5.2 Ammonia in Supermarkets

The number of supermarkets that use ammoniabased refrigeration systems in concert with CO2 and possibly glycol as a secondary fluid is quite low – probably under 20 worldwide. In the U.S., for example, there are only five stores with these systems while in Europe, there are three (and possibly more).99, 106, 107

The reason for this is twofold: fear and cost. The fear stems from ammonia’s toxic properties as well as the noxious odor it exudes; an ammonia leak is not something that most grocers would happily contemplate. Their assumption is that local building authorities are also not kindly disposed toward ammonia systems.

As for cost, ammonia/CO2 systems typically run 150% higher than that of conventional DX super- market systems.106

However, it turns out that because the amount of ammonia used in supermarket systems is minimal and confined to the machine room or on the roof, local fire marshals don’t typically have a problem with it. Moreover, in many cases, these systems have been found to be extremely efficient, saving the retailer a considerable amount in electricity costs.107

In the U.S., the most recent installation of an ammonia/CO2 system was in April 2020 by Raley’s at a new 55,000ft2 (5,109.7m2) store in Sacramento, California.108 The ammonia/CO2 system that Raley’s selected for this initial installation is different from those used by the other four U.S. stores in several respects. One is the way CO2 is employed. While the other stores use a cascade system that includes CO2 compressors for low-temperature cases, Raley’s has opted for a CO2 compressor-free pumped liquid-overfeed system. (Raley’s and the other systems all use pumped overfeed for medium-temperature cases.)

Ammonia/CO2 systems will likely remain a niche application in supermarkets. But if the safety record of the pilot stores remains positive and their energy savings become better known, they may yet become a significant factor in the marketplace.