherm and Mimic. In the US, most ACs currently in use employ a refrigerant called R410A, which has a global-warming potential more than 2,000 times that of carbon dioxide. Plus, their moving parts can make them less durable, especially compared with a solid-state model that’s less mechanically complex.

然而，落基山研究所气候技术加速器Third Derivative的经理Lindsay Rasmussen认为，效率并非一切。该机构同时支持Magnotherm和Mimic。在美国，目前使用的大多数空调都采用一种名为R410A的制冷剂，其全球变暖潜势是二氧化碳的2000多倍。此外，传统空调的运动部件使其耐用性较差，尤其是与机械结构简单的固态模型相比。

Still, a dearth of units makes it hard to answer the efficiency question. To understand how well alternatives work, says Rasmussen, researchers need to compare their long-term energy consumption with that of conventional models instead of simply looking at COP. Mimic claims, for example, that its room-scale model should match the draw of a typical AC unit over the course of a year. Elastocaloric and barocaloric systems also have promise, Rasmussen adds, but room-scale prototypes are probably two to three years away.

尽管如此，由于缺乏设备，很难回答效率问题。Rasmussen表示，为了了解替代方案的效果，研究人员需要将其长期能耗与传统模型进行比较，而不是仅仅关注COP。例如，Mimic声称其房间级模型在一年内的耗电量应与典型空调相当。Rasmussen补充说，弹热和压热系统也很有前景，但房间级原型机可能还需要两到三年才能问世。

In the end, the likelihood that solid-state cooling could replace compressor-based AC is slim. But as the planet warms and places like India install tens of millions of new AC units over the next decade, supplanting even a small number could make a dent. “If [solid-state] could take over even a 5% market share,” Rasmussen says, “that is a really large potential impact.”

最终，固态制冷取代压缩机式空调的可能性很小。但随着地球变暖，以及像印度这样的国家在未来十年内安装数千万台新空调，即使能取代其中一小部分，也能产生显著影响。Rasmussen说：“如果（固态制冷）能占据哪怕5%的市场份额，那也将产生巨大的潜在影响。”