### "From CFCs to CO₂ - The Refrigerant Revolution Paves the Way to Decarbonization"

### "From CFCs to CO₂ - The Refrigerant Revolution Paves the Way to Decarbonization"

In the early 1990s, Japan was forced to work toward the total elimination of chlorofluorocarbons (CFC and HCFC) following the entry into force of the Montreal Protocol. CFCs were widely used in refrigerators, air conditioners, and other appliances, but their depletion of the ozone layer and extremely high greenhouse effect were seen as problematic. Against this backdrop, articles in 1994 were beginning to focus on the conversion to refrigeration systems using natural refrigerants - namely ammonia and carbon dioxide (CO₂) - as an environmental technology for the next generation.

Ammonia, in particular, is a refrigerant that has been used for a long time and boasts high cooling efficiency, but has a toxicity problem. On the other hand, CO₂, although known as a greenhouse gas, had an extremely low global warming potential (GWP) of "1" when used as a refrigerant, making it an ideal candidate to replace CFCs. At the time, CO₂ was still in the experimental stage, but it was already being put to practical use in Germany and Scandinavian countries, and in Japan, joint development by research institutes and companies was gaining momentum.

Thirty years later, in 2025, CO₂ refrigerants are firmly established as a core technology for a decarbonized society. CO₂-based refrigerant equipment has spread one after another, from refrigeration equipment in household refrigerators and convenience stores to vending machines and water heaters (Eco-Cute). As a result of overcoming numerous technical challenges, such as designing components that can withstand high pressure, optimizing heat exchange efficiency, and taking measures against corrosion, these systems are being used worldwide as highly energy-efficient systems.

This shift in refrigerant technology was not a mere replacement of equipment, but a fundamental change in the "cooling philosophy" of society as a whole. The 1994 article documents the "beginning" of the change, and from today's perspective, shows how visionary that step was. The spread of natural refrigerants was a "quiet revolution" in the age of decarbonization, and the trend certainly continues today.