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18 January 2022
Food logistics – too much energy bills? Designing new facilities – what technology is optimal?

Listen to the whole thing below.

In previous columns, I wrote about the general principles of designing refrigeration installations in logistics centers and about the optimization potential of existing F-gas installations.

As a refrigeration engineer, I am fortunate to work during the greatest technological change in refrigeration since the end of World War II. One by one, industries are saying goodbye to “freons” and replacing them with r744 refrigeration (CO2 – carbon dioxide). At the outset, it should be noted that it is not possible to convert an old installation into a new one for CO2. So we are talking about setting up a new refrigeration system from scratch.

In the range of average temperatures, i.e. from 0 to +12C on CO2, we have power from 3 kW to 3MW, which corresponds to facilities with an area of ​​15 to 15,000 m2. In the low temperature range (-18 to -24C), the available power ranges from 3 to about 800 kW, i.e. chambers from 15 to 4,000 m2. It should be noted that there is a possibility of further expansion of the available cooling capacities.

The total cost of the refrigeration system consists of:

– CAPEX – purchase price

– OPEX – operating costs consisting of electricity consumption and servicing

– Risk – the likelihood of unforeseen costs in the future or the construction of an installation that does not meet the Customer’s requirements. We will not take risk into account in this column -> although managing it properly can be very profitable

As the most profitable in the ESMS, we mean the installation with the lowest total CAPEX + OPEX costs for 10 years. As I will show below, BEP (Break Even Point) can and should be much less than this time.

Below I have presented a comparison of electricity consumption by the most popular refrigeration systems.

Assumptions MT: 1000 kW, LT: 200 kW

  • The r448a system is based on separate MT and LT aggregates, working on good parameters, such as those set in the facility after optimization, which I wrote about in an earlier column.
  • r744 is a basic booster with parallel compressors
  • R744 – ejectors. It is equipped with liquid and gas ejectors

If we take r448 system energy consumption = 100% as a reference, r744 primary refrigeration will use 27% less energy and r744 with ejectors 34% less energy. This corresponds to annual savings of PLN 525,000 and PLN 658,000.

Additional costs incurred for more energy-efficient systems will be recouped after 2.4 or 2.7 years.

Other energy-saving technologies to mention:

  • Floor heating freezes with glycol heated by heat recovery from the refrigeration system
  • Defrosting with glycol heated by heat recovery from the refrigeration system. It is also a very effective method, especially in cold stores.
  • Installation of air curtains

Formal issues.

Pursuant to the regulation of the EU Parliament 517/2014, from January 1, 2022, refrigerants such as the above-mentioned r448a must not be used in commercial installations. I leave the interpretation of “commercial installation” to the reader and officials.

Therefore, it is optimal to install CO2 – r744. At this point, I would like to warn the reader against simplifying the choice of refrigeration system to the simple term “CO2”. Unfortunately, in my practice, I see projects that have more in common with sparkling water than with energy efficiency, and the reason for this is both too poor definition of technical requirements and too (naively) lowering CAPEX.

That’s why I emphasize: energy-efficient refrigeration must not only be CO2, but also well designed and carefully made! Like a banana…