To be or not to be,that's a question.


​(选自The economist 2021年7月23日版)

A new, green air-conditioning system manages without nasty gases


And has few moving parts at its core


In a warming world it helps to stay cool. But doing so also threatens the planet. Most air conditioners use refrigerant gases called hydrofluorocarbons (HFCS). Though these do not deplete Earth’s ozone layer in the way the chlorofluorocarbons they replaced back in the mid-1990s did, they are hundreds of times more effective at trapping heat in the atmosphere than carbon dioxide is. Less-potent greenhouse gases are now being phased in as refrigerants, but these are not without problems of their own. They can be expensive, and some are inflammable.


Researchers have long sought ways to produce cooling systems that do without these troublesome gases, but none has come close to being a direct replacement. A small Irish company, however, now claims to have come up with an answer. Exergyn, based in Dublin, has developed a new type of air conditioning which not only avoids HFCS, but also has the benefit of having few moving parts at its core.

长期以来,研究人员一直寻找方 法生产没有这些麻烦的气体的冷却系统,但没有一个接近于直接替换品。但是,一家爱尔兰小公司现在声称已经找到了答案。总部位于都柏林的Exergyn公司已经开发出一种新型的空调,不仅避开了氢氟碳化物,而且其核心部分没有什么活动件。

Exergyn has been working secretly on the project for two years, in collaboration with a multinational company which it is not at liberty to name (though its partner is understood to be Carrier, a giant American manufacturer of heating and cooling equipment). The two firms are currently testing a 60kw version, which would have the capacity to cool 15-20 apartments. Exergyn has also begun talks with carmakers and aerospace companies about setting up similar joint-development projects. With cars, and some small aircraft, going electric, it is not just cooling the cabin that manufacturers are having to think about, but also cooling the batteries.


Squeeze me

Exergyn’s system uses a substance called a shape-memory alloy. smas, as they are known for short, are a group of materials with the unusual ability to return to a predetermined shape when heated. They are sometimes employed to make spectacle frames, and also in medical implants such as stents. Nitinol, the sma chosen by Exergyn, is a blend of nickel and titanium.


Exergyn的系统用的是“形状记忆合金”,一组材料,加热时具有恢复到预定形状的不寻常能力。它们偶尔被用来制造眼镜框,也被用于像支架的医用植入物。Exergyn公司选择的 “形状记忆合金”是镍和钛的混合物。

All smas release heat when deformed by compression, and then absorb it when the pressure is released and they return to their original shape. But Exergyn’s version of nitinol displays this property to a remarkable degree. For its prototype, the company produced 4cm-square plates of the alloy, each pierced by holes intended to permit the passage of a heat-carrying liquid or gaseous medium. A range of benign substances can be employed in that role. The firm’s engineers have tested water, brine, glycol and air, all with success.


To build a refrigerator involves assembling these plates into stacks of 50 or more. Four stacks make a unit. The stacks are compressed in turn by hydraulic rams or electric actuators, in a sequence that works a bit like a four-stroke engine, explains Kevin O’Toole, Exergyn’s managing director. At any given moment, one stack is being compressed, one released, one preheated and one pre-cooled.


To cool a room involves passing two circuits of the heat-carrying fluid through this four-stack unit. Fluid in a “cold” circuit first travels through a heat exchanger in the room to be cooled down, absorbing warmth as it does so (see diagram). It is then directed by a series of valves and pumps into whichever core is undergoing its relaxation stroke. The relaxing nitinol absorbs the heat burden and the fluid is pumped back to the heat exchanger for the cycle to be repeated.

要冷却一个房间,需要将两个回路的载热流体通过这个四堆叠装置。"冷"回路中的流体首先穿过 房间的热交换器得到冷却,在此过程中吸收热量(见图)。然后,再被一系列的阀门和泵导向正在进行放松冲程的任意一个核心。放松的镍钛合金吸收了热量,液体被泵送回热交换器,循环往复。


Heat thus accumulated is removed by the passage through the stack of fluid from the second, “hot”, circuit during the compression stroke. It is then dumped to the outside world via an external cooling unit. Using four stacks permits both the hot and the cold circuits to run continuously.


Tony Ennis, Exergyn’s chairman, reckons this method of cooling is not only more environmentally friendly than an hfc set-up, but will also be less expensive to buy and 30-40% cheaper to run. It will be lighter and smaller, too—an important requirement, not least because air-conditioning units often have to go up lift shafts to be installed. As for reliability, he says the prototype’s performance suggests the unit at its core could operate for more than 40 years without a problem.

Exergyn的董事长Tony Ennis认为,这种冷却方法不仅比氢氟碳化物装置更环保,而且购买成本更低,运行成本也会降低30-40%。它还将更轻更小,这也是一个重要的需求,尤其是因为空调设备经常需要上电梯井中去Exergyn的主席Tony Ennis认为,这种冷却方法不仅比氢氟碳化物装置更环保,而且购买成本更低,运行成本也会降低30-40%。它还将更轻更小,这也是一个重要的要求,尤其是因为空调设备经常需要上电梯井中安装。至于可靠性,他说,原型的性能表明,该设备的核心部分可以运行40年以上而不出现问题。

When Dr O’Toole, an expert in memory materials, co-founded Exergyn in 2012, his intention was to use nitinol to create a system that would generate electricity from low-grade waste heat. But the challenges presented by hfcs persuaded him that air conditioning would be a quicker way to bring the technology to market. Development is still continuing, but products may be only a few years away.

K.O博士, 记忆材料方面专家,2012年合创Exergyn公司时,他的意图是利用镍钛合金创建一个可以利用低级废热发电的系统。但氢氟化物带来的挑战说服了他,空调将是将该技术推向市场的更快方式。开发工作仍在继续,但产品可能只需要几年时间。

His thoughts of a generator have not diminished, though. Nor has interest in other products that could use the technology. These include refrigerators, and also heat pumps to extract warmth from the ground for domestic heating. When time allows, Dr O’Toole and his colleagues hope to get to work on those ideas, too.

不过,他对发电系统的念头并没有减少。对其他可以使用该技术的产品也没有兴趣。这其中包括冰箱和 从地下提取温气用于家庭供暖的热泵。时间允许的话,K.O和他的同事们也希望能在这些想法上下功夫。

This article appeared in the Science & technology section of the print edition under the headline "Cool ideas"


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