Understanding and Optimizing Advanced Refrigeration Systems - CTS

The commercial and industrial refrigeration landscape is changing due to pressures to reduce global warming potential (GWP) and ozone depletion potential (ODP) of refrigerants. In response to these changes, manufacturers are producing new technologies which are designed to accommodate the required changes, and provide equivalent or improved efficiency, capacity and overall performance. Ammonia is a well-established and efficient refrigerant which has limitations in the form of mild toxicity and flammability. This project seeks to perform laboratory evaluations of several new packaged refrigeration systems to understand their performance and viability in refrigerated warehouse and walk-in cooling applications.

At the time this assessment was conducted, low-charge ammonia, which is specifically for packaged units, was a newer technology recently introduced to the market and intended to offer low-temperature refrigeration performance using a natural refrigerant, typically ammonia. Applied properly, it may offer better performance than operating large central plants. It also keeps the amount of required ammonia at low levels, enhancing overall onsite safety and reducing other costs. Typical ammonia or Hydrofluorocarbon (HFC) refrigeration systems involve large central engine rooms and long piping runs with large vessels on both the low pressure and high pressure sides of the system. It is reasonable that these can contribute to higher energy usage, losses, and maintenance costs as compared to packaged low-charge systems. For central plants, large ammonia charges are required, the regulation of which is increasingly tightened. Today, packaged systems are available from a variety of manufacturers that offer low- or zero-Global Warming Potential (GWP) choices. Parasitic loads and pressure losses can reduce efficiency in large central plants. Central engine rooms take from four to six months to install, and take up space that could be used to generate significant revenue. Moreover, centralized plants must be custom engineered and designed for each facility, as compared with standardized, lower-cost packaged systems. And owners are at high risk due to the large ammonia charges and extensive piping runs throughout the facility, which may occasionally leak ammonia. During normal operation, the refrigerated warehouse inventory is stored in temperature-controlled rooms that can be set to operate as either freezers or as coolers. This is a changing end-use combination involving moving product in and out of the space, and is generally driven by the specific warehouse inventory mix at any given time, which in turn determines the specific amount of frequent, unforeseen changes in energy consumption. These common, dynamic operational requirements cause frequent demand and energy changes (both increases and decreases) over short periods. The final report covers the findings of an assessment completed1 in the fall of 2019, and describes the results of laboratory testing three (3) packaged low-charge ammonia systems. Units that were new to the market were not compared to any baseline industry-standard practice. • Report lab testing findings for three packaged low-charge units. • Compare lab results to available field data of similar packaged low-charge refrigeration technologies. • Provide summary opportunities, recommendations, market barriers, and potential SCE programs relevant to the technology.   Refer to the final report for more details including conclusions and recommendations.