How does an air conditioner actually work? - Anna Rothschild

譯者: Lilian Chiu 審譯者: 麗玲 辛

Typically, with any piece of technology, you get out what you put in.

通常，對任何技術而言， 輸入什麼就會得到什麼。

Pump one unit of energy into an electric toaster

將一單位的能量 輸入到電烤麵包機中，

and you get about one out in the form of heat.

就會得到大約一單位的熱能輸出。

That’s just the first law of thermodynamics:

那是熱力學的第一定律：

energy has to be conserved.

能量一定會守衡。

But there's a piece of technology called a heat pump,

但是有一種技術，叫做熱泵，

where for every bit of energy you put in, you get 3 to 5 times as much heat out.

它輸出的熱能是 輸入能量的三到五倍。

What wizardry is this?

這是什麼巫術？

Heat pumps have been hailed as a climate-friendly heating solution

熱泵被譽為是比傳統暖氣機 更環保的解決方案，

to traditional heaters,

most of which operate by burning fossil fuels.

傳統暖氣機多半要靠 燃燒化石燃料來運作。

So much so that in 2021,

這甚至導致在 2021 年，

heating buildings was responsible for about 10%

全球與能源相關的二氧化碳排放中 有 10% 來自建築物暖氣供應。

of global energy-related CO2 emissions.

Heat pumps reduce emissions in two ways—

熱泵在兩方面可以減少排放。

first, they run on electricity,

第一，它們靠電力運作，

meaning less fossil fuel use as grids make the switch to renewable energy.

這表示將電力網換成可再生能源， 因而減少化石燃料的使用。

And second, they're more efficient than their counterparts,

第二，它們比同類產品更高效，

using less energy to produce the same amount of heat.

用較少的能源就能 產出相同量的熱能。

Where a typical oil or gas boiler is, at best, about 90% efficient,

一般的燃油或天然氣鍋爐 在最好的情況下效率約為 90%，

some heat pumps can achieve 500% efficiency.

有些熱泵的效率 可以達到 500%。

Heat pumps rely on the same technology as air conditioners.

熱泵採用的技術與空調設備相同。

And in fact, they often double as air conditioners,

事實上，它們通常也可以作為空調，

heating your home in the winter and cooling it in the summer.

在冬天讓房間變暖， 在夏天讓房間冷卻。

How? Air conditioners take heat from your home and move it outside.

怎麼做？冷氣機能把 家中的熱能移到室外。

To do so, they harness the second law of thermodynamics.

它們利用熱力學的 第二定律來做到這點。

That’s the one that says that heat will always move from a hotter object

該定律為：熱能一定會 從較熱的物體移至較冷的物體。

to a colder one.

When you turn on your A/C,

打開冷氣機時，

a fan blows the hot air from your home over coils

風扇會把家中的熱空氣吹過盤管，

containing a substance called a refrigerant.

盤管內有一種物質，稱為冷媒，

A refrigerant’s molecules turn to gas at relatively low temperatures,

相對之下，不用太高的溫度， 冷媒就會變成氣體，

so as it collects thermal energy from the hot air in your home, it boils.

因此，當它從家中的 熱空氣收集到熱能時，

它會沸騰。

Then, it passes into a compressor,

接著，它會通過壓縮機，

which pushes the gas molecules closer together,

壓縮機將氣體分子 壓縮到更靠近彼此，

heating them up even more.

讓它們變得更熱。

Now that gas is hot— way hotter than the outside air.

現在氣體是熱的了—— 比屋外空氣更熱許多。

So when a fan blows over the refrigerant,

因此，當風扇將空氣吹過冷媒時，

thermal energy transfers to the comparatively cold air outside.

熱能會傳送至屋外相對較冷的空氣。

As the refrigerant releases heat, it starts to liquefy.

當冷媒釋放熱能時，它會開始液化。

It goes through an expansion valve, which decreases the pressure,

它會通過能減低壓力的膨脹閥，

causing it to get even colder.

它就會變得更冷。

Now, it’s ready to pick up more heat from your house and start the cycle again.

如此，它就能從屋內帶走更多熱能， 再次執行這個循環。

In winter, heat pumps work exactly the same way.

在冬天，熱泵的運作方式完全相同。

But this time they pick up heat from outside and move it into your home.

但這時候，它們是把 屋外的熱能移至屋內。

Of course, it’s sometimes freezing outside when you want to use your heater.

當然，當你想用暖氣時， 戶外有時是冷到爆。

But the air doesn’t need to be warm—

但並不需要暖空氣——

it just needs to be warmer than the refrigerant to transfer its heat.

空氣只要比冷媒更暖一點， 就可以傳送熱能。

All this sounds great, but for now there are some drawbacks to this technology.

這一切聽起來很棒， 但目前這項技術仍有一些缺點。

First, refrigerants can be potent greenhouse gases.

第一，冷媒可能是強效的溫室氣體。

Hydrofluorocarbons are some of the most popular refrigerants.

最常用的冷媒包括氫氟碳化合物。

But a single hydrofluorocarbon molecule can have 2,000 times

但單一個氟氫碳分子

對全球暖化的衝擊 可達二氧化碳的兩千倍。

the global warming impact of CO2.

While in use, the refrigerant stays contained in a closed loop.

使用時，冷媒會被封在閉合的迴路中。

But when heat pumps, A/Cs, and refrigerators are improperly installed

但是當熱泵、空調， 和冰箱安裝不當時，

or thrown into landfills, the refrigerant can leak out.

或被丟棄到掩埋場時， 冷媒就可能會外漏。

So scientists are trying to create new refrigerants

因此科學家正在嘗試製造 對環境更友善的冷媒。

that are better for the environment.

Also, the colder it is outside,

此外，室外越冷，

the less efficient an air-to-air heat pump will be.

空氣對空氣的熱泵效率就會越差。

Nevertheless, over half the buildings in icy Norway use heat pumps.

然而，在冰冷的挪威， 超過一半的建築都有用熱泵。

Some people there have opted for pumps that draw heat from under the ground,

那裡有些人選擇使用 從地下抽取熱能的熱泵，

which stays more consistently warm, rather than heat from the air.

相對於來自空氣的熱能， 地下能維持更穩定的溫暖溫度。

Finally, there's the cost.

最後一點是成本。

In the US, installing a small heat pump usually costs several thousand dollars,

在美國，安裝一個小型熱泵

通常要花費數千美金，

though some people need more powerful systems,

不過有些人需要更強大的系統，

depending on the size of their home or the temperature in winter.

取決於家的大小或冬天的溫度。

Often they’re only a little more expensive than installing a new A/C system,

通常，安裝熱泵只比 安裝新的空調系統貴一點，

and the heat pump can save money on utilities in the long run.

且長遠來看，熱泵可以節省水電費。

But replacing a working system requires an upfront investment

但是，更換運作中的系統， 需要預先投資，

that a lot of people just don’t have.

很多人負擔不起。

Still, as the risks of climate change loom,

不過，隨著氣候變遷的 風險漸漸浮現，

many countries are offering subsidies to help with the costs.

許多國家都提供補助， 幫忙支付部分成本。

And some cities are creatively harnessing seas, sewage, and data centers

有些城市發揮創意，利用海洋、

排水系統，和資料中心來當作熱源，

as heat sources, using heat pumps in manufacturing,

在製造業中使用熱泵，

and even creating giant heat pumps for entire districts.

甚至為整個地區建造巨型熱泵。

So, are heat pumps actually breaking the first law of thermodynamics?

那麼，熱泵真的有打破 熱力學的第一定律嗎？

Of course not.

當然沒有。它們只是 沒有用電力來製造熱能。

They’re just not using their electricity to make heat.

They're using it to power the compressor and spin the fans.

電力是用來讓壓縮機運作， 並轉動風扇。

They get the extra energy for free— from heat in the air or underground.

熱泵能免費取得額外的能量——

來自空氣或地底的熱能。

Which is how, by putting in 1 unit of energy,

這就是為什麼輸入一單位的能量

you get 3 to 5 units of heat out.

就能輸出三到五單位的熱能。

Seems like magic, but it's just physics.

看似魔法，但不過就是物理學。