Electricity can be made from the sun, the wind or the atom rather than by burning fossil fuels. Cars, buses and perhaps even lorries can be powered by batteries rather than petrol or diesel. But other parts of the economy are trickier to decarbonise. One such awkward chunk is the heating, in homes and business, of air and water. In the eu, where much of this is done by burning oil or natural gas, commercial and residential heating accounts for about 12% of the bloc’s greenhouse-gas emissions (see chart).

电力可以来源于太阳能、风能、原子能，不必燃烧化石燃料。汽车、公交车、甚至卡车都可以用蓄电池来驱动，不必使用汽油或柴油。但在其他经济领域，脱碳较为困难，其中一个棘手的领域是家庭和企业的蒸汽和热水供暖。在欧盟，大部分供暖来自石油或天然气的燃烧，商业和住宅供暖约占欧盟温室气体排放量的12%。

In principle there is a solution, in the form of heat pumps. These work like a refrigerator in reverse, gathering heat from the outside, concentrating it, and piping it into a building. The eu hopes to replace a third of the 68m gas and 18m oil boilers in residential buildings with heat pumps by 2030. That could mean a 28% fall in the total residential emissions generated by oil and gas—and that number should rise as more of the electricity powering those pumps comes from low-carbon sources.

理论上，热泵可以解决这个问题。热泵的工作原理与冰箱相反，从外部收集热量，集中起来后输送到建筑物中。欧盟希望到2030年用热泵取代住宅楼内 6800 万台燃气锅炉和1800万台燃油锅炉中的三分之一。这可能意味着石油和天然气产生的住宅碳排放总量将下降28%——随着驱动热泵的电力越来越多地来自低碳能源，这一数字会继续上升。

But there are problems with ambitious targets. Compared with boilers, heat pumps are expensive, often costing twice or three times as much as a fossil-fired boiler. Another is that, since they pump cooler water to radiators, they work best in new, well-insulated buildings. Around 60% of Europe’s housing stock is estimated to fall short of the required standards, and will need extensive—and expensive—renovation work to make them suitable.

然而，远大的目标也存在问题。热泵的价格比锅炉更贵，通常是化石燃料锅炉的两三倍。另一个问题是，由于热泵将低温水输送到散热器中，所以在隔热良好的新建筑中效果最佳。据估计，欧洲大约 60%的住宅达不到规定的标准，需要进行大规模且昂贵的翻修才能符合要求。

And there is another drawback, too. Although heat pumps powered by low-carbon electricity are undoubtedly better, from an environmental point of view, than fossil-fuelled boilers, their credentials are not entirely green. Most residential models contain environmentally damaging gases which European legislators are poised to outlaw. Redesigning the machines to work without them could mean delays in installing them.

热泵还有一个缺点。尽管从环境角度来看，低碳电力热泵固然比化石燃料锅炉更好，但其特性并非完全环保。大多数民用热泵都含有危害环境的气体，欧洲议员准备取缔它们。重新设计不含这些气体的热泵可能意味着推迟安装。

In some places, the politics of heat pumps have become bad-tempered. A German law had planned to forbid the installation of new gas-fired boilers in homes from next year. A backlash from cross voters sparked a row in the country’s coalition government before the rules were scrapped in June. On September 8th, after we published this article, German lawmakers were expected to pass a watered-down version of the rules.

在某些地方，热泵政治已经变得暴躁。德国一项法律计划从明年开始禁止住宅安装新的燃气锅炉。交叉选民的强烈反对在德国联合政府内引发了一场争论，直到6月份废除了这项法律。9月 8日，在我们发表这篇文章后，德国议员有望通过一项弱化版的法律。

Warming up

加热
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A heat pump works by warming a refrigerant in a network of pipes using the ambient heat present in the air, or from an array of pipes that are buried in the ground or under water. This turns the refrigerant from a liquid into a gas. The gas is then compressed, which raises its temperature. The resulting hot gas is pumped through a heat exchanger, where it warms the water or air that is used to heat the building. As the gas cools it returns to its liquid state, ready to repeat the process.

热泵的工作原理是利用空气中、地下管道、地下水管道中的环境热能来加热管网中的制冷剂，使制冷剂由液体变成气体，气体被压缩后升温，产生的热气被输送到换热器中，加热水或空气用于建筑物供暖。热气冷却后恢复液态，准备重复这个过程。

Because heat pumps merely move existing heat around, rather than generating it themselves, they can be extremely efficient. Some models boast efficiencies of 400% or more, which means that four kilowatts of heat can be piped into a house for every one kilowatt of electricity consumed by the pump. Modern gas boilers, which generate heat from combustion, can reach about 90% efficiency, and are prevented by the laws of physics from exceeding 100%.

由于热泵只是传递已有的热能，其本身不产生热能，因此效率非常高。有些热泵的效率高达400%以上，这意味着热泵每消耗一千瓦的电力，可以向房屋输送四千瓦的热能。现代燃气锅炉通过燃烧产生热能，效率可达90%左右，由于受到物理规律的限制而无法超过100%。
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A heat pump’s efficiency is lower in winter, when there is less heat to be gathered from the air, although they work at temperatures as low as -25°C. But heat pumps tend to produce water heated to around 55°C. This is lower than most gas boilers, which might manage 75°C or so. That means that fitting heat pumps to older buildings often needs extra insulation, bigger radiators or even underfloor heating, all of which is disruptive and pricey.

热泵在冬季效率下降，因为从空气中收集的热能变少，不过工作温度可低至-25℃。但热泵产生的热水一般在55°C 左右，低于大多数燃气锅炉的75°C 左右。这意味着在旧房屋中安装热泵通常需要增添隔热材料、更大的散热器、甚至地暖，这些都具有破坏性，而且费用很高。

Most modern heat pumps use hydrofluorocarbons (hfcs) as their refrigerants. These transform from liquid to gas at the right sort of temperature, and can carry a good deal of heat. But hfcs are also potent greenhouse gases, with climate-changing power that can be several thousand times higher than carbon dioxide, the main man-made greenhouse gas. Leaks of hfcs from heat pumps and other equipment, such as certain types of refrigeration and air-conditioning systems, account for around 2.5% of the eu’s total greenhouse-gas emissions—not far off the amount caused by air travel in the region.

大多数现代热泵使用氢氟碳化物作为制冷剂，它在适当的温度下由液体变为气体，并且可以携带大量的热能。然而，氢氟碳化物也是强效的温室气体，它对气候的影响可能比主要的人为温室气体二氧化碳高出数千倍。热泵及其他设备（例如某些类型的制冷和空调系统）泄漏的氢氟碳化物约占欧盟温室气体排放总量的 2.5%，与欧盟航空旅行的排放量差不多。

Propane, and propane accessories

丙烷及其配件

With that in mind, the eu had planned this summer to put the finishing touches to new rules that would have required hfcs to be replaced with cleaner alternatives by 2027. But discussions have broken down. One side, backed by Germany and the Netherlands, is keen to get on with the phase-out. The other, supported by a number of eastern European countries and some heat-pump manufacturers, wants the deadline moved into the 2030s.

考虑到这一点，欧盟原计划今年夏天对新规定进行最后的修订，要求到2027年用清洁的制冷剂取代氢氟碳化物。但讨论已经破裂，一方在德国和荷兰的支持下热衷于继续淘汰进程。另一个方在许多东欧国家和热泵制造商的支持下，希望将最后期限推迟到本世纪30年代。
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Other refrigerants exist. The chemical industry has developed a class of chemicals called hydrofluoroolefins (hfos). These are less powerful greenhouse gases than hfcs, although still more potent than carbon dioxide. But some countries, including Denmark, Germany, the Netherlands, Norway and Sweden, want to restrict hfos, too, because studies show they could pollute rainwater. Many heat-pump manufacturers are therefore turning to so-called natural refrigerants, which have the lowest global warming potentials of all. Some of these were employed in refrigeration long before synthetic substances were developed. They include ammonia and even carbon dioxide itself. But the front-runner to replace hfcs in residential heat pumps is propane.

还有其他制冷剂。化工行业研发出一种名为氢氟烯烃的化学品。它的温室气体效应低于氢氟碳化物，但仍高于二氧化碳。但是，丹麦、德国、荷兰、挪威、瑞典等国家也希望限制氢氟烯烃，因为研究表明它可能会污染雨水。因此，许多热泵制造商着眼于所谓的天然制冷剂，其温室气体效应是最低的。某些天然制冷剂早在合成物质问世之前就已用于制冷，包括氨，甚至二氧化碳。然而，丙烷在民用热泵中取代氢氟碳化物方面遥遥领先。

The global-warming effect of propane is only a little stronger than that of carbon dioxide. The problem with using it in a heat pump is that, unlike hfcs, it is flammable. It is also odourless, which is why when propane is used as a fuel it is given a “rotten egg” smell so that it can be easily detected if it leaks. That is not possible in a heat pump, since the chemicals that produce the smell interfere with the refrigeration process.

丙烷的全球变暖效应仅比二氧化碳强一点点。不同于氢氟碳化物，热泵使用丙烷存在易燃问题，而且无味，这就是为什么燃料用途的丙烷会被添加一种“臭鸡蛋”的气味，以便在泄漏时容易被发现。这在热泵中行不通，因为产生臭鸡蛋气味的化学物质会干扰制冷过程。
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For that reason, extra rules apply to propane-powered pumps. If propane is pumped inside a building, as in “split systems” which mount the heat-exchanging equipment indoors, then the volume of gas in the system is limited to 150 grams, about a fifth of the amount of refrigerant typically used in an hfc model. If more gas is used, extra safety features, such as leak sensors and automatic venting systems, have to be fitted. This raises the cost still higher, and makes installation even more fiddly—especially in the older buildings less well-suited to the technology.

因此，针对丙烷热泵出台了额外规定。以换热器安装在室内的“分体式热泵”为例，如果将丙烷输送到建筑物内，那么热泵中的丙烷填充量被限制在150克，约为氢氟碳化物热泵的制冷剂常用量的五分之一。如果使用更多的丙烷，就必须安装额外的安全装置，例如泄漏传感器、自动通风设备等。这会使成本更高，安装也更加繁琐，尤其是在不太适合该技术的旧房屋中。

According to the European Heat Pump Association (although not all its members seem to agree), the rapid phasing out of hfcs would “slam on the brakes for heat pump deployment”. It argues that a laxer schedule would give the industry more time to develop propane-based systems that could be installed more easily in a greater variety of homes.

根据欧洲热泵协会的说法（但并非所有成员都同意），快速淘汰氢氟碳化物“会给热泵的部署踩下急刹车”。该协会认为，放宽时间表能给业界更多时间来研发丙烷热泵，使其更易于安装在更多类型的住宅中。

Delaying things is unnecessary, according to a paper presented to European legislators by a group of more than 40 scientists. They point out that it took the refrigerator industry between three and five years to switch to cleaner gases, like isobutane, in the 1990s. (Chlorofluorocarbons, that industry’s refrigerants of choice, were phased out in that decade because of the damage they do to the ozone layer.) What heat-pump makers have failed to do, the paper argues, is to reduce the amount of refrigerants which heat pumps contain because this was not considered to be important with non-flammable hfcs.

根据一份由40多名科学家组成的小组提交给欧洲议员的论文，推迟时间表是没有必要的。他们指出20世纪90年代，冰箱行业只用了3-5年就改用了异丁烷等清洁气体（该行业首选的制冷剂氯氟烃在90年代被逐步淘汰，因为它对臭氧层造成破坏）。该论文指出，热泵制造商未能做到减少热泵制冷剂的用量，因为他们认为这一点对于不易燃的氢氟碳化物来说并不重要。

Despite what their trade body says, a number of producers, including Viessman and Robert Bosch, two German firms, along with Mitsubishi Electric, a Japanese one, have already launched propane-filled heat-pumps. They tend to be large “monoblock” systems that are mounted outdoors, where any escaping gas can disperse quickly and harmlessly into the air. Viessman says that, besides its eco-friendly credentials, propane also makes it easier to produce heat pumps that can supply water at 70°C—the sorts of temperatures that gas boilers produce. That could remove the need to replace radiators or install underfloor heating in many cases, saving a considerable amount of money.

不管他们的行业组织怎么说，许多生产商已经推出了丙烷热泵，包括两家德国公司菲斯曼和罗伯特博世、以及日本三菱电机。丙烷热泵通常是安装在室外的大型“一体式”设备，泄漏的甲烷气体可以快速无害地扩散到空气中。菲斯曼公司表示，丙烷不仅有环保特性，还能使我们更轻松地制造出提供70°C热水的热泵——相当于燃气锅炉提供的热水温度。在许多情况下，这可以免于更换散热器或安装地暖，从而节省大量资金。

Many properties, and especially flats, may lack enough outside space for a monoblock. Firms are therefore working on split systems that can get by on modest quantities of propane. They are being helped by Lena Schnabel and her colleagues at the Fraunhofer Institute for Solar Energy Systems in Freiburg, Germany. Dr Schnabel’s group have tested a number of designs, including one that can make do with just 146 grams of propane. That was achieved by redesigning and optimising most of the pump’s important components, such as the compressor, heat-exchanger and pipework, and the use of prototype parts.

许多住宅，尤其是公寓，可能缺乏足够的外部空间来安装一体式热泵。因此，各家公司正在研发只需使用少量丙烷的分体式热泵。他们得到了德国弗莱堡弗劳恩霍夫太阳能设备研究所的莉娜·施纳贝尔和她同事的帮助。施纳贝尔博士的团队已经测试了多个设计方案，其中有一种热泵只需填充146 克丙烷。这是通过重新设计和优化热泵的大部分重要零部件来实现的，例如压缩机、换热器、管道、使用原型零部件等。

Dr Schnabel is optimistic that new designs containing a small charge of propane will, in the next few years, mean it is possible to directly replace a gas boiler inside a flat with a heat pump that will be safe, eco-friendly and produce similar temperatures. The heat source could be a communal one, on the roof of a building or buried in a basement, powering dozens of individual indoor units. There is even talk of raising the 150-gram limit, though, says Dr Schnabel, “for safety it really makes sense to use as little refrigerant as possible”.

施纳贝尔博士乐观地预测，新设计只使用少量的丙烷，这意味着在未来几年内，可以使用安全、环保、产生相似温度的热泵直接取代公寓里的燃气锅炉。热泵可以使用位于屋顶上或铺设在地下室的公共热源，为数十台室内设备供暖。施纳贝尔博士说，尽管有人讨论提高150克上限，“但为了安全起见，尽可能少地使用制冷剂确实是有道理的”。

If such devices can be perfected, then many of the downsides of heat pumps could be eliminated. Not only would they become greener machines in their own right, they would become easier and cheaper to fit in old properties, too. And that would help take some of the heat out of the arguments that surround them.

如果这种设备得到完善，就可以消除热泵的许多缺点。不仅设备本身变得更环保，而且更易于安装在旧房屋中，安装费用更便宜，这将有助于平息有关热泵的争论。

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