Consider the lifecycle of a head of lettuce: The lettuce is grown, it is harvested, it is transported to be cleaned and wrapped, it is shipped to a grocery store to be displayed, and it is sold. Then, the consumer transports the lettuce home and stores it until it is ultimately eaten. Throughout this multi-step process and over many miles and time, the lettuce must stay cold in order to be fresh, safe and, most importantly, tasty for consumption.

While electricity already plays a large role in cooling processes, there is room to create more efficiencies in the cold chain.

At a testing project in Berkeley, Calif., Takara Sake USA — the largest manufacturer of sake in the United States — uses a natural-refrigerant ammonia-based process cooling system. Effective temperature control is an important part of sake making. As part of the sake fermentation process, heat is released. At the same time, the temperature of the processing facility must remain constant so that the beverage can be fermented appropriately. To do this, the fermentation tanks must be continuously cooled.

Prior to the testing project, Takara Sake USA utilized an existing water-cooled chiller with R-507A hydrofluorocarbon (HFC) refrigerant to cool its fermentation tanks. The cooling system being tested incorporates new technology in a low charge ammonia chiller. The technology provides the following advances:

  • Ammonia is a natural refrigerant, which is a naturally occurring compound. It has zero global warming or ozone depletion potential.
  • It uses an ultra-low charge of ammonia refrigerant. This eliminates or reduces many regulations that otherwise govern the use of ammonia in industrial plants.
  • It uses an air-cooled condenser instead of water-cooled or evaporatively cooled condensers, which saves water resources.
  • It incorporates advanced microchannel condensers, an emerging technology that helps reduce refrigerant charge.
  • It includes a semi-hermetic compressor with no mechanical seal between the compressor and compressor motor. This makes the use of low-dose ammonia safer.

The project, conducted by Electric Power Research Institute (EPRI) and supported by California Energy Commission’s Electric Program Investment Charge program, is well underway. It is expected that the cooling system will prove to be 20 percent more efficient than comparable HFC-based process cooling systems.

Evolving technologies such as low charge ammonia refrigeration systems will become more widely used, in part because HFC refrigerants are scheduled to be phased out in the near future. The project system also will provide water savings, which is important for the drought-prone state of California. Further, the entire system is prepackaged, factory charged, and brought to a site as an integrated package, simplifying installation and driving cost efficiencies.

The approach to the cold chain in this manufacturing process removes HFC gases —major contributors of greenhouse gas — while using less electricity. Thus, it produces fewer carbon dioxide (CO2) emissions in the production of that electricity and eliminates the use of water resources.

Effective temperature control

Effective temperature control is an important part of many process cooling applications. During fermentation and aging from products such as sake and wine, careful temperature control ensures successful processing.

With successful efficiency results from these cooling systems used in the project test, EPRI and California Energy Commission’s Electric Program Investment Charge program could consider implementing similar technology in many other applications. Opportunities exist to use these cooling methods throughout every stage of the cold chain. Beyond the food industry, it is possible that with continued testing, one day we may be able to cool buildings with this same low charge ammonia approach.

To continue driving these advancements forward, it is important for stakeholders to understand that efficient electrification is not about increasing energy use. Instead, its goal should be increasing the efficiency of electricity by being smarter about how we use energy in order to drive other goals such as sustainability.

The Takara Sake USA project is just one example of how efficient electrification can directly benefit the process facilities using process cooling. PC