The air stands between the blocks of New York's blocks, people groan under the humid temperatures. In that summer of 1902, the young engineer Willis Haviland Carrier invented a device that may appear to be a miracle machine that has changed the world: the modern air conditioning system. Carrier takes a radiator and lets air flow between the pipes filled with cold water. Because the warm air condenses on it, the air removes moisture. And: by the way it also cools them. The inventor reports the patent on his flash of inspiration in 1906 as a "apparatus for the treatment of air". The company "Carrier" founded by him in 1915 is now one of the world's largest manufacturers of refrigeration systems of all kinds. This is how the history of the "Father of Air Conditioning" is often told online.
But unfortunately, Carrier's invention has unpleasant, almost ironic side effects: air conditioners cool rooms, but warm the world. More than 10 percent of global electricity demand is already accounted for by air conditioning technology to cool buildings. And the trend is rising. In addition, air conditioning systems often contain refrigerants that are harmful to the environment and the climate. At the same time, the heat days are increasing globally, the need for cool retreats is increasing. Forecasts assume that from the year 2030, more energy will be needed worldwide for cooling than for heating. A real dilemma. Researchers are therefore working hard to make air conditioning technology more sustainable, environmentally friendly and efficient.
The history of air conditioning had started so promising. Their triumphal march made people more productive in summer because you can work more concentrated in cool rooms. Once inhospitable habitats in tropical and subtropical areas were suddenly opened up. Industrial metropolises such as Dubai or Singapore were created in places where it was too humid and too hot to do sweaty work for hours in closed workshops. Globalization also drove air conditioners ahead. The number of heat deaths sank, heat-sensitive products such as meat suddenly remained for longer, the entire high-tech industry from chip production to hot server rooms is only conceivable due to climate technology.
Refrigerant transports heat away
Climate systems work very similar to refrigerators. Both devices convey heat energy from one place with a lower temperature to a place with a higher temperature - contrary to the second main rate of thermodynamics. In order for this to work, a refrigerant removes heat from the interior by evaporating it in normal pressure. Then it is compressed in a compressor and very hot. The heat is available in the air outside the building and becomes liquid. Then the refrigerant flows back into the building stone. The pressure is reduced via a valve, the refrigerant extends and cools down strongly. Now it can absorb heat from the interior and evaporate again - the circulation starts again.
The fact is: according to estimates by the International Energy Agency (IEA), the energy consumption for room cooling worldwide has more than tripled since 1990. While in Europe less than ten percent of private households still have air conditioning, in the USA it is already more than 90 percent. On particularly hot days, it can happen that more than 70 percent of the peak electricity demand in residential buildings there is accounted for by cooling rooms. If the trend continues as it is at present, two thirds of all households worldwide could have air conditioning by 2050, the IEA predicts. In the Mediterranean region, the suitcase-sized, loudly buzzing outdoor modules hanging on the houses have long been part of the landscape in many places.
The Germans, on the other hand, rely on a solid construction and good insulation for decades, if not for centuries: in summer the thick masonry keeps the warm air outside, the cool air inside, and in winter. This was sufficient for our moderate latitudes. There are almost exclusively in the country in office buildings, hospitals, shopping centers and hotels. However, not only are the days hotter, the tropical nights with temperatures over 20 degrees also increase according to the German weather service. There is hardly any time to ventilate and take a deep breath.
Peter Schossig from the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg not only observes an increasing demand for air conditioning technology in German private households. "People's needs have changed," he says. "If you get into the air -conditioned car from the cool office, you don't want to sweat at home." At the moment, it is usually still enough to keep the warmth outside with shading such as roller shutters or blinds. "It doesn't make sense anyway if it is more than 10 degrees cooler inside than outside," says the physicist. However, according to the recommendations of the World Health Organization, the room temperature should not be exceeded 32 degrees during the day and even kept below 24 degrees at night to prevent heat -related diseases. So what to do if ventilation and isolation is no longer sufficient?
Heat pumps can also cool
House and apartment owners advise Peter Schossig to the heat pump. "Many do not know - but more and more of the devices can also cool," says the thermal systems and building technology expert. At least theoretically. In practice, you must also be designed for it - with a so -called four -way valve. The system releases heat in winter, in summer it absorbs warmth. However, this does not help the tenants of a poorly insulated old apartment on the attic. That also admits. "Solutions are not easy here and have to be searched for individually in consultation with the landlord."
However, from his point of view, the small mobile air conditioners from the hardware store are rarely a good alternative. "They are usually very inefficient and should not be used if possible," says Schossig. Because where cooling takes place, waste heat is generated and these monoblock systems are usually blown outside via a hose. "Often these tubes then hang out of the open window," says the researcher. "You can't prevent warm air from flowing in there at all." This almost nullifies the entire cooling effect.
So-called split systems are better. These are the boxes that are known from vacation in southern European countries: the compressor and the capacitor hang outside, the evaporator inside. The devices are connected via lines through which the refrigerant flows. However, they are significantly more complex and expensive to install - and often also energy guessers. It helps when the electricity comes from an in -house solar system.
"Maybe the landlord will let you talk to him if the heat is getting unbearably hot in the house, and is considering a conversion to a central system," says Schossig. The large facilities, as they are available in office buildings and hospitals, are usually not as bad as their reputation. "They often release the heat into the groundwater or soil via an Earth probe," says Schossig. More and more users are also relying on the equal use of heat and cold of air conditioning units, for example in hospitals. Waste heat can be used excellently for the sterilization of surgical cutlery or for heating the water in the laundry.
Calfutists are a big problem for the climate and the environment
That sounds like Willis Carrier thought up a miracle machine rather than a hell machine back then, doesn't it? Soon after he was granted his patent in 1906, Carrier set about developing his invention further. Instead of using cold water, he then used ammonia as a circulating refrigerant. But ammonia has a big disadvantage: it smells pungent and is toxic.
In the 1930s, synthetic refrigerants were increasingly established based on halogen hydrocarbons. They are non -toxic, flame -retardant and cheap to produce. However, it was quickly shown: fluoro-cheeking hydrocarbons (CFC) destroy the protective ozone layer, partially fluorated hydrocarbons (HFKW), depending on the substance, have an increased greenhouse potential compared to carbon dioxide, expressed as a GWP (global warming potential). "The refrigerants currently used are extremely climate -damaging in over 95 percent of the air conditioning systems," the Federal Environment Agency writes.
As a rule, the gases only run out in small quantities from the cooling circuits, but: "Synthetic refrigerants and outdated systems cause considerable greenhouse gas emissions-eight million tons of CO2 equivalents in 2020," said the President of the Federal Environment Agency, Dirk Messner, recently. While FCKW has been banned in the EU since 1995, the use of HFKW has only been gradually restricted since 2015.
Peter Schossig praises this so-called F-Gas Regulation of the European Commission. "The regulation is very effective, but so far this determination has been limited to the EU," he says. By gradually reducing the quantities of HFCs available on the market, their emissions are to be reduced to 35 million tonnes of CO2 equivalent by 2030. An amendment to the regulation presented in April provides for even tightening the measure.
The idea behind it: Industrial to develop - and to use alternatives. With the recent change in the Montreal protocol, an international agreement, many other countries have also committed themselves to gradually producing fewer HFKWs. "Technically, it would already be feasible to rely on natural refrigerants in many applications with a GWP from 0 to 4 instead of 4000 or more," says Schossig. In addition to ammonia, these natural alternatives also include CO2, hydrocarbons such as propane and isobutan, air and water. "However, they all have some disadvantage - they are either toxic, flammable, poorer compressed or freezing at 0 degrees."
Propane, for example, with which gas grills or camping stoves are also operated, is highly flammable. Therefore, only a maximum of 150 grams per refrigeration cycle may be used indoors without additional safety measures. This is already being implemented in refrigerators. Researchers at Fraunhofer ISE are currently developing a compact, refrigerant-reduced and cost-efficient propane refrigeration circuit for heat pumps. "We want to show that alternatives to synthetic refrigerants are efficient and safe," says Peter Schossig.
Use of propan can slow down climate heating
It is worth taking up the challenge. In a recent study from the "Proceedings of the National Academy of Sciences", researchers from the Austrian-based International Institute for Applied Systems Analysis come to the conclusion that a complete conversion to propane as a refrigerant in split air conditioning systems could prevent a warming of 0.09 degrees by the end of the century. "The use of natural refrigerants is 'future-proof'," the initiative "Refrigerants, naturally!«. "It is unlikely that new environmental regulations will prohibit or severely restrict their use.«
Natural "air conditioning systems"
A major problem, especially for the climate in cities, is the increasing sealing of areas. Around 44 percent of the residential and traffic areas in Germany are currently sealed, i.e. built-up, concreted, asphalted, paved or otherwise secured. This corresponds to an area of about 22,600 square kilometers. Almost 100 square kilometers are added per year. Because sealed surfaces absorb the solar energy rather than reflect it and cannot store water, densely built-up areas heat up even more. In order to improve the climate in residential and office buildings and reduce the need for air conditioning systems, measures can be implemented that even have a positive impact on the climate.
How important it is to develop climate -friendly cooling systems shows a look at the heat -set statistics: According to a modeling study of 2021 published in the specialist journal "The Lancet", an estimated 500,000 people in connection with extreme heat die worldwide. Children, old and pregnant women are particularly at risk. They are often not yet or no longer able to sweat sufficiently and to cool the body.
A team of experts has therefore developed a heat action plan for the city of Mannheim. Part of it is a map that lists places where people can cool off. According to a research by the weekly newspaper "Die Zeit" from this year, however, only one in five districts in Germany has such a heat protection concept so far.
In the Californian desert city of Palm Springs, heating plagues can look for refuge in »Cooling Centers« without their own air conditioning. As soon as the thermometer shows more than 38 degrees, the city provides air -conditioned public spaces in which people can cool off. In the USA, Willis Haviland Carrier is revered for his invention like a hero: "Go to your knees - immediately - and say Willis Carrier a huge thank you," the "Chicago Tribune" demanded.
However, it would be much more important than improving the climate indoors to get a grip on the climate outside. But this requires more than one hero. All of us.
