Where would humankind be without the refrigerator? Introduced in the early 20th century, the now ubiquitous appliance makes food storage convenient and safe. To accomplish this impressive feat, refrigerators rely on substances that have thermodynamic properties. Aptly named refrigerants, they change from liquids to gases and back again. At the end of the refrigeration cycle, the refrigerant is a cold liquid capable of cooling an interior space. But because many of these substances are harmful to humans and/or the environment, scientists are still searching for the perfect refrigerant. Recent advancements, however, indicate that the breakthrough is just around the corner.

A Brief Look Back

The earliest mechanical refrigeration systems used ammonia, methyl chloride, and sulfur dioxide as refrigerants. Unfortunately, the last two substances were found to be toxic, and they had to be taken off the market. A few decades later, in the 1950s, chlorofluorocarbons dominated the industry. But when they were found to deplete the ozone layer in the 1980s, the popular group of refrigerants was strictly regulated and later limited.

Modern Times

Because they are considered less harmful to the environment, hydrochlorofluorocarbons (HCFC) and hydrofluorocarbons (HFC) are the most popular groups of refrigerants today. With that said, a recently rediscovered substance may give them both a run for their money. One of the most abundant gases on Earth, carbon dioxide (CO2) has numerous industrial applications. In fact, it has been used as a refrigerant since the mid-nineteenth century. After decades of trial and error, modern CO2 systems are slowly becoming more commonplace. In the near future, they will finally appear in commercial establishments — most notably in supermarkets.

The Pros

The commercial production of CO2 systems is expected to become a reality very soon. With widespread manufacturing and installation, they are predicted to be a less expensive option. And when CO2 units are up and running, they will be cheaper to operate than most other refrigerants. Not to mention the fact that carbon dioxide has little to no ozone depletion potential. This means that CO2 is not a regulatory liability, as are HFCs, so there is no need to worry about future restrictions. Last but not least, carbon dioxide does not need to be reclaimed, and there is no need to account for the amount used.

The Cons

As perfect as it may seem, carbon dioxide cannot rightly be called an ideal refrigerant. The main obstacle to widespread industrial use has always been the relatively high working pressures of CO2 refrigeration. This added pressure increases the risk of breakdowns and premature wear. Current design changes have limited these risks but have added to the price tag in the process. The inevitable result is that CO2 systems have been on average more expensive than most other refrigeration systems and impractical for many commercial applications. Engineers have been working to address these challenges, and affordable, durable models are expected to enter the market in the near future.

The Bottom Line

The evolution of commercial refrigerants has led us to the most sustainable system yet. Carbon dioxide refrigeration will soon be the system of choice for gas stations, food production companies, and possibly even homeowners, as it will save users money in the long run. At prices of only around $1 per pound, the natural substance is one of the most affordable refrigerants on the market. It is also nonflammable, nontoxic, and readily available. Even with the higher capital costs, high-volume users can experience significant cost savings. It is no wonder CO2 systems have gained a lot of enthusiasm of late, particularly in the food retail industry. We can’t wait to see what the future holds for CO2!