From Snow and Ice to Refrigeration Technology
Indians, Egyptians, Greeks, Romans, and many others used to collect snow and ice and store it in natural caves to preserve food during the warmer months. In Switzerland, this practice remained common until the 19th century.
The Beginnings of Mechanical Refrigeration
Mechanical refrigeration technology was invented in the 19th century. Early pioneers such as John Gorrie, Carl von Linde, Alexander C. Twining, and Ferdinand Carré had to use natural refrigerants in their refrigeration systems, simply because there was not yet a chemical industry capable of providing synthetic refrigerants.
The Era of Safety Refrigerants
In the late 1930s, chlorofluorocarbons (CFCs) were developed as non-toxic and non-flammable so-called safety refrigerants, enabling refrigeration systems to be used safely in private homes, grocery stores, and other public buildings. Although harmless to the local environment, CFCs proved to be extremely harmful to the global environment. They depleted the ozone layer and contributed significantly to global warming, now often referred to as the climate crisis. Beginning in 1987, the Montreal Protocol brought the worldwide use of CFCs and HCFCs to an end. Hydrofluorocarbons (HFCs) and fluorocarbons (FCs) were developed in the late 1980s and early 1990s to replace CFCs and HCFCs as safety refrigerants. While they were also harmless to the local environment, they continued to contribute to the warming of our planet.
The Fourth Generation and the TFA Problem
As HFCs and FCs had to be phased out because of their global warming potential—regulated globally through the Kigali Amendment to the Montreal Protocol and implemented in Europe through the EU F-Gas Regulation—they were replaced by another family of synthetic refrigerants known as HFOs. Although this fourth generation of refrigerants remains non-toxic and only mildly flammable, it poses what may be the greatest threat to our planet. HFOs were deliberately designed to break down rapidly in the atmosphere in order to minimize their global warming potential (GWP). Unfortunately, many of them decompose into trifluoroacetic acid (TFA) once they enter the atmosphere. TFA subsequently contaminates soils and water bodies, including groundwater. Pure TFA is toxic and, even in aqueous solution, can damage the liver and the unborn fetus. Only recently has TFA been classified as a reproductive toxicant. Today, TFA is found in all Swiss lakes and in groundwater at many locations throughout Switzerland, often at concentrations exceeding those currently considered safe for drinking water. Nevertheless, it is present in drinking water at exactly these concentrations because existing water treatment technologies cannot effectively remove it from lake water or groundwater. Before the introduction of HFCs, HFOs, and fluorinated pesticides, neither our soils nor our waters contained TFA.
Natural Refrigerants as a Sustainable Alternative
Safe alternatives have existed since the 19th century. Natural refrigerants such as ammonia, carbon dioxide, hydrocarbons, water, and air are environmentally benign and help protect Mother Earth from losing her protective ozone layer, overheating her atmosphere, and contaminating her precious drinking water resources.
IKKU and the Development of Sustainable Solutions
The IKKU – Institute of Refrigeration, Air Conditioning and Environmental Engineering at Karlsruhe University of Applied Sciences (HKA) – has always focused on the safe and energy-efficient use of natural refrigerants. For applications where local safety concerns exist, IKKU has developed energy-efficient and safe ice slurry systems as secondary refrigerants and as solutions for thermal energy storage. Over its twenty years of existence, IKKU has made significant contributions to the development of environmentally friendly refrigeration, air-conditioning, and heat pump systems. The institute remains committed to advancing sustainable refrigeration, air-conditioning, and heat pump technologies in the years ahead, helping to make our planet a better place for future generations. Our joint EU project SophiA – Sustainable Off-grid Solutions for Pharmacies and Hospitals in Africa – carried out by HKA and OST together with eleven international partners, is an excellent example of such sustainable, clean, reliable, and affordable solutions. Its solar-powered refrigeration systems using propane, CO₂, and ethane demonstrate the potential of natural refrigerants for delivering essential cooling services in regions without reliable access to electricity.
World Refrigeration Day: A Time to Reflect and Look Ahead
World Refrigeration Day on 26 June is an excellent opportunity to take a short break, enjoy a cold drink with ice cubes, have an ice cream, and appreciate the achievements of mechanical refrigeration systems. Personally, I am grateful and somewhat proud to have contributed for almost forty years to the development of sustainable refrigeration, air-conditioning, and heat pump systems using natural refrigerants—the first and, in my view, the last family of refrigerants.
About the Author
Prof. Dr.-Ing. Michael Kauffeld served as Director and Spokesperson of the IKKU – Institute of Refrigeration, Air Conditioning and Environmental Engineering at Karlsruhe University of Applied Sciences from 2009 to 2025. For decades, he has conducted research and development in sustainable refrigeration, air-conditioning, and heat pump technologies using natural refrigerants and is internationally recognized as an expert in environmentally friendly refrigeration engineering.