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...

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